Category: national parks

Phytophthora here, Phytopthora there … level of threat is unclear

Mt. Triglav – highest peak in the Slovenian (Julian) Alps; photo by Gunter Nuyts via Pexel

Scientists have discovered sizable diversity of pathogenic Phytophthora species in Europe, specifically in the Alps of northeastern Italy and western Slovenija.  They have also named a new species, and noted the need to change the definition of species previously named. See Bregant et al. – full citation at the end of this blog – open access!

Two of its findings are especially important for the US

First, the authors document the vulnerability of alpine areas to 18 Phythophthora species. Most of the plant hosts they studied have congenerics in mountainous areas of North America: Acer, Alnus, Betula, Fagus, Fragaria, Fraxinus, Ilex, Juniperus, Larix, Lonicera, Lycopodium, Pinus, Populus, Quercus, Rhododendron, Rubus, Salix, Sorbus, Taxus, and Vaccinium.

Second, the paper discusses how junipers are at particular risk. I remind you that P. austrocedrii has recently been detected in nurseries in Ohio and Oregon. This is another non-native Phythophthora that attacks junipers. I hope authorities are actively seeking to determine whether P. austrocedrii is present in nurseries or natural systems in other parts of the country.

The genus Phytophthora includes many serious plant pathogens, from the one that caused the disastrous potato blight of Ireland (Phytophthora infestans) to globally important forest-destroying invasive species, e.g., P. cinnamomi and “sudden oak death” P. ramorum.

Bregant et al. surveyed 33 small tree, shrub, and herbaceous plant species in 54 sites on the Italian island of Sardinia and the Alps of both northeastern Italy and western Slovenija. Altitudes varied from the valley bottom (700 m) to above tree line (2100 m). Sites included typical forests, riparian ecosystems, and heathlands.

The 360 isolates taken from 397 samples belonged to 17 known Phytophthora species. Some species are widespread and well-known, e.g., P. pseudosyringae. Three isolates belonged to a putative new species described by Bregant et al. – Phytophthora pseudogregata sp. nov. This total of 18 taxa was unexpectedly high. Many of the species are able to cause aerial infections via production of caducous sporangia. These can infect various organs of the plant host: fruits, leaves, shoots, twigs and branches; and cause necrosis and rots. They detected 56 new host–pathogen associations. All are listed, by type of host, in Tables 4 – 6 of the paper.

The surprising diversity and detection of taxa previously described in Australia (see below) illustrate   scientists’ still poor understanding of this genus. They also confirm fears that the global phytosanitary system is unable control intercontinental movement of Phytophthora.

The authors express concern because Alpine and subalpine regions are important hotspots for floral biodiversity. The great variation in altitude, aspect, moisture regimes, etc. – including extreme conditions – results in many different habitats on small spatial scales, with large numbers of both plant species and endemics in very confined spaces. The pathogens they discovered are spreading and compromising the biodiversity of these ecologically fragile habitats.

The authors say their study emphasizes the need to assess the full diversity of Phytophthora species and the factors driving the emergence and local spread of these invasive pathogens. They specify studying the Phytophthora communities on fallen leaves to evaluate host specificity, geographic distribution and survival strategies of the main Phytophthora species detected in this study. They report that scientists are currently mapping the distribution of the new species, P. pseudogregata, in the Alpine habitats and trying to establish its natural host range.

another view of the Julian Alps; photo via Rawpixl

Bregant et al. point out that increased scientific interest over the last 30 years has led to discovery of several previously unknown Phytophthora species and pathogen-host associations. They note that all but two of the taxa in one taxonomic grouping, Sub-clade 6b, have been described in the last 12 years. The majority of taxa have been described from forest ecosystems. This trend is depicted in Figure 8 of the article. This figure also displays which species were isolated from nurseries, agricultural systems, and forest ecosystems.

Results by Plant Type – Disease incidence was highest in shrub vegetation, alpine heathlands and along the mountain riparian systems. The most impacted ecosystems were heathlands dominated by common juniper & blueberry, and riparian systems dominated by alders. In these ecosystems, the Phytophthora-caused outbreaks had reached epidemic levels trend with a high mortality rate. On shrubs and heath formations, disease was initially observed in small areas and progressively spread in a concentric manner affecting more plant species.

Hosts and Diseases – Table 3 in the article lists the 33 host plant species, briefly describes the symptoms, and in some cases provides incidence and mortality rates. Those hosts described as suffering “sudden death” included Alnus viridis, Calluna vulgaris, Genista corsica, Juniperus communis, Lycopodium clavatum, Pinus mugo,Rhododendron ferrugineum, Salix alpine, Vaccinium myrtillus and Vaccinium vitis-idaea

Role of P. pseudosyringae – The most common and widespread species detected was P. pseudosyringae. It constituted more than half of the isolates (201 of the 360). Also, it infected the highest number of hosts (25 out of 33, including all three plant types). It was isolated at 36 of the 54 sites distributed throughout all geographic regions. Seventeen of the host–pathogen associations were new to science. (See Tables 4-6, in the paper.)

Vaccinium myrtillis – a vulnerable host; photo by Tatyana Prozovora via Wikimedia

P. pseudosyringae dominated disease agents in the shrub community, especially among high-altitude shrubs and heaths, e.g., blueberry, dwarf pine, juniper, rhododendron, and alpine willows. Bregant et al. note that these shrubs are extremely low-growing (an adaptation to high elevation conditions). This form might favor attack by Phytophthora sporangia and zoospores present in fallen leaves. Vaccinium myrtillus suffers particularly severe disease – as previously reported in Ireland. In their laboratory studies, Bregant et al. found P. pseudosyringae to be highly aggresse on common juniper (Juniperus communis), producing wood necrosis and shoot blight only four weeks after inoculation.

The importance of P. pseudosyringae in mountainous regions has been found in previous studies in Asia, Europe, and North and South America. However, the authors call for further study of certain aspects of the species. These regard infectivity and survival of the species’ sporangia in infected tissues fallen to the ground; and the ability of oospores to persist for years in environments subject to extreme low temperatures. The former could increase the risk of outbreaks and promote faster disease progression.

The authors suggest P. pseudosyringae’s survival stems from its production of very large and thick-walled chlamydospores. This reported feature is in contradiction with the original species description, which prompts Bregant et al. to call for a correction.

Other Species, Old and New – P. cactorum was the only Phytophthora species other than P. pseudosyringae detected on all three types of hosts (small trees, shrubs, and herbaceous plants). Phytophthora plurivora was the second-most isolated species. It was detected on 12 hosts in 24 sites.

The new putative species — Phytophthora pseudogregata sp. nov. – was detected on Alnus viridis, Juniperus communis, and Rhododendron ferrugineum. As noted above, scientists are now testing whether other plant species are also hosts. It was detected at two sites in Italy — Borso del Grappa and San Nicolò di Comelico; and one site in Slovenija.

Juniperus communis; photo by Joan Simon via Flickr

Diseases of Juniper – Koch’s postulates have been fulfilled, demonstrating that eight Phytophthora species – the new P. pseudogregata sp. nov. as well as P. acerina, P. bilorang, P. gonapodyides, P. plurivora, P. pseudocryptogea, P. pseudosyringae, P. rosacearum – are pathogenic on common juniper (Juniperus communis). The lesions caused by P. pseudosyringae were significantly larger than those caused by other species. Lesions caused by P. pseudosyringae, P. plurivora and acerina progressively girdled the twigs causing shoot blight, browned foliage & wilting symptoms.

Most Threatening Phytophthora clades – The most-frequently isolated Phytophthora species belong mainly to clades 1 and 3 – including P. pseudosyringae. Bregant et al. say these species have several advantages for surviving in mountainous ecosystems: they produce caducous sporangia useful for aerial infections and they tolerate relatively low temperatures. Twoother species in clade 3 were isolated only from the mountains of Sardinia. One, P. psychrophila, was isolated from bleeding cankers on an oak species, Quercus pubescens. Its geographic distribution and impact are still unknown. A second species, P. ilicis, is a well-known pathogen on various hollies in Europe and North America.

Four species belonging to subclade 1a were isolated in the Alps of northeastern Italy and Slovenija. P. cactorum is a widespread polyphagous pathogen found from tropical to temperate climates. It has been responsible for severe diseases on agricultural crops and forest trees. Its occurrence in cold areas has recently been reported in Europe and Australia. The recently described P. alpina has the highest ability to survive in extremely cold conditions. It was detected on four hosts – Alnus viridis, Lonicera alpigena, Vaccinium myrtillus, and V. vitis-idaea.

Some species, e.g., P. hedraiandra and P. idaei, were reported for the first time in natural ecosystems in Europe. They have previously been linked to root and foliar disease in agricultural and ornamental nurseries.

The second-most common species in the Bregant et al. study, P. plurivora, was isolated from 54 symptomatic samples from 12 plant species; eight of the hosts are new. It is common in forest ecosystems of Central Europe – which is now considered to be its region of origin. Little is known about the closely related P. acerina. To date, the latter has been detected widely in agricultural systems, nurseries, forests, and ornamental trees in northern Italy and Sardinia. It is much more rarely found elsewhere. Both P. acerina and P. plurivora are already known to be primary pathogens involved in decline of common and grey alder in Italy.

Five of the Phytophthora species in this study, including the new species P. pseudogregata, are in Clade 6. These include pathogens very common in European forests, e.g., P. bilorbang and P. gonapodyides. Others have more limited or still unknown distributions, e.g., P. amnicola and P. rosacearum. These five species’ ability to cause aerial infections on mountain vegetation might warrant re-evaluation of the reputation of species in this clade being saprophytes or only occasional weak opportunistic pathogens.

P. pseudogregata – in sub-clade 6a – was originally described in 2011 in wet native forests in Australia and on dying alpine heathland vegetation in Tasmania. It has recently been reported in the Czech Republic and Finland. The related P. gibbosa is known to occur only in Australia, where it is associated with dying native vegetation on seasonally wet sites.

Two species of clade 8 — P. kelmanii & P. syringae — have a very limited distribution. A third – P. pseudocryptogea — is widespread in Italian ecosystems from Mediterranean areas to the tree line in the Dolomites. One species from clade 7 (P. cambivora) isolated, mainly from stem bleeding cankers of small trees and shrubs. It has two mating types; bothoccurr in the Alps of northeastern Italy and neighboring Slovenija — on Alnus incana, Laburnum alpinum and Sorbus aucuparia.

SOURCE

Bregant, C., G. Rossetto, L. Meli, N. Sasso, L. Montecchio, A. Brglez, B. Piškur, N. Ogris, L. Maddau, B.T. Linaldeddu. 2024. Diversity of Phytophthora Species Involved in New Diseases of Mountain Vegetation in Europe with the Description of Phytophthora pseudogregata sp. nov. Forests 2023, 14, 1515. https://doi.org/10.3390/f14081515 https://www.mdpi.com/journal/forests

Posted by Faith Campbell

We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.

For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at  https://treeimprovement.tennessee.edu/

or

www.fadingforests.org

Forest Regeneration — Need to See Holistic Picture

red maple; via Pixabay

Research scientists in the USFS Northern Region (Region 9) – Maine to Minnesota, south to West Virginia and Missouri – continue to be concerned about regeneration patterns of the forest and the future productivity of northern hardwood forests.

