Not seeing future forests for lack of trees
Clark, P. W., D'Amato, A. W., Palik, B. J., Woodall, C. W., Dubuque, P. A., Edge, G. J., ... & Zimmerman, C. L. (2023). A lack of ecological diversity in forest nurseries limits the achievement of tree-planting objectives in response to global change. BioScience, 73(8), 575-586. PDF
Written by Bethany Bradley, edited by Audrey Barker-Plotkin
Summary
In the Northeast, trees are a critical component of most ecosystems and restoration projects often involve small- to large-scale tree plantings. Climate-smart reforestation assists the northward movement of species that might otherwise not ‘keep up’ with the rapid pace of climate change, a practice that could also increase the resilience of forest communities to climate change. Unfortunately, Clark et al. (2023) highlight low quantity and diversity of nursery-grown tree seedlings as major barriers to climate-smart forest restoration. First, there aren’t enough seedlings to plant. Seedling production (and its associated infrastructure) will need to more than double to keep up with U.S. tree planting goals. Second, seedlings that are produced have limited species diversity. Most cultivated tree species meet the goals of foresters and landscapers rather than restoration professionals, leading to a lot of focus on a handful of species. As an example, Clark et al. (2023) note that in 2022 only 800 seedlings of red spruce (Picea rubens) were available - barely enough to restore a single hectare. Third, growers keep poor records of seed provenance. Lack of information about the source population hinders our ability to restore with warm-adapted genotypes. Moreover, where Clark et al. (2023) were able to find information about seed provenance, the geography of collections was very narrow - we may be creating genetic bottlenecks in our seedlings that will reduce the capacity of restored forests to adapt to climate change. Finally, very few seedlings are grown in the Northeast states and those that are are concentrated in Pennsylvania and Maryland. While these genotypes are probably a good choice for New England states (if they are sourced locally in PA and MD), growing them further south can be problematic because the logistics of transport and the likelihood of cold shocks during planting can lower seedling success. To overcome these barriers, Federal and State agencies need to take the lead. Key actions include updating policies for moving species and genotypes to be responsive to climate change, investing in extension professionals to coordinate among foresters, nursery professionals, and restoration ecologists, and making substantial investments in public nursery infrastructure.
Take home points
Lack of tree seedling production for a diverse array of species hampers our ability to direct forests towards greater climate resilience
Lack of accessible information about seed provenance makes it harder to select for warm-adapted genotypes
Management implications
Greater investment in growing trees for restoration now will pay off in the future
Talking with commercial seedling producers about restoration needs could incentivize some private growers to add more species that support restoration
Federal and state agencies need to invest in nursery infrastructure
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