Biotechnology has the potential to help mitigate threats to North American forests from insect pests and pathogens through the introduction of pest-resistant traits. However, it also presents some challenges. The necessary genetic changes to achieve resistance are often not easy to identify and are challenging to implement. Tree genomes are complex, and much remains to be learned about the genetic mechanisms that underlie important traits. Most resistance traits are thought to be polygenic, controlled by many loci, in theory, potentially hundreds, each of which may have small genetic effects and complex epistatic interactions (Boyle et al., 2017). Additionally, unlike the modification of agricultural crops through biotechnology—in which a genetic change is introduced to and propagated in an individual cultivar or variety—genetic changes incorporated into trees for forest health purposes need to be introduced into diverse breeding populations so that tree species can respond to biotic and abiotic stress over time and across their spatial distributions.
Furthermore, the effectiveness of biotechnology at mitigating forest threats needs to be assessed on many fronts. In addition to evaluating the utility of the resistance trait in protecting a tree species, the modified tree needs to be tested for viability in the diversity of environments in which it will live. An assessment of the effects of the tree on other species in the environment (including humans) is also important, as is a comparison of using biotechnology to address the threat versus using other mitigation tools.
Finally, research and investment efforts need to be made in areas besides biotechnology, including the development of further strategies for preventing the introduction of nonnative insects and pathogens, human capital development in professions related to tree breeding, and social science research, including on a conceptual framework for capturing and accounting for the intrinsic value of forests. Such work will benefit the health of forests, regardless of the pest mitigation tools put to use.
Therefore, the committee recommends research and investment on three fronts to address knowledge gaps about the application of biotechnology to mitigate threats to forest health and to improve its utility as a forest health tool:
- Knowledge about tree genetics related to resistance,
- Data and tools for impact assessment, and
- Management approaches that take into account disciplines beyond biotechnology.
The recommendations from the chapters are restated here along with a few additional recommendations to support a holistic effort to improve forest health.
Technical constraints and lack of basic information (Scheben and Edwards, 2017) may provide significant challenges to fully utilizing biotechnology in many tree species in the near future. Understanding of the genomes of North American tree species is inadequate given the number of species under threat, insufficient knowledge exists about the fundamental mechanisms involved in resistance to pests to efficiently identify genomic means to mitigate pest damage, and the combination of genes that respond to pest outbreaks is poorly understood in most forest tree species. A thorough knowledge of tree genomes would provide access to a suite of technologies that could contribute to forest health initiatives, such as gene discovery, gene expression profiling, and genome editing.
Once the mechanisms of resistance are understood, researchers will need to ensure that modified trees include the genetic diversity necessary for survival over long generation times in diverse and changing environmental conditions. Biotechnology could be used in combination with selective-breeding programs for tree species at risk to ensure that sufficient genetic diversity is retained in the resistant trees. Biotechnology tools (e.g., transgenesis or genome editing) would be used to insert one or more resistance genes into relatively few tree genotypes, and these trees would become the parent trees in a seed orchard from which resistant seed could be produced. This process is similar to that of selective-resistance breeding, where a finite number of parent trees with documented genetic resistance are placed into seed orchards to produce the seed required for restoration or reforestation goals.
A limitation of selective breeding is the time it can take to combine different resistance genes or to deliver a high percentage of orchard seed that will produce resistant seedlings. For some tree species (e.g., sugar pine, Pinus lambertiana), it may take 10 to 20 years to breed trees with different combinations of resistance genes. Biotechnological tools may be able to combine resistance genes in a much shorter period of time or to combine resistance genes not found in the tree species of interest with resistance genes that are already present in the species. The combination of precision phenotyping to identify trees in the field that express pest resistance, selective breeding, and biotechnological methods could be synergistic in speeding up tree improvement efforts while still ensuring success in the long term. A combined approach may be particularly advantageous when stacking qualitative (notably single-gene) resistance with quantitatively inherited resistance. Seed orchards containing parent trees with qualitative and quantitative resistance (either in the same individual or in different individuals), would produce seed that has qualitative resistance and a varied mix of quantitative resistance.
To address forest health, genetic resistance in trees needs to be durable over hundreds of years. Populations of trees with several types of resistance, including a mix of qualitative and quantitative resistance, would have the best chance of meeting this durability goal. Sustaining forest tree populations over the long term will also require combining durable resistance with a diverse array of genetic backgrounds locally adapted to their microgeographic environments. Provenance tests, ecological niche modeling, and precision phenotyping across multiple ecological niches will shed light on the extent of the locally adapted standing genetic variation present along the wide geographical distribution of a species. Understanding the relationship of spatial distributions, genetic diversity, and local adaptation is essential for determining the genetic backgrounds against which
to deploy a biotech tree to ensure that the breeding program is capturing the maximum possible genetic variation within the species of interest.