The most recent study of which I am aware is that by Stern et al. (2023) [full citation at the end of this blog]. They sought to determine how four species often dominant in the Northeast (or at least in New England) might cope with climate change. Those four species are red maple (Acer rubrum), sugar maple (Acer saccharum), American beech (Fagus grandifolia), and yellow birch (Betula alleghaniensis). The study involved considerable effort: they examined tree ring data from 690 dominant and co-dominant trees on 45 plots at varying elevations across Vermont. The tree ring data allowed them to analyze each species’ response to several stressors over the 70-year period of 1945 to 2014.

In large part their findings agreed with those of studies carried out earlier, or at other locations. As expected, all four species grew robustly during the early decades, then plateaued – indicative of a maturing forest. All species responded positively to summer and winter moisture and negatively to higher summer temperatures. Stern et al. described the importance of moisture availability in non-growing seasons – i.e., winter – as more notable.

snow in Vermont; Putnypix via Flickr

The American Northeast and adjacent areas in Canada have already experienced an unprecedented increase of precipitation over the last several decades. This pattern is expected to continue or even increase under climate change projections. However, Stern et al. say this development is not as promising for tree growth as it first appears. The first caveat is that winter snow will increasingly be replaced by rain. The authors discuss the importance of the insulation of trees’ roots provided by snow cover. They suggest that this insulation might be particularly necessary for sugar maple.

The second caveat is that precipitation is not expected to increase in the summer; it might even decrease. Their data indicate that summer rainfall – during both the current and preceding years – has a significant impact on tree growth rates.

Stern et al. also found that the rapid rise in winter minimum temperatures was associated with slower growth by sugar maple, beech, and yellow birch, as well as red maple at lower elevations. Still, temperature had less influence than moisture metrics.

Stern et al. discuss specific responses of each species to changes in temperatures, moisture availability, and pollutant deposition. Of course, pollutant levels are decreasing in New England due to implementation of provisions of the Clean Air Act of 1990.

They conclude that red maple will probably continue to outcompete the other species.

In their paper, Stern et al. fill in some missing pieces about forests’ adaptation to the changing climate. I am disappointed, however, that these authors did not discuss the role of biotic stressors, i.e., “pests”.

They do report that growth rates of American beech increased in recent years despite the prevalence of beech bark disease. They note that others’ studies have also found an increase in radial growth for mature beech trees in neighboring New Hampshire, where beech bark disease is also rampant.

For more specific information on pests, we can turn to Ducey at al. – also published in 2023. These authors expected American beech to dominate the Bartlett Experimental Forest (in New Hampshire) despite two considerations that we might expect to suppress this growth. First, 70-90% of beech trees were diseased by 1950. Second, managers have made considerable efforts to suppress beech.

Stern et al. say specifically that their study design did not allow analysis of the impact of beech bark disease. I wonder at that decision since American beech is one of four species studied. More understandable, perhaps, is the absence of any mention of beech leaf disease. In 2014, the cutoff date for their growth analysis, beech leaf disease was known only in northeastern Ohio and perhaps a few counties in far western New York and Pennsylvania. Still, by the date of publication of their study, beech leaf disease was recognized as a serious disease established in southern New England.

counties where beech leaf disease has been confirmed

Eastern hemlock (Tsuga canadensis) and northern red oak (Quercus rubra) are described as common co-occurring dominant species in the plots analyzed by Stern et al. Although hemlock woolly adelgid has been killing trees in southern Vermont for years, Stern et al. did not discuss the possible impact of that pest on the forest’s regeneration trajectory. Nor did they assess the possible effects of oak wilt, which admittedly is farther away (in New York (& here) and in Ontario, Canada, west of Lake Erie).

In contrast, Ducey at al. (2023) did discuss link to blog 344 the probable impact of several non-native insects and diseases. In addition to beech bark disease, they addressed hemlock woolly adelgid, emerald ash borer, and beech leaf disease.

Non-native insects and pathogens are of increasing importance in our forests. To them, we can add overbrowsing by deer, proliferation of non-native plants, and spread of non-native earthworms. There is every reason to think the situation will only become more complex. I hope forest researchers will make a creative leap – incorporate the full range of factors affecting the future of US forests.

I understand that such a more integrated, holistic analysis might be beyond any individual scientist’s expertise or time, funding, and constraints of data availability and analysis. I hope, though, that teams of collaborators will compile an overview based on combining their research approaches. Such an overview would include human management actions, climate variables, established and looming pest infestations, etc. I hope, too, that these experts will extrapolate from their individual, site-specific findings to project region-wide effects.

Some studies have taken a more integrative approach. Reed, Bronson, et al. (2022) studied interactions of earthworm biomass and density with deer. Spicer et al. (2023) examined interactions of deer browsing and various vegetation management actions. Hoven et al. (2022) considered interactions of non-native shrubs, tree basal area, and forest moisture regimes.

See also my previous blogs on studies of regeneration in New Hampshire, North Carolina, National parks in the East, Allegheny Plateau and Ohio, and the impact of deer.

SOURCE

Stern, R.L., P.G. Schaberg, S.A. Rayback, C.F. Hansen, P.F. Murakami, G.J. Hawley. 2023. Growth trends and environmental drivers of major tree species of the northern hardwood forest of eastern North America. J. For. Res. (2023) 34:37–50 https://doi.org/10.1007/s11676-022-01553-7

Posted by Faith Campbell

We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.

For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at  https://treeimprovement.tennessee.edu/

or

www.fadingforests.org

Good News!!!! Treatments to Counter Beech Leaf Disease — at least for indidividual trees

beech leaf disease symptoms; photo by Matthew Borden via Flickr

Beech leaf disease (BLD) came to attention in 2012 near Cleveland. It has since spread to the Atlantic – Maine to New Jersey and northern Delaware; south into Virginia; north in Ontario; and west to eastern Michigan.

Scientists have scrambled to understand the disease – how it hijacks the tree’s metabolism;  & here its impacts on seedlings, saplings, and mature trees; how it spreads, locations at greatest risk.

(Maryland detections too recent to be shown)

Many of us have despaired.

Now Bartlett Tree Research Laboratories – the research arm of Bartlett Tree Experts – has announced development of Integrated Pest Management (IPM) strategies to treat individual trees – sadly not yet beech in the forest. The project is led by Dr. Andrew Loyd and Dr. Matthew Borden.

Seeing the disease’s impacts on a tree species with aesthetic and ecological values not easily replaced, and its rapid spread, scientists at Bartlett Tree Research Laboratories began testing fungicides and nematicides registered under the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) by the U.S. Environmental Protection Agency (EPA) to see whether they might be effective against the causal nematode Litylenchus crenatae ssp mccannii.

As Drs. Loyd and Borden note, managing BLD presents numerous challenges:

1. The disease was discovered recently, so there were many unknowns, including how it spreads and the causal organism’s novel life cycle.

2. The damage occurs in leaf buds during winter dormancy. There has been little previous research on such a system. It is difficult for chemicals to reach the tissues.

3. Mature trees are large, so reaching the vulnerable leaves in the canopy is difficult.

4. Treatment efficacy cannot be evaluated until nearly a year after application.

5. Few chemicals are registered for use against foliar nematodes or for trees in forest, nursery, or landscape settings.

6. Obtaining funding is difficult because protecting beech is a low priority among many of the usual sources.

Fortunately, the leadership at Bartlett – the company’s research department, the New England Division leadership, and especially Robert A. Bartlett, Jr. (head of the family-owned company) – saw the importance of protecting beech and have supported this research. The USDA Forest Service has also funded some of studies exploring soil drenches. Cameron McIntire reports that these studies do not yet have results.

Furthermore, Bartlett has chosen to make the science easily available to all interested parties. Three posters explaining experiments to date are available at ResearchGate. They have also published a study on the early tests of Fuopyram as a foliar spray. It is open-access. Additional publications presenting data on experiments with both spray (Fluopyram) and injection (Thiabendazole/Arbotect) are in preparation.

I summarize briefly here their findings as of August 2024.

In all the trials, the scientists judged efficacy of treatments by counting the number of viable nematodes in leaves, viable nematodes in overwintering buds, and BLD symptom severity at appropriate times before and after treatment (spray or injection).

Tests of foliar sprays on small to medium sized trees

The first tests of foliar applications that resulted in BLD suppression were carried out in Ohio starting in 2021, then expanded to other field sites in Ohio and several states in New England in 2022 and 2023 seasons. In early trials, trees were sprayed four times starting in mid to late July at 21-day intervals. The scientists say that recent trials focus on application timing and rate. They hope that optimizing these factors will help generate new recommendations that are more sustainable while maintaining efficacy.

At the annual meeting of the American Phytopathological Society in July 2023, Bartlett announced that Fluopyram is an effective management tool to combat BLD – on smaller trees that can be treated using foliar application. There are several EPA-registered products, though only one, Broadform, has been so far been granted a section 2(EE) recommendation “For Control of Beech Leaf Disease on Beech Trees.”

Treatments are less effective in situations where the inoculum load is very high (for example, a very dense stand of infected trees); or where mature, untreated canopies hang over treated understory beech.

They suggest that managers focus treatments on high-value specimen beech, collection preservation, and potentially uncrowded mixed natural stands.

Treatments should be made by certified pesticide applicators who are familiar with the disease and treatment specifications. For the injection treatment, technical training and specialized equipment is needed. Bartlett arborists and plant health care specialists in locations affected by BLD have all been trained to perform the treatments, and some other arborists are doing BLD treatments as well using the same products.

Soil drench

Matt Borden said that they tested drenches with three different chemicals. The approach did not reduce nemtatode numbers sufficiently. However, as noted above, the Forest Service is funding additional tests exploring possible combinations of drenches with other actions, such as thinning. Discovering management options across a range of application methods (e.g., foliar, injection, drench) and modes of action is vital for a disease that covers such a broad range of locations and tree sizes and forms.

a macroinjection demonstration; photo by Matthew Borden via Flickr

Injections

Scientists injected Thiabendazole (TBZ) into beech on private land in three locations in Ohio and New Jersey. They tested two application rates and three application timings. They have two years of follow-up data for one site, one year for the others.

Key findings:

  • nematode numbers in buds in late winter consistently reflected foliar symptoms when the leaves opened.
  • Injections made before mid-July provided the greatest reduction in nemtatode numbers and best canopy improvement. Trees injected late in the season (30 August), after the nematode has begun dispersing from leaves to buds, exhibited some BLD symptoms the next year, but suffered less canopy dieback than controls.

Margery Daughtrey of Cornell said during a discussion of these finding that the trees’ persistence suggests that trees can tolerate some level of symptoms. Among other things, it might be possible to treat the trees less frequently than annually.

  • TBZ appears to provide at least two seasons of nematode suppression

Bartlett continues to monitor these trees to see how long the injected chemical suppresses nematode numbers and how long the tree remains healthy. They are also establishing new field sites to further optimize rate and timing.

TBZ – in a product called Arbotect 20-S – has been used to manage Dutch elm disease and sycamore anthracnose since the 1970s. However, it is also a well-known nematicide, previously used as an anti-parasitic drug in human and veterinary medicine. Once injected, TBZ protects the tree for more than one season. The injection technology (MACRO-Injection) has also been used for decades. It infuses the chemical directly into the tree’s vascular system; it does not rely on root uptake. Matt says injection does require take technical skill and the right equipment. To minimize the risk of the wound cracking and weeping, the injection should be done low on the side of the root flare, not on top.

