a blight-resistant chestnut tree bred using traditional breeding techniques by The American Chestnut Foundation; photo by F.T. Campbell
Nearly one-third of the continental United States is covered by forests, more than 1 million square miles. As demonstrated by many authorities and – I hope! – in my blogs, these forests face increasing threats, including introduction of rising numbers of non-native insects and pathogens that kill or severely damage the tree species that comprise those forests.
One response has been a request by the U.S. Endowment for Forestry and Communities, the Environmental Protection Agency, and U.S. Department of Agriculture (Agricultural Research Service, Animal and Plant Health Inspection Service, U.S. Forest Service, and National Institute of Food and Agriculture) that the National Academies of Sciences, Engineering, and Medicine consider the potential for the use of biotechnology to mitigate these threats to forest health.
The resulting report was released in January 2019 (see full citation at the end of the blog). The report is 240 pages long, very thorough, and wide-ranging. It does have a 12-page summary, listing the Panel’s many conclusions and its recommendations. While the preponderance of the report concerns forests on the North American continent, the panel did seek information about threats to endemic trees in Hawai`i, which (to my mind) are especially severe. See earlier blogs here and here.
To me, one of the report’s most important conclusions is that while there are multiple options for dealing with forest pests, their feasibility and success vary widely. Saying that no single management practice is likely to be effective by itself, the report calls for increasing investment in the full range of strategies other than biotechnology, i.e.,
- preventing arrival of non-native pests (recognized as the first line of defense and the most cost-effective strategy);
- site management practices;
- biocontrol; and
- enhancement of genetic resistance naturally present in affected tree species (including developing human capital in professions related to tree breeding).
The panel was not asked to examine the potential for biotech to reduce threats to forest health by altering the pests affecting North American tree species so it does not do so.
Summarizing the Threat
Citing Aukema et al. 2010 and other sources, the Academy panels reports that approximately 450 species of insects and at least 16 species of pathogens have been introduced and have established in continental U.S. forests. Of those, 62 insects and all of the pathogens are determined to have a high impact. A USDA Forest Service study estimates that 81.3 million acres (about 7% of all forested or treed land in the U.S.) are at risk of losing at least 25% of tree vegetation by 2027 due to insects and pathogens. These pests are both non-native, introduced species and native pests that are spreading to new regions as a result of climate change.
The Academy panel notes that loss of a tree species can have cascading adverse effects on the forest ecosystem and on the range of services it provides and the values it represents to human populations.
Part A. The Technology for Trees
The Academy panel was asked to assess the ecological, economic, and social implications of deploying genetically engineered trees. The experts also were asked to identify the knowledge needed to evaluate the ways such a tree might affect the prospects for forest health. The analysis was to include social and cultural impacts as well as impacts on forest and associated ecosystems – including their structure, composition, processes, function, productivity, and resilience.
This use of biotechnology to restore healthy forests differs from applications in industrial plantations or annual agricultural crops in that the biotech tree is intended to proliferate in a natural forest setting.
The authors chose four taxa — American chestnut (Castanea dentata), whitebark pine (Pinus albicaulis), ash (Fraxinus spp.), and poplars (Populus spp.) — to illustrate the variety of threats to forest health and efforts to date to protect the resource.
The committee defined forest health as:
A condition that sustains the structure, composition, processes, function, productivity, and resilience of forest ecosystems over time and space.
The panel says that “forest health” is assessed based on current knowledge and is influenced by human needs, cultural values, and land management objectives.
1. A Balanced Analysis
The report does not hype biotechnology for solving problems. The panel called for research on even the foundational question: whether resistance imparted to tree species through a genetic change will be sufficient to persist in trees that are expected to live for decades to centuries as well as in the generations they parent.
The report compares the two approaches to enhancing genetic resistance to pests, i.e., selective (traditional) breeding and relying on biotechnology. Both involve multiple steps, expense, and risks of pursuing what ultimately turn out to be dead ends.