Identifying resistance in selectively bred trees usually includes both a relatively fast seedling assay (e.g., artificial inoculation of young seedlings with spores of the pathogen that causes white pine blister rust and evaluation/phenotyping of thousands of seedlings for resistance) and extensive field testing to examine the efficacy of genetic resistance in a range of environments and over time. Any biotechnological resistance introduced in one or more individuals would need to go through one or both of these steps. At the time the committee was writing its report, regulation of field trials of biotech forest trees restricted flowering to guard against unintended gene flow. Caution may be warranted on a case-by-case basis because of the risk of spread of biotech forest trees prior to completion of the initial impact assessment (intended to be informed by field trials). Additionally, modeling and other approaches should be developed to address questions of gene flow, dispersal, long-term performance of resistance in biotech forest trees, and the establishment of and interactions of these trees with other components of the environment.
- Sufficient investment of time and resources should be made to successfully identify or introduce resistance into tree species threatened by insects and pathogens.
- More research should be conducted on the fundamental mechanisms involved in trees’ resistance to pests and adaptation to diverse environments under a changing climate.
- The deployment of any biotechnological solution with the goal of preserving forest health should be preceded by developing a reasonable understanding in the target species of (a) rangewide patterns of distribution of standing genetic variation including in the putative glacial refugia, if known; (b) magnitude of local adaptation (gene × environment relationships); and (c) identification of spatial regions that are vulnerable to genetic offset.
- Entities concerned about forest health should devote resources to identifying resistant trees within a population that have survived a pest outbreak. Research to understand the role of resistance in coevolved systems from the perspective of a global host–pest system, where the nonnative pathogen or insect originate, would help guide efforts in North America.
- Research should address 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 progenitors of future generations.
The timely development of an impact assessment framework is critical. Developing the process for incorporating the risk of ecosystem service loss, including cultural, aesthetic, and nonuse values, and comparing that risk with alternative approaches to address pest threats to tree species will require substantial effort. As more is learned about impacts (positive and negative) of different interventions for forest health over time, the approach can be adaptively modified.
The longevity of trees and the large spatial scales involved in mitigating threats to tree species from pests means that predictive modeling will be needed to evaluate the potential success of using biotechnology to confer pest resistance and to design the outplanting approach to best facilitate gene flow. Uncertainty analysis of model parameters will direct specific research and indicate monitoring needs. While model parameterization will vary by species, geography, and the traits under consid-
eration, development of criteria for these models should be an early research focus. Evaluation of some elements of the impact assessment will only be possible via modeling.
Incorporation of climate change scenarios into modeling efforts would improve the design for species restoration efforts by explicitly representing uncertainty about the suitability of habitats in the future. It would be useful to model climate change scenarios whether resistant trees to be planted are developed using biotechnology or selective breeding. Climate change will influence both pest and tree distributions and pest impacts. Research will be needed to refine these predictions by species over time.
Furthermore, if the decision is made to go ahead with outplanting a biotech tree, a full monitoring and assessment plan should be developed so that ample learning takes place from these initial efforts. The knowledge gained can then be used to adaptively refine both the decision-making approach and the impact framework. For example, field testing of seedlings should reveal both the movement and durability of resistant genes through a tree population. These data will help with evaluation of whether the next generations of the species will propagate resistance through natural regeneration as intended and whether other traits have been modified with the addition of resistance. Where flowering trials are permitted, results would inform both impact assessment and modeling to predict the consequences of large-scale deployment. Focused research and tracking of early biotech species should improve decision making about other species under consideration for biotechnological solutions. Adaptive management that facilitates a stepwise approach to data gathering on gene flow and other impacts at different spatial and temporal scales would be useful for achieving the goal of addressing forest health.
Forest health is not currently considered in the federal regulatory assessments of approaches to mitigate forest health threats, whether or not those approaches use biotechnology. The committee was not tasked with suggesting changes to the U.S. regulatory system, but it thinks that the regulatory agencies of biotech plants—particularly the U.S. Department of Agriculture and the U.S. Environmental Protection Agency—could explore whether an assessment of impacts on ecosystem services could be incorporated into their oversight responsibilities. Such assessments should be done for all approaches designed to address forest health, not just biotechnology.
- Federal agencies should continue efforts to improve the incorporation of all components of ecosystem services into the integrated impact assessment.
- Modeling and other approaches should be developed to address questions about biotech tree gene flow, dispersal, establishment, performance, and impact that are precluded where flowering of field trial material is restricted.
- Models for tree biotech impact assessments should identify, quantify, and account for sources of uncertainty.
- An adaptive management approach to forest health should be used to ensure continued learning and address impacts to both the environment and society.