While Arbotect 20-S has been registered for use in 48 states for many years, new labeling is required for its use in beech trees and against BLD. Special Local Needs labels, 24(C)s, have been granted by eight states – Connecticut, Massachusetts, Maine, New Jersey, New York, Pennsylvania, and Virginia. Registration in a ninth – Maryland – is in progress and Bartlett scientists are prepared to apply for several more. The problem is that only a limited number of these “special needs” labels may be issued, and BLD has expanded so far, and so rapidly, that it is already infesting beech in more states than may be covered by 24(C)s. Furthermore, 24(C) labels expire if not renewed. Most current 24(C)s will be active through 2028 – not ideal for a disease that will likely be with us long into the future. The product manufacturer (Syngenta) and distributor (Rainbow Ecoscience) are drafting a change to the main Arbotect 20-S label to add beech and the new nematode pest, but warn that EPA review and approval of amendments can take a very long time. Until then, we must resort to limited special local needs labels, and some states will miss out.

contrasting canopy transparency in beech treated with TBZ v. untreated controls; photo by Matthew Borden

One of the key scientists who developed these treatments for Dutch elm disease, R. Jay Stipes, professor emeritus at Virginia Tech, is quoted by Bartlett rejoicing that his work might help protect another tree species.

Matt believes the treatments will be effective if applied every 2-3 years. This approach would also spread out the cost – which will depend on the arborist but Dave Anderson of Rainbow Ecoscience estimated to be about $25 / inch of dbh.

It is always best to obtain an accurate diagnosis before treatment. The next step is talking through your options with a certified arborist or tree disease specialist. The “good” thing about BLD is that it is a progressive disease and will not kill a tree in a single year. Therefore, waiting until you know the disease is present or active locally is generally recommended.

Tree injection is better than foliar application where the latter is impractical (e.g., the tree is tall) or to reduce runoff, particularly near streams. Bartlett recommends treating any beech larger than 10 cm dbh by injection; smaller trees by foliar spray.

Treated trees should be sound, without serious decay, girdling roots, or other conditions that curtail uptake. Based on research results to date, they recommend treating the tree before mid-July. Bartlett is testing the results of injecting the shortly after full leaf expansion – early to mid-June. Bartlett scientists are testing several application rates to determine how long a single injection will suppress BLD. So far they have had good results from both low and moderate label rates (0.4-1.6 fl oz/inch DBH).

All the technical information re: research into treatments and recommendations for applying either the foliar or injection treatments has been provided by Dr. Matthew Borden of Bartlett Tree Research Laboratories. He can be reached at

mborden@Bartlett.com
https://www.bartlett.com/staff/matthew-borden-dpm

Dr. Borden says he is immensely grateful for the support that allows him and Dr. Loyd to travel widely to establish the BLD research sites and spend weeks collecting data each year with their team. Company founder Francis A. Bartlett established the Bartlett Tree Research Laboratories as a separate entity within the company, where capital is reinvested directly into stable, long-term support of scientific tree research and preservation. The model is well-suited to provide the flexibility and freedom needed to rapidly respond to emerging invasive species issues.


Posted by Faith Campbell

We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.

For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at https://treeimprovement.tennessee.edu/

or

www.fadingforests.org

Too Many Deer; Too Few Forest Seedlings & Wildflowers

white flowered trillium (Trillium grandiflorum); via PICRYL One of the “charismatic wildflowers” mentioned by Blossey and colleagues

Bernd Blossey, Darragh Hare, and Don Waller have published a plea that America’s federal government take the lead in formulating a new national program on managing deer. Otherwise, they fear that deer populations will not be reduced to ecologically sustainable levels. I find their argument convincing and well-sourced. I agree that Americans need to figure out how to address this threat. (The full citation is at the end of this blog).

First, Blossey and colleagues describe the damage caused by overabundant deer:

  • severe declines in populations of many native forest herbs and shrubs, probably including disappearing wildflowers;
  • their replacement by non-native species that are less palatable;
  • poor regeneration of many canopy hardwood species;
  • decreased forest resilience, lowering  forests’ ability to adapt to stressors, especially climate change;
  • decreased ability of forests to deliver benefits that are of increasing value to many people;
  • increased prevalence of wildlife and human diseases associated with the spread and size of  growing tick populations; and
  • people – and deer — killed vehicle accidents on roads.

The widespread impacts of white-tailed deer (Odocoileus virginianus) in forests of the East are well-documented (see my previous blogs for a few examples; scroll below the “Archives” to find “Categories”). Blossey and colleagues note examples of similar impacts in the West, attributed to elk (Cervus elaphus) and black-tailed and mule deer (Odocoileus hemionus).

The authors review the decimation of deer populations in earlier centuries and the efforts of state wildlife agencies to rebuild their populations during the 20th Century. The problem, in their view, is that federal and — especially — state wildlife agencies have retained their traditional focus on managing wildlife for recreational hunters. However, recreational hunters make up a small and shrinking proportion of all Americans. Many more people now engage in “non-consumptive” enjoyment of wildlife.

lack of regeneration in Rock Creek Park, Washington D.C.; photo by Sam Sheline, NatureServe, via Flickr

State agencies’ narrow focus might partly arise from fragmented authorities. Agencies other than wildlife departments are responsible for addressing some repercussions of overabundant deer. These include threats to human health, loss of agricultural crops.

For several reasons, Blossey and colleagues call for federal leadership.  They think that only a national strategy can address, in a holistic way, the interrelated deer, human health, forest, and biodiversity crises. The strategy’s goal should be to protect species that are in decline because of over-browsing by deer and to avoid further declines in environmental and human health.

The authors reason that states are tied to traditional constituencies. Also, they have difficulty acting across jurisdictional boundaries. Second, few state wildlife agencies have authority to protect plant and invertebrate species. Yet these are the taxa most directly affected by overabundant deer. Blossey and colleagues point out that, of the ~1,300 species listed under the federal Endangered Species Act, 942 are plants and 287 are invertebrates.

They point out that deer also suffer the effects of overpopulation. Chronic wasting disease is spreading. It causes a slow, agonizing death of affected animals. Another 2.1 million deer are killed each year in vehicle crashes. [According to the World Animal Foundation, the current number of deer killed in traffic crashes is 1.8 million — 300,000 fewer.) Again, these deaths are often gruesome. Finally, the principal population “control” now is death by starvation in winter. This, too, is cruel. 

Blossey and colleagues say that return of large predators, even where feasible, will not result in sufficient reduction in deer populations. Nor will encouragement of greater hunting pressure on does.

They note that the federal government owns nearly 30% of the United States’ terrestrial surface area. Management is divided among many agencies – National Park Service, Fish and Wildlife Service, Bureau of Land Management, USDA Forest Service, Department of Defense, and many smaller agencies.  Management approaches vary. However, it would be possible to bring them into agreement – although, in some cases, this would require new legislation.

Another issue requires resolution:  federal agencies’ authority to manage wildlife on federal land.. The states have repeatedly claimed constitutional and legal authority to manage (vertebrate) wildlife on the federal lands within their borders. This assertion was countered years ago by Nie et al. (2017):

‘Federal land management agencies have an obligation, not just the discretion, to manage and conserve fish and wildlife on federal lands. … [M]ost states have not addressed the conservation obligations inherent in trust management; rather, states wish to use the notion of sovereign ownership as … a source of unilateral power but not of public responsibility. Furthermore, the states’ trust responsibilities for wildlife are subordinate to the federal government’s statutory and trust obligations over federal lands and their integral resources.’

Blossey and colleagues assert that managing wildlife (typically defined as mammals, birds, and fish) is much broader than establishing hunting seasons or methods. Furthermore, the concept of “public trust resources” means resources should be managed for all citizens, not just the fewer than 10% of US residents who hunt. A growing proportion of society expects this management to support healthy and diverse environments.

The authors stress that reducing deer overpopulations is necessary to meet numerous policy goals. These include fulfilling obligations under international treaties related to climate change, invasive species, and threatened species; restoring and conserving the nation’s forests to provide habitat; and adopting “nature-based” climate adaptations, such as carbon sequestration. They express the hope that recent presidential mandates to better quantify and value natural assets will increase awareness of the harm caused by deer overpopulation. Their proposed national strategy would develop goals and metrics to match specific environmental and human health outcomes.

Of course, management of deer must extend beyond federal property lines. This will require cooperation among states, Tribes, and private landowners.

The paper proposes the North American Waterfowl Management Plan as a model. Under this scheme the US Fish and Wildlife Service works with states, tribal governments, Mexico, and Canada to ensure accurate information on waterfowl populations a to calculate harvest levels. States implement their assigned quotas through their own regulations. Waterfowl hunters purchase Duck Stamps to fund the monitoring efforts. This program has worked well for most species covered by the program. Waterfowl are one of the few bird groups that have not declined dramatically.

Reducing deer populations will probably require lethal control. Studies indicate that at least 60% of does must be removed from a population to reduce herd sizes over time. Other means have been attempted at regional or larger landscape levels, such as sterilization, fertility control. These methods have failed even when paired with recreational hunting. Lethal approaches will probably distress many people. However, Blossey, Hare, and Waller believe the program would be supported if it is understood to be undertaken with the goal of improving the health of both humans and also the environment.

In the end, Blossey, Hare, and Waller say they are not willing to leave the killing to cars, disease, and starvation. They emphasize our moral responsibility to protect humans and the many other species that rely on diverse ecosystems. Our policies and choices created the problem, so we must try to correct it.

SOURCES

Blossey. B., D. Hare, and D.M. Waller, 2024. Where have all the flowers gone? A call for federal leadership in deer management in the US. Front. Conserv. Sci. 5:1382132. doi: 10.3389/fcosc.2024.1382132

Nie, M., C. Barns, J. Haber, J. Joly, K. Pitt and S. Zellmer. 2017. Fish and Wildlife Management on Federal Lands: Debunking State Supremacy. Environmental Law, Vol. 47, no. 4 (2017).

Posted by Faith Campbell

We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.

For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm

or

www.fadingforests.org

Birds v. mosquitoes: hope in Hawai`i

‘i‘iwi (Drepanis coccinea) – formerly very common from low to high elevations; photo by James Petruzzii_U

The endangered honeycreepers (birds) of Hawaiian forests are receiving the attention they deserve – and desperately need. There is good news! Promising and significant efforts are under way, matched to a recent strategic plan.  However, it is too early to know their results.

Nearly two and a half years ago, I blogged about efforts by a multi-agency consortium (“Birds, Not Mosquitoes” ). It was working to suppress populations of non-native mosquitoes, which vector two lethal diseases: avian malaria (Plasmodium relictum) and avian pox virus (Avipoxvirus). A single bite from an infected mosquito is enough to weaken and kill birds of some species, e.g., the ‘i‘iwi.

The threats from these diseases – and their spread to higher elevations as mosquitoes respond to climate change – pile on top of – other forms of habitat loss and inroads by other invasive species. All of the 17 species of honeycreeper that have persisted until now are listed as endangered or threatened under the federal Endangered Species Act. Four are in danger of extinction within as little as 1 – 2 years. These are ‘Akeke`e (Loxops caeruleirostris), ‘Akikiki (Oreomsytis bairdi)), Kiwikiu (Maui parrotbill, (Pseudonestor xanthophrys), and `Akohekohe (Palmeria dolei).