Thus, in traditional selective breeding, scientists must complete the following steps:
1) Determine whether genetic resistance exists within the affected tree species’ population. According to the Academy report, while many tree species have some degree of resistance to particular native or non-native pests, finding suitable parent trees can be difficult, and even when they are found, not all the progeny will be resistant.
2) Evaluate the durability of resistance in order to protect trees over decades.
3) Propagate the resistant progeny in greenhouses or seed orchards to create sufficient resistant genotypes for restoration and reforestation. Many tree species are difficult to propagate using cell culture and regeneration.
In applying biotechnology techniques, scientists must complete the following steps:
1) Identify the genes carrying pertinent traits – which are to be modified, introduced, or silenced. Scientists don’t know what genetic mechanisms underlie important traits. This discovery process is more difficult for tree species than for agronomic crops due to the plants’ large size, long generation time, and (in the case of conifers) immense genomes. Another problem is that forest trees have high levels of heterozygosity due to their large population sizes and outcrossing breeding systems, which complicates genome assembly and modification. Still, recent technological improvements are making this identification process easier.
2) Insert the genes using various biotechnology tools such as transgenesis and genome editing.
3) Produce trees containing the desired gene sequence to regenerate plants from disorganized callus tissue. As noted above, many tree species are difficult to propagate using cell culture and regeneration. Even when this approach is possible, the regeneration of a plant from a single cell may not produce an individual that has the desired genetic change in every cell.
The time line for applying either approach to protect forest health will depend on several factors, including the biology of both the tree and the pest, and the environments in which the target tree species exists. It can vary from a few years to multiple decades.
2. Who Should Carry Out Genetic Improvement of Trees (and by implication, all long-term strategies to protect forest health)?
Trees provide private as well as public benefits, such as income from timber sales. However, the costs of developing a genetically resistant tree – whether achieved through traditional breeding or biotechnology processes – will be incurred up front and the benefits will follow later – often decades or even centuries later. Consequently, the sponsors need a long time horizon!
The panel suggests that the public sector can have greater patience when it perceives that significant public benefits will be forthcoming. The private sector is not likely to invest in the protection of forest health because it cannot fully capture the benefits that may accrue. The authors define “public sector” to include government agencies and non-profit organizations.
Part B. Impacts, Ethics, and Policy
1. Impacts
The report provides careful analysis of the ecological impacts that should be considered in evaluating the use of biotechnology to maintain or improve forest health. The report emphasizes that if the modified trees are to spread and restore the species to its role in the ecosystem, the modified trees must be competitive in the ecosystem (while not being invasive!). The trees must be suited to the variety of climates and other biophysical conditions found throughout the tree species’ range. The report even said that establishing the rangewide patterns of distribution of the target species’ natural standing genetic variation should be researched before a project is begun aimed at inserting pest resistance genes.
2. Public attitudes and ethical considerations
The panel was charged to consider social, cultural, and ethical issues related to the potential use of biotechnology to develop trees resistant to pests. They devote 13 pages to examining this complex set of issues, which range from Native Americans’ use of black ash to concepts of “wildness” and competing models of “conservation”. There have been few surveys or other studies of Americans’ attitudes. The panel also notes that the public lacks in-depth knowledge about genetic interventions and processes, so their attitudes are likely to change — for or against use of the technology — as they learn more or associate biotech with strongly held beliefs.
The Panel notes that important ethical questions fall outside any current “impact analysis” evaluation system, or any new analysis that focuses on “ecosystem services”. It calls for additional research on societal response to biotechnology applied to forest health and development of new forms of engaging full range of stakeholders.
3. Need for a New Impact Assessment Framework
The panel concludes that the current regulatory system does not provide for consideration of most aspects of forest health in assessing the safety of a tree developed through biotechnology, including those described above. Consequently, the panel calls for an entirely new assessment process in order to evaluate both the ecological and social/ethical considerations.