- Impact assessment should be a continuous and iterative process.
- Regulatory agencies should explore ways to incorporate into their regulatory oversight responsibilities the ability to assess the impact on ecosystem services for biotech and non-biotech products developed for improving forest health.
Biotechnology is one of many approaches to addressing forest health and should not be pursued to the exclusion of other forest health management options, including prevention and site manage-
ment practices. Substantial literature supports the need for sustained investment in prevention and eradication as the most cost-effective and lowest impact approaches for managing introductions of nonnative insect pests and pathogens. Where these efforts fail or when native pests and pathogens are involved, multiple management options may be needed. Many responses will likely require integrated approaches for positive impact. Amplifying existing or introduced genetic resistance of the host species through breeding is an essential element for mitigating the impacts of introduced pathogens or insects. Several ongoing breeding programs reviewed in Chapter 3 give reason for optimism about the feasibility of this approach, and new technologies may increase their efficiency in the future. All management approaches will require sustained resources because eradication of widespread infestations has low probability, insect pests and pathogens can evolve over time, reintroduction of insect pests and pathogens is likely, and some options require decades for successful development and deployment. Continuing efforts to track the import of new pests, the spread of existing native and nonnative pests, and the potential evolution of pests in response to both increased resistance and other drivers will also be necessary to ensure that any management effort is consistent with the current and expected threat.
To be used successfully as a tool for mitigating forest health threats, biotechnology needs to be integrated into selective-breeding programs to capture existing genetic diversity. However, many forest tree species under severe pest attack do not have adequate and sustained breeding programs. Furthermore, the capacity of selective-breeding programs in U.S. institutions has been severely eroded since the mid-20th century (Wheeler et al., 2015). Human capital will be needed in the professions of tree breeding genetics, computational biology, forest pathology and entomology, tree physiology, invasion biology, biogeography, forest economics, and rural sociology to guide the effective development and potential deployment of pest-resistant trees. Research training is available in most of these disciplines at many public institutions, but they seldom operate under a cohesive theme. To train future scientists with the expertise needed to address forest health threats, institutions may want to consider undertaking cluster hires of faculty from each of these disciplines to foster collaborative multidisciplinary research in these areas. They could also create multidisciplinary graduate programs to provide professional training in two or more of these disciplines. Furthermore, many biologists still receive little training in computational science. Making such training part of graduate programs in forest-related disciplines will go a long way toward development of strong quantitative skills in professionals dealing with large datasets (Spengler, 2000).
Interventions to address forest health using biotechnology should be evaluated not only as a matter of technical feasibility but also as relevant to social values. The impact assessment framework as proposed in Chapter 5 aims to reflect this inclusive approach, but there are challenges to the adequacy of its treatment of these considerations. Recent research on public attitudes in a variety of countries, although currently very limited, suggests some openness to using biotechnology to alter trees. However, ongoing controversy over the use of biotechnology in agricultural crops demonstrates that significant concerns exist among segments of society. Accordingly, these views should be recognized as important parts of the public dialogue about the potential for the use of biotechnology to address forest health.
Forests, especially noncommercial ones, are often associated with values such as naturalness, wildness, integrity, authenticity, sense of place, and place bonding, and they provide critical habitat for intrinsically valued and iconic species such as northern spotted owls. Biotechnological interventions may, on the one hand, be regarded as potentially undermining values such as naturalness, wildness, or integrity in forests and may also tap into more basic and unacknowledged disapproval of the management of forests (Hall, 2007; Gamborg and Sandøe, 2010). Alternatively, such interventions may be perceived as offering hope to preserve threatened species, much loved and culturally significant places, and valued ecosystems from the substantial changes that could follow the loss of a foundation species such as the whitebark pine.
The lack of clarity about how such values are likely to be interpreted and prioritized in the context of biotechnological interventions into forest health means that more studies of societal responses are needed. Studies should investigate how different cultural groups are likely to respond to the deployment of biotechnology for forest health, how stable and consistent these responses are, how they are related to deeper value orientations, and how they are affected by changes in knowledge about the technology. Whether some biotechnological strategies are generally thought more acceptable than others (for instance, whether cisgenesis is more acceptable than transgenesis, or whether genome editing is more acceptable where it does not involve transgenesis) and how people think about trade-offs between environmental values, such as the loss of some wildness value to protect an endangered species, should also be investigated.
Biotechnical interventions for forest health are likely to impose varying risks, costs, and benefits on different human groups over time, particularly on indigenous peoples. Where the development and deployment of biotech trees is being considered, these social impacts should be investigated, research into the perspectives of individuals and communities likely to be affected should be carried out, and affected communities should be engaged transparently and respectfully.