Akikiki; photo by Carter Atkinson, USGS

All these bird species are endemic to the Hawaiian archipelago — found nowhere else on Earth. They are already remnants. Nearly 80 bird species have gone extinct since people first colonized the Hawaiian Islands 1,500 years ago. Eight of these extinctions were recognized in October 2021.  Extinction of the final cohort would compromise the integrity of unique ecosystems as well as the Islands’ natural and cultural heritage.

I rejoice to report that the federal government has responded to the crisis. In late 2022 several Interior Department agencies adopted a multiagency Strategy for Preventing the Extinction of Hawaiian Forest Birds. The strategy specifies responsibilities for the key components of the program. These include: a) planning and implementing landscape-level mosquito control using Incompatible Insect Technique (IIT); b) translocating birds to higher elevation sites on other Hawaiian islands; c)  establishing captive populations of at-risk birds; and d) developing next-generation tools that increase the scope or efficacy of these actions. All these activities are being developed and conducted through intensive consultation with Native Hawaiians.

On August 8, 2023, the Secretary of Interior announced the allocation of $15,511,066 for conservation and recovery efforts for Hawaiian forest birds. About $14 million of the total was from the Bipartisan Infrastructure Law (Public Law 117-58). The funds are being channelled primarily through the U.S. Fish and Wildlife Service (FWS) ($7.5 million) and the National Park Service (NPS) ($6 million). Other sources of funding are the “State of the Birds” Program (FWS – $963,786); the national-level competitive Natural Resource grants program (NPS – $450,000); and the Biological Threats Program of the U.S. Geological Survey (USGS – $100,000).

What Is Under Way

I do worry continuing these efforts will be harder once their funding is subject to annual appropriations. However, they are a good start!

Steps have been taken on each of the four key component of the Strategy for Preventing the Extinction of Hawaiian Forest Birds:  

a) Planning and implementing landscape-level mosquito control using Incompatible Insect Technique (IIT – see below) to reduce the mosquito vector of avian malaria.

  • The Consortium has obtained all necessary state permits, regulatory approval of the approach by the U.S. Environmental Protection Agency, and done required consultations under the Endangered Species Act.
  • The Department of the Interior has funded a public-private partnership between the National parks and The Nature Conservancy (TNC) to develop, test, and carry out the first deployments of IIT. These occurred in May 2023 at high-elevation sites on the island of Maui. The next releases are planned for Kaua`i.
  • Consortium participants are carrying out the consultations and scientific preparations need to support the next deployment on the Big Island.

b) Translocating birds to higher elevation sites on the one island where they exist – Hawai`i.

  • Initial planning has begun to guide translocation of the endangered Kiwikiu (Maui parrotbill) and Akohekohe to higher-elevation, mosquito-free, habitats on the Big Island.

c) Establishing captive populations of the most at-risk species

  • To facilitate captive breeding of the four most endangered species, the two existing aviaries in Hawai`i need to be expanded. Space must be provided for at least 80 more birds. A contract has been signed for construction of this new aviary space.

d) Developing next-generation tools that increase the scope or efficacy of these actions.

  • Lab capacity has been expanded to monitor the effectiveness of IIT, as well as for developing next-generation mosquito control tools.
those who decide funding work here … & they work for us!!!!

The Incompatible Insect Technique (IIT) explained

The incompatible insect technique has been used successfully elsewhere to combat mosquitoes that transmit human diseases. Many insect taxa – including mosquitoes – harbor a naturally-occurring bacteria (Wolbachia). This bacterium has more than one strain or type. When a male mosquito with one type of Wolbachia mates with a female mosquito bearing a different, incompatible type, resulting eggs do not hatch. The IIT project releases male mosquitoes that have an incompatible strain of the bacterium than do local females. (Male mosquitoes do not bite animals seeking a blood meal, so releasing them does not increase the threat to either birds or people.) Implementation requires repeat treatment of sites at a cost of more than $1 million per site per year. It is hoped that this cost will fall with more experience.

Funding for the Strategy’s Four Components

As I noted above, much of the funding for these efforts has come from the Bipartisan Infrastructure Law (Public Law 117-58). Grants under this one-time statute are intended to cover project costs for perhaps five years. Other sources of funds are Congressional appropriations to Interior Department agencies under programs which presumably will continue to be funded in future years. These include the “State of the Birds” program; Endangered Species Act (ESA) implementation, especially its §6 Cooperative Endangered Species Conservation Fund; and State Wildlife Grants administered by the U.S. Fish and wildlife Service. However, funding under these programs is never guaranteed and competition is fierce. I hope participants – and the rest of us! – can be effective in lobbying for future funds required to save Hawaii’s birds from extinction.

a) Deploying IIT

Over Fiscal Years 2017 – 2021 (ending September 2021), Interior Department agencies supported the IIT program by:

  • Providing $948,000  to the State of Hawai`i from “State of the Birds”, State Wildlife Grants, and Endangered Species Act (ESA) §6;
  • The U.S. Fish and Wildlife Service  provided $545,000 plus staff time’ 
  • National Park Service  provided $1.2 million for IIT preparations at Haleakala National Park and surrounding state and Nature Conservancy lands
  • U.S. Geological Survey provided about $7.05 million in research on Hawaiian forest birds, invasive mosquitoes, and avian malaria.

The State of Hawai’i allocated $503,000 and employee staff time.

In addition,

  • the National Fish and Wildlife Fund provided a total of $627,000 in grants to TNC and American Bird Conservancy for Wolbachia IIT.
  • TNC committed to supporting some of the initial costs to deploy Wolbachia IIT for the first site in Hawai`i through a contractor (see below)
  • American Bird Conservancy provided funding for coordination and public outreach.

In FY2022 (which ended in September 2022),

  • NPS provided $6 million for on-the-ground work on Maui, also development and initial production of Wolbachia IIT.
  • Interior Department Office of Native Hawaiian Relations provided in-kind services to engage with Native communities’ members

b) Moving endangered birds to mosquito-free areas at high elevations on the Big Island

This is planned to begin by 2030. Interior committed unspecified funds to planning and consultation with Native Hawaiians.

c) Rearing captive birds

 FWS supports operation of the two existing aviaries through two funding channels: $700,000 annually provided directly to the aviaries, plus another $500,000 per year through ESA §6through the State of Hawai`i. The San Diego Zoo – which operates the aviaries — provides $600,000 – $800,000 per year in the form of in-kind services, staffing, veterinarians, and administrative support. Interior’s Office of Native Hawaiian Relations provided in-kind services to support to engagement with Native Hawaiian community members

d) Regarding exploration of “next-generation” mosquito control tools

The FWS provided $60,000 to a scientific laboratory to study precision-guided Sterile Insect Technique (pgSIT) tools to protect bird species threatened by avian malaria.

Funding for the portions of these programs dependent upon annual appropriations is uncertain. Current signs are promising: House and Senate bills to fund for the current year (Fiscal Year 2024) – which began in October 2023! – both support at least some aspects of the program. According to American Bird Conservancy, the Senate appropriations bill has allocated $2.5 million to parts of the program. According to the Committee report, the House appropriations bill allots $4.7 million to the State of the Birds program to respond to urgent needs of critically endangered birds. The report goes on to direct the FWS to “incorporate adaptation actions into new and revised recovery plans and recovery implementation strategies, such as with the mosquito vector of avian pox & malaria in the revised Hawaiian Forest Birds recovery plan. …” Per the report, the Appropriations Committee “continues to encourage the [NPS] to respond to the urgent landscape-scale needs of critically endangered forest birds with habitats in national parks.” The report then specifies species threatened by non-native mosquitoes carrying avian malaria and other pathogens. Finally, the report allocates $500,000 to the U.S. Geological Survey for research on the Hawaiian forest birds.

Meanwhile, the American Bird Conservancy is preparing to advocate for $20 million for FY25 through “State of the Birds” Activities and associated NPS and USGS programs. The details of this amount have not yet been laid out.

CISP will support this request and urges you to do so also. We will suggests ways to help when we know more.

Posted by Faith Campbell

We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.

For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm

or

www.fadingforests.org

Eastern National Parks: Forest Regeneration Failing in 69%

Gettysburg battlefield; now under attack by emerald ash borer (see below)

Kathryn Miller and colleagues (full citation at end of blog) have published a study that examined the status and trends of forest regeneration in 39 National parks from Virginia to Maine. Four-fifths of the forest plots in the study are classified as mature or late successional – so at first glance the forests look healthy. However, the researchers made an alarming finding: in 27 of 39 parks, forest regeneration is failing – either imminently or probably. Acadia National Park is an exception; it is the only park in the study experiencing healthy regeneration. They warn that without intense, sustained – and expensive! – intervention, these forests are likely to be converted to other types of ecosystems. [I  blogged recently about findings regarding regeneration in eastern forests: here  and  here  and here and here.

The forests’ understories have too few seedlings and – especially – saplings to maintain themselves. Worse, in many cases the seedlings and saplings are not the same species as the mature trees that form the canopy. The saplings are shorter species that never reach the canopy. That is, species like pawpaw (Asimina triloba), American holly (Ilex opaca), American hornbeam (Carpinus caroliniana), and eastern redbud (Cercis canadensis) are regenerating, rather than the oaks (Quercus spp.), hickories (Carya spp.), maples (Acer spp.), and pines (Pinus spp.) that constitute the canopies of mature forests in these parks.

Miller and colleagues call these “regeneration mismatches.” In about half of the parks, these native canopy tree species make up less than half of current saplings and seedlings. This situation suggests the forests’ species composition will shift substantially, thereby undermining resilience in the face of other challenges, such as invasive plants and pests and climate change.

In many of these National parks, Miller and colleagues found abundant ash regeneration. For example, ash (Fraxinus spp.) constitute more than half of all seedlings in four parks (Johnstown Flood and Friendship Hill in Pennsylvania; Catoctin Mountain in Maryland; Manassas Battlefield in Virginia).  Miller and colleagues consigned ash species to the “subcanopy class” because the emerald ash borer (EAB) has caused such high mortality of mature trees. They think regard it unlikely that current and future seedlings will ever reach full size. The devastating impact is most starkly illustrated in Gettysburg National Battlefield Park. Consistent deer management since 1996 has been rewarded: the Park ranks at the top for regeneration among the 39 parks. However, more than half of the seedlings and a quarter of the saplings are ashes. EAB has shifted the Park’s otherwise secure regeneration status into probable failure.

When regeneration fails:  too many deer

Throughout the study region, the overwhelming reason regeneration fails is browsing by overabundant deer. The level of deer browse is considered “acceptable” in only four parks. Deer suppress the number of seedlings and saplings. They also skew species composition of native subcanopy species toward those less palatable. Miller and colleagues found that canopy tree density and cover and past human land use had minimal impacts on seedling and sapling numbers or species composition.

Overabundant deer also promote invasion and spread of non-native plants, which are the second most important factor impeding regeneration. Together, invasive plants and non-native earthworms are ecosystem engineers that negatively impact soil and cause cascades of biotic and abiotic impacts throughout forest ecosystems.

Many of the parks experiencing the most severe impacts of chronic deer browse also have the highest invasions by non-native plants. A natural process of regeneration occurs when the death or collapse of mature trees create gaps in the forest canopy. Where deer and invasive shrubs overlap, this process is often hijacked. Instead of nearby native tree species accelerating their growth toward the canopy, thickets of invasive shrubs crowd the space.

