Operationalizing forest‐assisted migration in the context of climate change adaptation: Examples from the eastern USA

Abstract

There is increasing momentum to implement conservation and management approaches that adapt forests to climate change so as to sustain ecosystem functions. These range from actions designed to increase the resistance of current composition and structure to negative impacts to those designed to transition forests to substantially different characteristics. A component of many adaptation approaches will likely include assisted migration of future climate-adapted tree species or genotypes. While forest-assisted migration (FAM) has been discussed conceptually and examined experimentally for almost a decade, operationalizing FAM (i.e., routine use in forest conservation and management projects) lags behind the acceptance of the need for climate adaptation. As the vulnerability of forest ecosystems in climate change increases, FAM may need to become an integral management tool to reduce long-term risks to ecosystem function, despite real and perceived barriers for its implementation. Here we discuss the concept of operational-scale FAM and why it remains a controversial, not yet widely adopted component of climate adaptation. We present three case studies of operational-scale FAM to illustrate how the practice can be approached pragmatically within an adaptation framework despite the barriers to acceptance. Finally, we discuss a path toward advancing the wide use of operational-scale FAM.

Seedbed not rescue effect buffer the role of extreme precipitation on temperate forest regeneration

“…Subsequently, this relationship is again modified by seed functional traits whereby differences in seedling survival are unaffected under mesic moisture regimes, but profoundly reduced for species with smaller seed masses relative to nursery transplants. These results are important when considered in the context of natural recruitment dynamics of forests under climate change relative to recent efforts to plant seedlings to enhance forest carbon stocks (e.g., reforestation, afforestation; Domke et al, 2020) or adapt species to shifting ranges (e.g., assisted migration; Clark et al, 2021;Palik et al, 2022). By testing sown seeds (analogous to natural regeneration), our results showed that future precipitation regimes may filter the germination and survival response for certain species (and traits), although these differences are less apparent for planted nursery stock.…”

Adaptive potential and genomic vulnerability of keystone forest tree species to climate change: a case study in Scots pine

“…The scarcity of studies reporting very high selection coe cients (s > 0.5) suggests that the time required for allele frequency changes may need to be long 8 . Thus it is evident, that standing genetic variation in many places may become maladapted to rapidly changing environments and alternative approaches as compared to natural regeneration might be needed to ensure the resilience of Scots pine in the face of climate change 7,40,105 .…”

“…Before any FAM implementation, empirical validation of the robustness of genomic prediction, such as through common garden experiments, seems to be of critical importance 111 . Subsequently, careful selection of the potential source population for assisted migration suited for each location and adequate policy adjustments are needed 105 . Especially challenging, given the vast range of Scots pine, are the existing regulations regarding the maintenance of seed zones and transfer of reforestation material in different countries.…”

“…Despite the challenges, it seems that assisted climateadaptive strategies must be considered soon, as lack of action will likely lead to signi cant losses, both ecologically and economically. Successful implementations of various assisted migration approaches in other forest tree species like black ash, red pine, and eastern white pine (Palik et al 2022) and their frameworks could serve as valuable guidelines for developing solutions suited for Scots pine and could help mitigate those costs [114][115][116] . Genetic diversity on a regional scale in Scots pine.…”

Comparing assisted migration seed sources of two oak species in a Minnesota red pine woodland

“…This is termed forest assisted migration, hereafter FAM, to distinguish it from species rescue assisted migration, which may be done to bolster populations of a threatened species and not necessarily in response to climate change (Pedlar et al 2012). For FAM to become an operational practice, such that its use is a routine part of forest management at the spatial scale characteristic of an organization (Palik et al 2022), adequate numbers of desired seedlings need to be available for planting.…”