The long-standing Coordinated Framework for the Regulation of Biotechnology relies on existing federal statutes. Under this system, the regulatory agencies (USDA Animal and Plant Health Inspection Service, Environmental Protection Agency, sometimes Food and Drug Administration) regulate specific products, not the process by which the products are produced. For example, USDA regulates only the small subset of biotech trees which were transformed via use of a bacterium, Agrobacterium tumefaciens, to insert the desired trait.
The panel says that an agency undertaking an environmental analysis under the terms of the National Environmental Protection Act would need to add an analysis of some components of forest health.
To rectify these analytical gaps, the panel suggests creation of an integrated impact assessment framework that combines ecological risk assessment with consideration of ecosystem services. This integrated framework would evaluate the effect of the pest threat – and responses to that threat – on forest processes –as well as on associated cultural and spiritual values. The impact assessment must make explicit the links between specific forest protections and their effects on important ecosystem services. The panel points to an EPA guidance document on economic impact analysis (see reference at the end of this blog) as a useful starting point. The panel suggests that this framework should be used to evaluate any forest health intervention, including use of selectively bred trees.
Because of the length of time until tree reproductive maturity and long life span of most trees, collecting data for an impact assessment might take years. The panel suggests adopting a tiered system which would allow field trials of low-risk transgenic trees to reach flowering stage so as to provide data on gene flow and climatic tolerances – data that are essential for a proper impact assessment that would evaluate the likelihood of ultimate success of the restoration effort. Such experiments and carefully developed models must also identify sources of uncertainty.
Adoption of such a stepwise, iterative process requires abandonment of the current regulatory system, which does not permit the flowering of biotech trees in most cases.
My Conclusions
The report makes clear several realities:
1) the magnitude of the threat to our forests from non-native pests – which warrants an effective response;
2) the strengths and weaknesses of the several response strategies – none of which can solve this problem in isolation;
3) the scientific challenges that need to be overcome to apply strategies aimed at enhancing tree species’ genetic resistance to pests;
4) the need for greatly expanded programs to implement the various strategies.
Also, the report shows how unprepared our country is to systematically assess the full impacts of new forms of tree breeding and forest health. To rectify this gap, the report also calls for a complete overhaul of the procedures by which the government currently evaluates the environmental risks associated with applying one of the strategies, genetic transformation of the plant host – which is defined (in the Glosssary) as including transgenesis, cisgenesis, RNA interference, genome editing, and insertion of synthetic DNA.
The recommended actions in this report – taken either individually or collectively – require a level of commitment by government and conservation organizations that far exceeds the current level.
I hope the Academies’ prestige can prompt such commitment. For example, development of a sufficiently robust coalition of groups could re-invigorate our society’s response to the invasive pest threat. The report has received some encouraging attention. It was reported in Nature and Scientific American. About 130 people tuned in live to the launch webinar on January 8th. So far, almost 1,200 people have downloaded the report.
The government shutdown has delayed the sponsoring agencies’ (USDA and EPA) official reactions to the report. It probably curtailed some publicity efforts among all the sponsoring agencies. Also, the report will be only one item in the overflowing inboxes of agency scientists and managers after 35 days on furlough. I hope it won’t be lost, especially with the threat of a second shut-down.
How can those of us in the public who care about our forests ramp up our activity to support these recommendations?
A reminder: Scott Schlarbaum and I addressed the need for a greatly expanded restoration component as part of a comprehensive response to non-native tree-killing pests in our report Fading Forests III, released five years ago. It is available here.
SOURCES
Aukema, J.E., D.G. McCullough, B. Von Holle, A.M. Liebhold, K. Britton, & S.J. Frankel. 2010. Historical Accumulation of Nonindigenous Forest Pests in the Continental United States. Bioscience. December 2010 / Vol. 60 No. 11
National Academies of Sciences, Engineering, and Medicine. 2019. Forest Health and Biotech: Possibilities and Considerations. Washington, DC: The National Academies Press. doi: https://doi.org/10.17226/25221.
U.S. Environmental Protection Agency. 2014. Guidelines for Preparing Economic Analyses. Washington, D.C.