For this reason, Miller and colleagues recommend that park management prioritize treating invasive plants in canopy gaps of disturbed stands to avoid forest loss. They recommend deliberate creation of canopy gaps to promote resilience only for parks, or stands within parks, that have low deer and invasive plant abundance or the capacity to intensively manage invasive plants in gaps.

In most parks, non-native tree species are rare, less than 2% of total regeneration. In seven parks, though, non-native trees exceed ten percent of seedlings and/or saplings. In three parks, saplings of non-native trees are increasing. These are primarily tree-of-heaven (Ailanthus altissima) and Norway maple (Acer platanoides). In Saratoga National Historical Park, seedlings of common buckthorn (Rhamnus cathartica) are increasing.

Beech regeneration in Prince William Forest Park

Role of other pests

Miller and colleagues express fear that beech bark disease and beech leaf disease might have effects similar to those of EAB, leading to a greater “regeneration debt” in parks where American beech (Fagus grandifolia) is the dominant regeneration component. They cite specifically Prince William Forest Park in northern Virginia, [25 mi2] Rock Creek Park in the District of Columbia, [2.7mi2] and Saratoga National Historical Park. [5.3 mi2] The authors also suggest that thickets of beech root sprouts formed in response to BBD can suppress regeneration of other native canopy species and so might need to be managed.

Miller and colleagues mention hemlock woolly adelgid (HWA), but provide very little information. They report that Saint-Gaudens National Historical Park in New Hampshire (the home and studio of sculptor Augustus Saint-Gaudens) is at particular risk because of growth of both beech and eastern hemlock (Tsuga canadensis). I know that Delaware Water Gap National Recreation Area [109m2] has experienced major losses of mature hemlocks. [Shenandoah National Park has also, but it was not included in the study.]

Hemlock Ravine, Delaware Water Gap National Recreation Area; photo by Nicholas T via Flickr

Miller and colleagues report that Acadia National Park is seeing recovery of red spruce (Picea rubens) from a major fire in 1947 and possibly also from acid rain. They do not mention the longer-term threat from the brown spruce longhorned beetle. Their focus is on forest dynamics largely unaffected by deer.

In the same way, the authors make no mention of the absence of dogwood trees, presumably because they had been eliminated by dogwood anthracnose decades ago. Nor do they mention vascular streak dieback of redbud; the causal agent still uncertain. [See Annie Self’s presentation to National Plant Board, August 2023.]

dead ash tree in Shenandoah National Park

One omission is large enough that it might affect the study’s findings. At mi2 Shenandoah is the largest National Park in the region. It was not included in the study because the Park’s forest monitoring process is not compatible with those in other NPS units. All the other parks – including Acadia (562 mi) – are much smaller, protecting historic sites like Civil War battlefields.

RECOMMENDATIONS

Miller and colleagues recommend that deer management be initiated in parks classified as at imminent or probable regeneration failure, if such programs are not already under way. They warn that effective deer management requires sustained commitment. Studies of deer exclosures show that full forest recovery from chronic deer overabundance can take as long as 40–70 years.

The authors also recommend actions to open the subcanopy to facilitate growth of saplings belonging to desired species. They caution that deer predation must be controlled. Furthermore, either invasive plant cover must be low, or management must ensure that that the park has sufficient resources to sustain an invasive plant control program – especially if invasive plants are combined with abundant deer.

Parks experiencing compositional mismatches and that are dominated by oak–hickory forest types might also benefit from prescribed burning. Again, deer browse pressure must be minimized. In addition, regeneration of oaks and hickories must already be present.

In park forests dominated by species vulnerable to lethal pests, e.g., beech-, ash-, or hemlock-dominated forest stands, Miller and colleagues recommend considering planting alternative native canopy species and protecting those plantings from deer. Park managers should also consider thinning beech thickets formed after beech bark disease kills canopy trees.

Media coverage

The Washington, D.C., public radio station, WAMU, reported on this research   on the air (broadcast December 20) and on its website. It is written by Jacob Fenston, with great photographs by Tyrone Turner. The story emphasized the link between deer and invasive plants – since regeneration in eastern deciduous forest happens by saplings taking advantage of gaps formed when mature trees die. The story quotes DC-area people on their efforts to contain vines. The Natural Resource Manager at Catoctin Mountain Park [8 mi2] describes that park’s longstanding deer control program. The story also mentions impacts of EAB and threat of BLD.

News – Funding for these parks to counter the threats!

Lead author Kathryn Miller has informed me that the Bipartisan Infrastructure Law and Inflation Reduction Act has provided the 39 parks involved in this study over $10 million to improve forest resilience largely through reduction of invasive plants and overabundant deer.

Of course, invasive species threats to National parks are not limited to the Northeast – nor are they new. I have raised this problem from the beginning. To see these blogs, on the “nivemnic” website, scroll down below the archives to the “categories”, then click on “national parks”.

SOURCE

Miller, K.M., S.J. Perles, J.P. Schmit, E.R. Matthews, M.R. Marshall. 2023. Overabundant deer and invasive plants drive widespread regeneration debt in eastern United States national parks. Ecological Applications. 2023;33:e2837. https://onlinelibrary.wiley.com/r/eap  Open Access

Posted by Faith Campbell

We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.

For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm

or

www.fadingforests.org

Sobering News: Invasive Grasses, Trees, and Killer Pests in Hawai`i

At CISP, our hearts go out to all those affected by the terrible August fires on Maui. May the departed rest in peace. May the living find comfort and all that is needed for recovery.

Fire and Invasive Grasses

A fire in non-native grasses on Maui in 2009; photo by Forrest and Kim Starr

Major U.S. and international media continue to detail the fires’ devastation, especially in Lahaina. As time has passed, more news has highlighted the role that the widespread presence of introduced, fire-prone grasses played in the rapid growth and spread of Maui’s fires.  

For example, The Washington Post devoted seven paragraphs in one story to the issue of grasses. The story quotes several experts: Alison Nugent, an associate atmospheric scientist at the University of Hawaii’s Water Resources Research Center; Jeff Masters, a meteorologist for Yale Climate Connections; and Clay Trauernicht, a fire researcher at the University of Hawaii.

These and others have been widely quoted in the many recent articles. I am glad that they – and the media – are making clear that climate change is not the sole factor causing damaging wildfires. It is clear that Maui’s recent weather patterns – including the high-velocity winds and drought – have been within the range of normal climate patterns. Fluctuations in the Pacific’s weather have also been normal, especially under the influence of the current El Niño.

The dangers caused by Hawai’i’s fire-prone grasses are also clear – and have been for years. Experts have identified policy weaknesses at the county and state level. Also, they have specified changes to land management that could better prevent or mitigate wildfires. There has been far too little action.

On the other hand, there are hopeful signs.

endangered ‘akikiki photo by Carter Atkinson, USGS

The Hawai’i Wildfire Management Organization, a nonprofit, is educating and engaging communities state-wide. Elizabeth Pickett, a Co-Executive Director, presented an overview of wildfire at the Hawai’i Invasive Species Awareness Month in February 2023. The Big Island Invasive Species Committee has successfully eradicated two species of pampas grass on Hawai’i Island – after 13 years’ work. A native species has been planted where pampas formerly grew.

Another Post article reported on efforts by staff and fire departments to protect the Maui Bird Conservation Center, which houses critically endangered Hawaiian birds found nowhere else on Earth, including some currently extinct in the wild. As I have blogged previously, the palila, kiwikiu, ‘akikiki, ‘alalā [Hawaiian crow; extinct in the wild] and other birds are dying from avian malaria, carried by nonnative mosquitoes.  The Center on Maui and another on the Big Island are run by the San Diego Zoo Wildlife Alliance. Conservationists have completed field trials of a proposed mosquito suppression process for Maui and are seeking public comments for a similar program on Kaua’i. These programs represent groundbreaking and long-awaited progress on countering a principal threat to the survival of Hawai`i’s unique avifauna. Loss of the Center and its birds would have devastated post-suppression efforts to rebuild and restore bird populations in the wild.

The Post carried a second story about the effort to protect Hawai`i’s endangered birds – a full page of print, even longer – with many photos, on the web. The article mentions the “Birds, Not Mosquitoes” program and varying views about it. I rejoice that the dire situation for the Islands’ biodiversity is getting attention in the Nation’s capital. Again, see my earlier blog.

Plant Invasions in Hawaiian Forests

A team of scientists from the USDA Forest Service and Natural Resources Conservation Service, plus the Hawaii Division of Forestry and Wildlife, has carried out a new assessment of the extent of invasive plant species in forests on the Hawaiian Islands (Potter et al. 2023; full citation at end of blog).

The results of their analysis are – in their words – “sobering”. They portend “a more dire future for Hawai`i`s native forests.”

First, regarding the recent fires, Potter et al. found significantly higher cover by invasive grasses on Forest and Inventory Analysis (FIA) plots on Hawai‘i and Maui than on O‘ahu, Kaua‘i, and Lana‘i. Grass invasions were particularly high on the eastern coast of Maui – near Lahaina. Even so, the authors say their study’s methods resulted in a gross underestimate of areas invaded by fire-prone grasses. That is, most of Hawai’i’s xerophytic dry forests were converted to grasslands before the FIA program began. Therefore these grasslands are not included in FIA surveys.  

Psidium cattleyanum; photo by Forrest and Kim Starr

The extent of current invasions in wetter forests is already significant – but trends point to an even more worrying future.

  • Naturalized non-native plant taxa constitute half of the Hawaiian flora.
  • 56% of Hawaii’s 553,000 ha of forest land contained non-native tree species; about 39% of these forest lands are dominated by non-native tree species. Invasive plant species of particular concern were found in the understory of 27% of surveyed forest plots.
  • Across all islands, six of the ten most abundant species are non-native: Psidium cattleyanum, Schinus terebinthifolius, Leucaena leucocepahala, Ardisia elliptica, Psidium guajava, and Acacia confusa.
  • While less than one-third (29%) of large trees across the Islands are non-native, this proportion increases to about two-thirds of saplings (63%) and seedlings (66%). Potter et al. focus on the likelihood that plant succession will result in transformation of these forests’ canopies from native tree species to non-native species.
  • 75% of forests in lower-elevation areas of all islands are already dominated by non-native tree species.  “Only” 31% of higher-elevation forests are so dominated. These montane forests have been viewed as refugia for native species, but all are invaded to some extent – and likely to become more degraded.
  • Potter et al. say the high elevation forests might be more resistant to domination by non-natives. Such a result would be counter to well-documented experience, though. Even the authors report that the montane rainforests and mesophytic forests of O‘ahu and Kaua‘i are heavily invaded by non-native tree species. Such species constitute 86% or more of large trees, saplings, and seedlings in mesophytic forests; 45% of large trees and 66% of seedlings in their montane rainforests.
  • The most abundant tree species in Hawai`i is the invasive species Psidium cattleyanum (strawberry guava). It was recorded on 88, or37%, of 238 FIA plots. There are nearly twice as many P. cattleyanum saplings as Hawai`i’s most widespread native species, ‘ohi’a lehua (Metrosideros polymorpha).
  • Widescale replacement of native trees by non-native species is likely. Several factors favor these changes: 1) tree disease – rapid ‘ohi’a death has had drastic impacts on ‘ohi’a populations on several islands; 2) invasions by forbs and grasses; 3) soil damage and other disturbances caused by invasive ungulates; and 4) climate change. If succession conforms to these trends, non-native tree species could eventually constitute 75% or more of the forest tree stems and basal area on all islands and across forest types and elevations. 