To take these concerns meaningfully into account, a conceptual framework is needed to complement impact assessment based on ecosystem services. This framework should take into account the ways that forests are valued intrinsically, spiritual and ethical concerns about the impacts of biotechnology on forests, and concerns about social justice related both to the impacts of biotech trees on diverse communities and the involvement of these communities in decision-making processes.
Visions of informed decision making and democratic governance associated with forest health threats and emerging technologies must go well beyond just educating people with scientific facts. Instead, policy makers must gain trust and connect with the different beliefs, values, and priorities that various groups of people hold (Brossard and Nisbet, 2006; Hajjar and Kozak, 2015). Spaces need to be created to initiate meaningful dialogue where diverse viewpoints and values can be brought together, concerns and past hardships can be expressed, and perceptions can be understood (Kleinman et al., 2011; Hajjar et al., 2014). One strategy for fostering this meaningful deliberation is to discuss risks in connection with benefits, although these issues are challenging to measure and represent in quantitative impact assessments or as part of models measuring various ecosystem services. Other approaches that respect and integrate local knowledge and mesh with local cultures of decision making may also hold promise. Regardless of the method, for engagement to matter, policy makers and technical experts must be open to reconsidering and possibly modifying their understandings and plans for action.
- Investment in effective prevention and eradication approaches should be the first line of defense against nonnative species in efforts to maintain forest health.
- Management for forest health should make use of multiple practices in combination to combat threats to forest health.
- Public funders should support and expand breeding programs to encompass the genetic diversity needed to preserve tree species essential to ecosystem services.
- Investment in human capital should be made in many professions, including tree breeding, forest ecology, and rural sociology, to guide the development and potential deployment of pest-resistant trees.
- More studies of societal responses to the use of biotechnology to address forest health threats in the United States are needed. Such studies might investigate (1) the responses of different social and cultural groups to the deployment of biotechnology in forests, (2) the stability and consistency of attitudes toward different applications
- of biotechnology in a range of circumstances, (3) differences in attitudes toward biotechnology strategies (e.g., cisgenesis, transgenesis, genome editing), (4) the relationship between deeper value orientations and attitudes toward biotechnology, and (5) how people consider trade-offs between values such as wildness and species protection.
- Studies of societal responses to the use of biotechnology to address forest health threats should be used to help in developing a complementary framework to ecosystem services that takes into account intrinsic values, related spiritual and ethical concerns, and social justice issues raised by the deployment of biotechnology in forests.
- Respectful, deliberative, transparent, and inclusive processes of engaging with people should be developed and deployed, both to increase understanding of forest health threats and to uncover complex public responses to any potential interventions, including those involving biotechnology. These processes, which may include surveys, focus groups, town hall meetings, science cafés, and other methods, should contribute to decision making that respects diverse sources of knowledge, values, and perspectives.
- Developers, regulators, and funders should experiment with analytical-deliberative methods that engage stakeholders, communities, and publics.
Boyle, E.A., Y.I. Li, and J.K. Pritchard. 2017. An expanded view of complex traits: From polygenic to omnigenic. Cell 169(7):1177–1186.
Brossard, D., and M.C. Nisbet. 2006. Deference to scientific authority among a low information public: Understanding U.S. opinion on agricultural biotechnology. International Journal of Public Opinion Research 19(1):24–52.
Gamborg, C., and P. Sandøe. 2010. Ethical considerations regarding genetically modified trees. Pp. 163-175 in Forests and Genetically Modified Trees, Y.A. El-Kassaby and J.A. Prado, eds. Rome, Italy: Food and Agriculture Organization of the United Nations.
Hajjar, R., and R.A. Kozak. 2015. Exploring public perceptions of forest adaptation strategies in Western Canada: Implications for policy-makers. Forest Policy and Economics 61:59–69.
Hajjar, R., E. McGuigan, M. Moshofsky, and R.A. Kozak. 2014. Opinions on strategies for forest adaptation to future climate conditions in western Canada: Surveys of the general public and leaders of forest-dependent communities. Canadian Journal of Forest Research 44(12):1525–1533.
Hall, C. 2007. GM technology in forestry: Lessons from the GM food “debate.” International Journal of Biotechnology 9(5):436–447.
Kleinman, D.L., J.A. Delborne, and A.A. Anderson. 2011. Engaging citizens: The high cost of citizen participation in high technology. Public Understanding of Science 20(2):221–240.
Scheben, A., and D. Edward. 2017. Genome editors take on crops. Science 355(6330):1122–1123.
Spengler, S.J. 2000. Bioinformatics in the information age. Science 287(5456):1221–1223.
Wheeler, N.C., K.C. Steiner, S.E. Schlarbaum, and D.B. Neale. 2015. The evolution of forest genetics and tree improvement research in the United States. Journal of Forestry 113(5):500–510.