Rethinking “locals-only” practice in grassland restoration
McKone, M.J. and Hernández, D.L. (2021), Community-level assisted migration for climate-appropriate prairie restoration. Restoration Ecology, 29: e13416. PDF.
Summary
Climate change threatens the long-term survival of highly fragmented habitats such as native grassland communities. Restoration plantings can contribute to efforts to conserve grassland biodiversity. Past planting practices have focused on the use of local species and genotypes because these are presumably adapted to local conditions. However, climate change is rapidly altering those local conditions, likely causing some local genotypes to be poorly adapted to future climate conditions. Climate change makes this “local-only” practice obsolete and counter-productive for a goal of restoring resilient grassland communities. Additionally, the rapid pace of climate change makes it unlikely that many grassland species can ‘keep up’, a problem that is exacerbated by extensive fragmentation of native habitats. Without assisted migration, or the human-mediated movement of species to warmer margins of their native range, many species are unlikely to persist.
McKone and Hernández (2021) propose that new grassland restoration plantings incorporate assisted migration at the community level including species and genotypes that are viable in the changed climate. “Climate-adjusted provenancing” uses seed both from local and from multiple non-local populations, with non-local seeds sourced from warmer populations. Selecting and sourcing species for climate-appropriate restorations in this manner is possible with minimal additional cost or expertise. Potential risks of assisted migration are offset by the extreme conservation challenge of highly fragmented communities under climate change. Rather than restoring a previous condition, community-level assisted migration aims to restore the natural process that occurred in response to past episodes of more gradual climate change in a continuous landscape.
The most commonly stated argument against assisted migration is that the resulting range expansions could create novel invasive species. However, assisted migration across relatively small distances on the same continent is fundamentally different from the intercontinental introductions that are the source of most harmful invasive species and carries comparatively low risk (e.g., Simberloff et al. 2012).
Take home points
Current practices for habitat restoration that emphasize planting native species from local sources fail to account for the impacts of a changing climate and threaten the resilience of these systems into the future.
It is virtually impossible that climate-appropriate species and genotypes will be able to migrate on their own at the pace of climate change, especially for highly fragmented biodiversity rich habitats such as tallgrass prairie or coastal grasslands.
Although focused on tallgrass prairie in Minnesota, this research is applicable to other fragmented biodiverse communities, especially our coastal sandplain grasslands in the northeastern US.
Management implications
The climate-smart best practice for prairie and other grassland plantings is to include any species that could survive under current and future climate; a radical departure from “local is best.”
Mixtures of local and climate-appropriate seeds could support adaptation to changing climates.
Related papers: Bois et al. 2023; Von Holle & Motzkin 2007
Keywords
Impact Study; sandplain grasslands; invasive plant; Assisted Migration; Climate Smart Restoration