Loss of Hawai’i’s native tree species would be disastrous for biodiversity at the global level. More than 95% of native Hawaiian tree species are endemic, occurring nowhere else in the world.

The authors analyzed plant presence data from 238 FIA plots. Plots spanned the state’s various climates, soils, elevations, gradients, ownership, and management. However, access issues precluded inclusion of forests from several islands: Moloka‘i, Kaho’olawe, and Ni‘ihau. I know that Moloka‘i, at least, has a protected forest reserve (a Nature Conservancy property) at the island’s highest elevations.

Protecting Native Trees

Federal, state, and private landowners have carried out numerous actions to protect native forests. These efforts might be having some success. For example, forests on public lands, in conservation reserves, or in areas fenced to exclude ungulates were less impacted by non-native plants than unfenced plots, on average. However, the authors could not determine how much of this difference was the result of management or because protections were established in forests with the lowest presence of IAS species. Fencing did not prevent invasions by forbs and grasses – possibly because they are so widespread that seed sources are everywhere.

Hawaii’s two National parks (Hawai`i Volcanoes and Haleakala) have made major efforts to control invasive plants. Hawai`i Volcanoes, on the Big Island, began its efforts in the 1980s; Haleakala (on Maui) more recently. This might be one explanation for the fact that a smaller proportion of the forests on these two islands have been invaded. These efforts have not fully protected the parks, however. Low elevation native rainforests now have a high presence of non-native shrubs. Such forests on Hawai`i Island also have significant invasions by non-native woody vines, forbs and grasses.

More discouraging, intensive efforts have not returned lowland wet forest stands to a native-dominated state. Native tree species are not regenerating—even where there is plentiful seed from native canopy trees and managers have repeatedly removed competing non-native understory plants.

Potter et al. conclude that other approaches will be needed. They suggest deliberate planting of native and non-invasive non-native species or creation of small artificial gaps that might facilitate recovery of native tree species. In montane forests on Hawai`i and Maui, where native tree seedlings account for more than 70% of all tree seedlings, they propose enhancing early detection/rapid response efforts targetting invasive forbs. This would include both National parks.Certainly Haleakala National Park has this priority in mind. It launched a serious effort to try to eradicate Miconia calvescens when this tree first was detected.

Lloyd Loope, much-mourned scientist with US Geological Survey, attacking Miconia on Maui

Potter et al. note the challenge of managing remnant xerophytic dry forests, where natural regeneration of native plants has been strongly limited by invasive grasses; loss of native pollinators and seed dispersers; and the increasing frequency and intensity of droughts. They note that expanded management efforts must be implemented for decades, or longer, to be successful.

Native Trees at Risk to Nonnative Insects

Beyond the scope of the Potter et al. study is the fact that at least two dry forest endemic trees have faced their own threats from non-native insects.

The Erythrina gall wasp, Quadrastichus erythrinae, appeared in Hawai`i in 2005; it originates in east Africa. It attacks the endemic tree, wiliwili, Erythrina sandwicensis.  I believe a biocontrol agent, Eurytoma erythrinae, first released in 2008, has effectively protected the wiliwili tree, lessening this threat.

The Myoporum thrips, Klambothrips myopori, from Tasmania, was detected on the Big Island in 2009. It threatens a second native tree. Naio, (Myoporum sandwicense), grows in dry forests, lowlands, upland shrublands, and mesic and wet forest habitats from sea level to 3000 m. The loss of this species would be both a signifcant loss of native biodiversity and a structural loss to native forest habitats. The thrips continues to spread; a decade after the first detection, it was found on the leeward (dry) side of Hawai`i Island with rising levels of infestation and tree dieback.

Rhus sandwicensis on Maui; photo by Forrest and Kim Starr

Two native shrubs, Hawaiian sumac Rhus sandwicensis and Dodonea viscosa, might be at risk from a biocontrol agent in the future. APHIS has approved a biocontrol for the highly invasive Brazilian pepper, Schinus terebinthifolia. Brazilian pepper is the second-most abundant non-native tree species in the State. It was found on 28 of 238 (12%) FIA plots. However, the APHIS-approved biocontrol agent is a thrips—Pseudophilothrips ichini. It is known to attack both of these two native Hawaiian shrubs. The APHIS approval allowed release of the thrips only on the mainland US. However, many insects have been introduced unintentionally from the mainland to Hawai`i. Furthermore, Hawaiian authorities were reported to be considering deliberate introduction of P. ichini to control peppertree on the Islands.

In Conclusion

In conclusion, Potter et al. found that most Hawaiian forests are now hybrid communities of native and non-native species; indeed, a large fraction are novel forests dominated by non-native trees. Business-as-usual management will probably mean that the hybrid forests – and probably those in which the canopy is currently dominated by native species—will follow successional trajectories to novel, non-native- dominated woodlands. This likelihood results in a more dire future for native plants in Hawaiian forests than has been previously described.

Potter at al. hope that their findings can guide research and conservation on other islands, especially those in the Pacific. However, Pacific islands already have the most naturalized species globally for their size—despite what was originally considered their protective geographic isolation.

SOURCE

Potter, K.M., C. Giardina, R.F. Hughes, S. Cordell, O. Kuegler, A. Koch, E. Yuen. 2023. How invaded are Hawaiian forests? Non-native understory tree dominance signals potential canopy replacement. Landsc Ecol  https://doi.org/10.1007/s10980-023-01662-6

Posted by Faith Campbell

We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.

For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm

or

www.fadingforests.org

A Forest without Big Trees — Which Animals Will be Decimated?

In an earlier blog about tree extinctions, I commented that less drastic impacts by pests can also be important. I mentioned specifically that clumps of beech root sprouts cannot duplicate the quantities of nuts and cavities provided by mature beech trees.

This thought prompted me to search for information about use of tree cavities by wildlife. The articles I have found are decades old and largely focus on implications for management of forests for timber. Timber production conflicts with a goal of ensuring the presence of large (“overmature”), trees, especially those with dead branches, and completely dead trees (“snags”). These articles were written too long ago to address the possible impacts of non-native insects and pathogens – although there is some discussion of widespread mortality of pines caused by the mountain pine beetle.

These sources make clear that species that make cavities are keystone species. Many other wildlife species depend on them — birds, bats and terrestrial animals – mammals and herps. Furthermore, these cavity-associated species require forests with significant numbers of large, old, declining trees. When non-native insects or pathogens kill those trees, there might be a short-term bonanza of dying trees – suitable for nesting and foraging; and wood-feeding insects to provide food. But afterwards – for decades or longer – there will probably be small-diameter trees, and different species. Can the cavity-dependent species find habitat or food under these circumstances?

[By coincidence, the PBS program “Nature” broadcast an episode on woodpeckers on the 2nd of November! The title is “The Hole Story”. ]

Cavities provide a variety of habitats for many species – including some not usually thought of as “forest” species. Among the 85 North American bird species identified by Scott et al. as associated with cavities are seven species of ducks, two vultures, three falcons, 12 owls, two swifts, six flycatchers, two swallows, purple martin, seven chickadees, three titmice, four nuthatches, brown creeper, five wrens, three bluebirds, and two warblers. They point out that the majority of these birds are insectivores. Woodpeckers are especially important predators of tree-killing bark beetles.

Goodburn and Lorimer found that more than 40 species of birds and mammals in hardwood forests of Wisconsin and Michigan use cavities in snags and dead portions of live trees for nest sites, dens, escape cover, and winter shelter. Bunnell reported that 67 vertebrate species commonly use cavities in the Pacific Northwest. Chepps et al., Daily et al., and Wiggins focus on specific species in the Rocky Mountains. (Full citations for all sources are at the end of the blog.)

While Scott et al. (published in 1977) do not address the impact of non-native pests, their profiles of individual bird species sometimes name specific types of trees favored. Several of these tree taxa have been decimated by such non-native pests, or face such attack in the near future. Thus, concern appears warranted for:

pileated woodpecker; photo by Jo Zimni via Flickr
  • birds nesting in American elm, including two that are quite large so they require large trees to accommodate their nests: common goldeneye (a duck) and pileated woodpecker (larger than a crow).
  • the pileated woodpecker also nests in ash and beech and here
  • the yellow-bellied sapsucker nests in butternut.

How many species depended on American chestnut, which – before the blight — grew to diameters up to 5 feet, heights of 70 to 100 feet, and had hollow centers (USDA 2022)?

In the West, some nesting tree species are under imminent threat from invasive shot hole borers, goldspotted oak borer, or sudden oak death. Detection of the emerald ash borer in Oregon portends a longer-term threat. Birds likely to feel these impacts include the acorn woodpecker, ash-throated flycatcher, and purple martin. The golden-fronted woodpecker is associated with oaks in parts of Texas where oak wilt is severely affecting live oaks.

ash-throated flycatcher; photo by Mick Thompson via Flickr

At the beginning of the 21st Century – before widespread mortality caused by the emerald ash borer — densities of snags in the managed forests in the Lake States were apparently already insufficient to sustain population densities of cavity nesting birds. Pileated woodpeckers and chimney swifts both prefer snags greater than 50 cm dbh, which are significantly less abundant in harvested stands. For six of eight bird species studied, the number of breeding pairs was significantly higher in old-growth northern hardwood stands than in those under management (Goodburn and Lorimer).

Strong Primary Excavators are Keystone Species

Cavity nesters are commonly divided into:

1) primary excavators that excavate their own cavities. These are further divided into strong excavators – those species that forage by drilling, boring, or hammering into wood or soil; and weak excavators – those species that probe or glean bark, branches, and leaves to acquire prey.

2) secondary cavity users, that use holes made by primary cavity excavators (Bunnell).

Strong primary excavators tend to be large, e.g., most woodpeckers, sapsuckers, and the northern flicker. Weak excavators are mostly smaller species, such as chickadees and nuthatches; plus those woodpeckers that forage primarily by probing and gleaning, extracting seeds, or capturing insects in flight [e.g., acorn woodpecker (Melanerpes formicivorus), downy woodpecker (Picoides pubescens)] (Bunnell).

Bunnell considers strong excavators to be keystone species because so many other cavity users depend on them. Their loss would seriously disrupt forest ecosystems. For example, in the Pacific Northwest, only nine of 22 avian primary excavators are strong excavators. Another 45 species are secondary cavity users. These include waterfowl, tree swallows, and some mammals such as flying squirrels. Some cavity nesters support an even wider group of species: in the Pacific Northwest, at least 23 bird species, six mammal species, and numerous arthropods (nine orders and 22 families) feed on sap and insects collected at holes drilled by sapsuckers (Bunnell). [I discuss sapsuckers’ ecosystem role in greater detail later.]

Tree Characteristics

There is general agreement that animals dependent on tree cavities “prefer” (actually, require) trees that are large – tall, of large circumference, and sturdy – while having decayed interiors.

Size:

As Bunnell notes, larger snags provide more room and tend to stand longer without breaking, so they provide greater opportunities for cavity use. They also tend to be taller, so they offer higher nest sites that provide better protection from ground-dwelling predators. While larger-diameter trees remain standing longer regardless of the cause of mortality, snags created by fire usually fall sooner than do other snags. Beetle-killed trees are more attractive to cavity nesters that tend to excavate nest sites in trees on which they have foraged.

In the upper Midwest, cavity trees were a scare resource, even in unmanaged forests. Mean diameters for live cavity trees were twice as large as the mean diameter of the live trees in stands under a management regime. Such larger-diameter snags were more numerous in old-growth than in managed stands, especially in mixed hemlock-hardwood stands (Goodburn and Lorimer).

The Importance of Decay

Excavating a cavity demands considerable energy, so birds seek sites where a fungal infection has softened the interior wood. The exterior wood must remain strong to prevent collapse of the nest. These rots take time to develop, so they appear more often in older, even dying, trees. Bunnell, Scott et al., Chepps et al., and Goodburn and Lorimer all emphasize the role of decay in providing suitable cavity sites. Chepps et al. compared the aspen trees used by four species of cavity-nesting birds in central Arizona. Not only were nest trees softer than neighboring trees; they were softer at the spot where the nests were excavated than at other heights. [Spring (1965) provides a fun discussion of different species’ adaptations to the energy demands of hard pecking and climbing vertical trunks.]

Live v. Dead Trees

However, the need for decay does not necessarily mean birds prefer dead trees. Goodburn and Lorimer found that in Wisconsin and Michigan, a large percentage of all cavities found were in live trees.  

Bunnell found that strong excavators select trees with less visible signs of decay. Where possible, secondary users will also use live trees. However, intense competition often forces them to use dead trees.

Hardwoods v. Conifers

Bunnell states that deciduous trees more often contain internal rot surrounded by a sound outer shell than do conifers (at least this is true in the Pacific Northwest). He found that cavity nesters chose hardwoods for 80–95% of their nest sites even where hardwoods comprised only 5–15% of the available tree stems. He concluded that availability of living hardwoods had a significant influence on strong excavators in the West, although probably was less important in hardwood stands in the East.

Taxa Dependent on Other Types of Cavity

Some species depend on cavities created by forces other than bird excavations, such as decay or fire. These include most of the mammals, especially the larger ones e.g., American martens, fishers, porcupines, and black bears. These natural cavities are often uncommon. Vaux’s swifts nest and roost in hollow snags large enough that they can fly in a spiral formation to enter and leave (Bunnell).

little brown bat Myotis sp. photo by S.M. Bishop via Wikimedia Commons

Bats are a special case. Bats are unique among mammals of their size in having long lives, low reproductive rates, and relatively long periods of infant dependency. They also play a key ecological role as the major predators of nocturnal flying insects (van den Driesche 1999). Also many species are in perilous conservation status: half of the 16 bat species in British Columbia were listed as threatened or endangered as of 1998 (van den Driesche). This was before the deadly disease whitenose syndrome had been detected in North America.

Bats require larger trees. In the Pacific Northwest at least, that choice often means conifers (Bunnell). Roosts are difficult to find, so samples are small. A study on the west coast of Vancouver Island (van den Driessche), located only nine roosts despite searching during three summers. Five roosts were in large-diameter (old) western red cedar, with dead tops and extensive cracks.

Brown creepers and some amphibians and reptiles nest or seek cover under slabs of loose bark, which are typically found on dead or dying trees. The same large, mature and old-growth conifer trees also provide preferred foraging habitat, since there is a higher density of arthropod prey on their deeply furrowed bark. While Wiggins (2005) studied bird populations in the Rocky Mountains, he cited studies in the eastern United States, specifically in the Blue Ridge and Allegheny mountains, that have found similar results. Goodburn and Lorimer found that in National forests in Wisconsin and Michigan, only 15% of trees consisted of the necessary snags with loose bark plates. Suitable trees were most frequent old-growth hemlock-hardwood stands, and on larger-diameter snags. A high proportion of the snags with loose bark were yellow birch (Betula alleghaniensis).

Importance of foraging sites

As Bunnell points out, a bird must feed itself before it can nest. Foraging trees and snags are usually smaller than nesting trees. Furthermore, birds need many more foraging sites than nesting sites. The situation perhaps most pertinent to our usual focus on invasive pests concerns bird species’ response to mountain pine beetle outbreaks. Red-breasted nuthatches and mountain chickadees increasing dramatically in apparent response to the beetle epidemic. When most of the conifers had been killed, and numbers of beetles diminished, numbers of these bird species also declined–despite the increased availability of conifer snags for nesting. Indeed, the birds continued to nest primarily in aspen during the epidemic.

Bunnell reiterates that snags of all sizes are needed; they provide perching, foraging, and hawking sites for bird species beyond cavity nesters as well as sustenance for bryophytes, insects, and terrestrial breeding salamanders. He says more than 200 studies reported harvesting of standing dead trees in beetle-killed forests had negative effects on bird, mammal, and fish species.  

Other Dependencies – Food Sources

yellow-bellied flycather; photo by Dennis Church via Flickr

A few studies looked at the role of cavity-creating birds in providing food sources. The focus was on sapsuckers. They drill sapwells into trees’ phloem; sap flowing into these wells attracts many other species. In Michigan, Rissler determined that yellow-bellied sapsuckers’ sapwells attracted insects in seven orders and 20 families, especially Coleoptera, Diptera (other than Tephritidae), bald-faced hornets, and Lepidoptera. Daily et al. (1993) cites other studies showing that ruby throat and rufous hummingbirds have extended their breeding ranges by relying on these sapwells for nutrition in early spring before flowers open. [The “Nature” program covers this behavior.]

In a subalpine ecosystem in Colorado, Daily et al. found that red-naped sapsuckers support other species in two ways. First, they excavate nest cavities in fungus-infected aspens that are utilized by at least seven secondary cavity nesting bird species. When they feed, they drill sapwells that nourish more than 40 species – including hummingbirds, warblers, and chipmunks. Daily et al. called this a keystone species complex comprised of sapsuckers, willows, aspens, and a heartwood fungus. Disappearance of any element of the complex could cause an unanticipated unraveling of the community.

Goodburn and Lorimer looked at the availability of downed wood but did not discuss the implications of the presence of only small-diameter coarse woody debris.

Efforts to Accommodate Biodiversity Needs

Scott et al. reported in 1977 that the USDA Forest Service had required staff at regional and National Forest levels to develop snag retention policies. Twenty years later, Goodburn and Lorimer noted that Forest Service management guidelines for some Wisconsin and Michigan National forests since the early 1980s have called for the retention of all active cavity trees and  5-10 snags (larger than 30 cm dbh)/ha. However, as I noted above, they fear that these recommended snag retention levels might still be too limited to support cavity nesters. They found that two species that prefer snags greater than 50 cm dbh, pileated woodpeckers and chimney swifts, were significantly more abundant in old-growth than in selection stands. Furthermore, the number of breeding pairs of six species was at least 30% higher in old-growth northern hardwood than in selection stands and more than 85% higher in selection cuts than even-aged.

Goodburn and Lorimer cited others’ findings that removal of some live timber and snags in an Arizona ponderosa pine forest reduced cavity-nesting bird populations by 50%. Species affected were primarily violet-green swallows, pygmy nuthatches, and northern three-toed woodpeckers.

Female mountain bluebird by Jacob W. Frank. Original public domain image from Flickr

As I noted, none of these experts has addressed the impacts of wide-spread pest-caused tree mortality. If I may speculate, it seems likely that when the first wave of mortality sweeps through a forest, the result might be an expansion of both nesting opportunities (in dead or dying trees) and food availability for those that feed on wood borers. These would probably be more plentiful even in trees killed by pathogens or nematodes. Sapsuckers and those that depend on them might experience an immediate decline in sap sources. Over the longer term it seems likely that all cavity-dependent species will confront a much lower supply of large mature trees. I note that many deciduous/hardwood tree species are being affected by introduced pests.

Are there current studies in Michigan, where so many ash have died?

SOURCES

Bunnell, F.L. 2013. Sustaining Cavity-Using Species: Patterns of Cavity Use and Implications to Forest Management. Hindawi Publishing Corporation. ISRN Forestry. Volume 2013, Article ID 457698

Chepps, J., S. Lohr, and T.E. Martin. 1999. Does Tree Hardness Influence Nest-Tree Selection by Primary Cavity Nesters? The Auk 116(3):658-665, 1999

Daily, G.C., P.R. Ehrlich, and N.M. Haddad. 1993. Double keystone bird in a keystone species complex. Proc. Natl. Acad. Sci. USA Vol. 90, pp. 592-594, January 1993 Ecology

Goodburn, J.M. and C.G. Lorimer. 1998. Cavity trees and coarse woody debris in old-growth and managed northern hardwood forests in Wisconsin and Michigan. Can. For. Res. 28: 427.438 (1998)

Rissler, L.J., D.N. Karowe, F. Cuthbert, B. Scholtens. 1995. Wilson Bull., 107(4), 1995, pp. 746-752

Spring, L.W.  1965. Climbing and Pecking Adaptations in Some North American Woodpeckers.

Scott, V.E., K.E. Evans, D.R. Patton, C.P. Stone. 1977. Cavity-Nesting Birds of North American Forests. Agriculture Handbook 511 USDA Forest Service. https://www.gutenberg.org/files/49172/49172-h/49172-h.htm

United States Department of Agriculture, Animal and Plant Health Inspection Service. Draft Enviromental Impact Statement. 2022. State University of New York College of Enviromental Science and Forestry Petition (19-309-01p) for Determination of Nonregulated Status for Blight-Tolerant Darling 58 c’nut (Castanea dentata)

van den Driessche, R., M. Mather, T. Chatwin. 1999. Habitat use by bats in temperate old-growth forests, Clayoquot Sound, British Columbia 

Wiggins, D.A. (2005, January 27). Brown Creeper (Certhia americana): a technical conservation assessment. [Online]. USDA Forest Service, Rocky Mountain Region. Available: http://www.fs.fed.us/r2/projects/scp/assessments/browncreeper.pdf [date of access].

Posted by Faith Campbell

We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.

For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm

or

www.fadingforests.org

Firewood – How to Change Risky Behavior

The Nature Conservancy (TNC) and Clemson University have analyzed how to persuade people not to move firewood – and the tree pests that can accompany it. (Full citation at the end of this blog) Their study is based on five surveys conducted by TNC between 2005 and 2016. These surveys guided TNC’s “Don’t Move Firewood” campaign and its outreach efforts since the beginning in 2008

As Solano et al. note, wood-boring pests continue to enter the country and spread, causing immense damage. Firewood transport by campers is a significant contributor to that spread. Millions of individuals decide whether to move firewood. Yet the scientific literature is quite limited regarding their behavior and TNC’s survey data has never been published.

The patchwork of state and federal quarantines is largely reactive and has failed to prevent continuing spread. The regulatory regime has been further fragmented by APHIS’ deregulation of the emerald ash borer.  As a consequence, limiting the spread of pests depends even more on educating campers to behave responsibly – voluntarily.

The TNC’s surveys each focused on different geographic areas and asked different questions in each. So their compilation cannot show trends in awareness or other measures. Nevertheless, the authors find:

  • Most people in the United States don’t know firewood can harbor invasive forest insects and diseases, but when targeted by effective education they can learn and are likely to change their behavior.
  • The two best ways to reach the public is through emails confirming campsite reservations and flyers handed out at parks. Web-based information seemed less effective. However, most of the surveys were done before 2011, the year when 50% of adults reported using internet media.
  • Forestry-related public agencies (especially state forestry departments) are the most trusted sources of information about forest health issues.
  • It works better to “push” information, not expect people to seek it on their own.
  • Messages should focus on encouraging the public to make better choices, including how they, themselves, will benefit. Positive, empowering calls to action, like “Buy it Where You Burn It” or “Buy Local, Burn Local” are better than negative messages, such as “Don’t Move Firewood”.
  • People respond to messages that emphasize protecting forest resources, e.g., ecosystem services like clean water. They response less to messages about forest threats.
Hungerford Lake Recreation Area at Equestrian Campground. Original public domain image from Flickr

Solano et al. describe the ways that different socioeconomic groups differ in their awareness of forest pests and in how they respond to various statements about forests, pests, and messengers. The focus is on how to overcome four psychological barriers to changing behavior that had been identified in a study of climate change. In the firewood context, those barriers were: 1) lack of awareness; 2) mistrust and negative reactions to the messengers; 3) habit; and 4) social comparison, norms, conformity, and perceived poor quality of purchased firewood.

From this work, the authors suggested further work::

  • Development of education and outreach programs that target those with lower education levels, since, on average, ~60% of people who camp did not graduate from college. Further research is probably needed to identify the most effective messengers and messages.
  • While 80% of the survey respondents were over 40, the proportion of campers made up of Gen X and millennials is increasing. Managers need to improve outreach for younger audiences. This includes engaging the messengers they trust: scientists, environmentalist politicians, peer networks, and social media.
  • While women trust the USDA Forest Service and conservation organizations, 55% of campers in a given year are men. Further research is needed to clarify the most effective messengers and messages for men. The outreach agencies should select the messengers that both sexes trust. 
  • Levels of awareness should be assessed both before and after implementing new educational strategies so that the strategies’ effectiveness can be determined.

Since 80% of the respondents were white, determining the most effective messages and messengers for other ethnic groups also seems necessary, although the authors did not address this.

SOURCE:

Solano, A., Rodriguez, S.L., Greenwood, L., Rosopa, P.J., and Coyle, D.R. 2022. Achieving effective outreach for invasive species: firewood case studies from 2005-2016. Biological Invasions.
https://link.springer.com/article/10.1007/s10530-022-02848-w

You can read the article – but not download it – at https://rdcu.be/cRRVH 

To request a copy of this study from the author, contact the lead author at Clemson University.

Posted by Faith Campbell

We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.

For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm

or

www.fadingforests.org

More & bigger ships, deeper ports = more pests?

Port of Houston – Bayport Container Terminal; photo by Ray Luck via Flickr

The U.S. continued to import large amounts of goods from Asia in the first three months of 2022. During this period, total volume imported from Asia increased to 1.62 million TEU — 31.1% higher than in the same period in pre-pandemic 2019 (Mogelluzzo, B. April 22, 2022).

Due to congestion in West Coast ports, the proportion of Asian goods entering the country through East Coast and Gulf Coast ports also rose in the first quarter of 2022 compared to the same period in 2021: by about 33% along the Atlantic and 6% along the Gulf (Mogelluzzo, B. April 22, 2022). Increases were particularly steep in the south: 9.2% at Savannah; 12.5% at Norfolk; 26% at Charleston; and an astonishing 52.1% through Houston.

Due to Covid-19-related port and factory shutdowns in China, a rising share of imports to the U.S. in 2022 came from other countries in Asia. Imports grew especially from Vietnam but also Thailand, Malaysia, Indonesia, and South Korea (Wallis, K. May 11, 2022).

Port of Long Beach Pier G – ITS – MOL vessel; photo by port authority

Starting in May 2022, West Coast ports began to recover their dominant role – probably because East Coast and Gulf Coast ports were now suffering their own congestion-related delays. Virtually all the restored traffic entered through the Los Angeles-Long Beach port complex; these ports imported a monthly record of 851,956 TEU from Asia in May. Imports through Seattle and Tacoma actually declined from the previous month, while Oakland’s imports from Asia remained steady (Mongelluzzo, June 15, 2022).

Thus, the “baseline” for US imports from Asia each month is now 20 to 30% higher than it was before COVID-19 disrupted supply chains (Mongelluzzo, June 15, 2022).

East Coast Ports Deepening and Expanding to Accept Larger Ships

Meanwhile, East Coast ports continue efforts to deepen their channels and expand their infrastructure so that they can service the larger container ships.

In late June 2022 the US Army Corps of Engineers approved the plan by the Port of New York-New Jersey (PANYNJ) to dredge channels to accommodate more post-Panamax ships. The largest ship that has called at NY-NJ was 16,000 TEU; port officials hope to accommodate ships up to 21,000 TEU, apparently using current capacity (Angell, June 23, 2022; Angell, May 27, 2022). PANYNJ Port Director Bethann Rooney says the port expects to see annual volumes rise to 17 million TEU by 2050, almost double its throughput in 2021 (Angell, May 27, 2022).

The Corps found the PANYNJ plan to be both environmentally and economically sound. The Corps will now seek Congressional funding for the project in the 2024 Water Resources Development Act; the Port Authority will also contribute to the project (Angell, June 23, 2022).  We need to be more active in commenting on these port expansion environmental assessments!

The Port of NY-NJ is also seeking to expand storage facilities for incoming shipping containers. Several sites are at various stages of consideration and development; one – part of the “Port Ivory” site on Staten Island – includes a tidal wetland.  A November 2021 application by PANYNJ a change-in-use permit is under review by New York State Department of Environmental Conservation (NYSDEC) (Angell, May 27, 2022). Can those interested in environmental protection express their opposition?

The Port of Charleston is expected to finish dredging its inner harbor and channel this year. Last year, the Port of Virginia has received initial funding for a dredging project that should be completed by 2024 (Angell, May 27, 2022).

As we know, numerous tree-killing insects have been introduced from Asia to the ecologically similar forests of eastern North America – often in wood packaging. ALB in Charleston These include Asian longhorned beetle, emerald ash borer, redbay ambrosia beetle, phytophagous and Kuroshia shot hole borers (for profiles of each visit here). Indeed, 15 of 16 non-native bark beetles in the Xyleborini (a tribe of ambrosia beetles) detected in the United States since 2000 are from Asia (Bob Rabaglia, USFS Forest Health Protection, presentation at IUFRO meeting in Prague, September 2021).

Growing numbers of containers entering Atlantic and Gulf Coast ports raises the risk of additional introductions. Insects associated with imports from semi-tropical ports in Vietnam entering the U.S. through Gulf or southern Atlantic ports might well find these regions hospitable. I worry, for example, about the polyphagous and Kuroshio shot hole borers – surely the Gulf Coast provides a more suitable environment for insects from Vietnam and Taiwan than does southern California? And known hosts are present – box elder, willows, sweetgum, mimosa, tree of heaven …

Of course, containers are then sent on from the ports to distribution centers – presenting opportunities for pest introductions in inland areas. New or expanded distribution centers include Atlanta and Appalachian Regional Port and Statesboro Airport in Georgia, Rocky Mount, North Carolina; Huntsville, Alabama; Portsmouth and Front Royal, Virginia (Ashe and Angell July 5, 2022). Front Royal is at the northern end of Shenandoah National Park!

photo by Daveylin via Flickr

European Trade

Meanwhile, U.S. imports from Europe continued at high levels – although they were not breaking records. In the first half of 2022, the U.S. imported just under 1.77 million TEU from Europe. The largest category of commodity from Northern Europe was foodstuffs — 410,930 TEU. Machinery and mechanical products imports – the type of good often associated with infested wood packaging – numbered 228,521 TEU. Vehicles, aircraft, and vessels imports were 107,526 TEU. “Miscellaneous manufactured articles” that include furniture, bedding, mattresses, and light fittings were 132,979 TEU. I expect – although the source does not so state – that this last category includes decorative stone and tile – again, a category often associated with infested wood packaging.

 While fewer damaging pests have been introduced from Europe in recent decades, the risk remains.

Updated Haack Analysis

As has been documented repeatedly (e.g., my blogs, including 248), the current approach to curtailing pest introductions associated with wood packaging is not sufficiently effective. Customs officials continue to detect live quarantine pests in wood packaging as it enters the country. However, the exact level of this threat is unclear since the only assessment was based on data from 2009 (Haack et al., 2014).  I eagerly await the results of Bob Haack’s updated analysis, which I hope will be published soon.

SOURCES

Angell, M. NY-NJ port lays groundwork for larger ships ahead of dredging. May 27, 2022.  https://www.joc.com/port-news/us-ports/port-new-york-and-new-jersey/ny-nj-port-lays-groundwork-larger-ships-ahead-dredging_20220527.html

Angell, M. NY-NJ deepening study gets US Army Corps blessing. June 23, 2022. https://www.joc.com/port-news/us-ports/port-new-york-and-new-jersey/ny-nj-deepening-study-gets-us-army-corps-blessing_20220623.html?utm_campaign=CL_JOC%20Ports%206%2F29%2F22%20%20%20REDO_PC00000_e-production_E-140850_SA_0629_0900&utm_medium=email&utm_source=Eloqua

Ashe, A. and Angell, M. Rising volumes slowing port flow on East, Gulf coasts. July 5, 2022. https://www.joc.com/port-news/us-ports/rising-volumes-slowing-port-flow-east-gulf-coasts_20220705.html?utm_source=Eloqua&utm_medium=email&utm_campaign=CL_JOC%20Daily%207%2F6%2F22%20NONSUBSCRIBER_PC015255_e-production_E-141183_KB_0706_0617

Knowler, G. Rising US imports keep pressure on trans-Atlantic. July 18, 2022.  https://www.joc.com/port-news/international-ports/rising-us-imports-keep-pressure-trans-atlantic_20220718.html?utm_source=Eloqua&utm_medium=email&utm_campaign=CL_JOC%20Daily%207%2F19%2F22%20NONSUBSCRIBER_PC015255_e-production_E-141796_KB_0719_0617

Mongelluzzo, B. Q1 US imports from Asia show no slowing in consumer demand. Apr 22, 2022. https://www.joc.com/maritime-news/container-lines/q1-us-imports-asia-show-no-slowing-consumer-demand_20220422.html

Mongelluzzo, B. U.S. imports from Asia surge to unexpected record in May. June 15, 2022. https://www.joc.com/port-news/us-ports/us-imports-asia-surge-unexpected-record-may_20220615.html?utm_source=Eloqua&utm_medium=email&utm_campaign=CL_JOC%20Daily%206%2F16%2F22%20NONSUBSCRIBER_PC015255_e-production_E-140076_KB_0616_0617

Wallis, K. Asia shippers plug trans-Pacific export gap from China COVID-19 disruption. May 11, 2022.

https://www.joc.com/maritime-news/trade-lanes/asia-shippers-plug-trans-pacific-export-gap-china-covid-19-disruption_20220511.html?utm_source=Eloqua&utm_medium=email&utm_campaign=CL_JOC%20Daily%205%2F12%2F22%20NONSUBSCRIBER_PC015255_e-production_E-137446_KB_0512_0617

Posted by Faith Campbell

We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.

For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm

or

www.fadingforests.org