Many of us use the winter to plan for the next season’s restoration and planting projects. In the next 100 years New Jersey’s climate is predicted to change dramatically as the northeast is warming faster than other regions of the country. This point was driven home at the October 5, 2022 New Jersey Invasive Species Strike Team conference where Dr Evelyn Beaury, current postdoc at Princeton University, presented “Seeding Ecosystems of the Future” based on her research done with the Northeast Regional Invasive Species & Climate Change (RISCC) Management Network. In New Jersey, historically unprecedented warming is projected for the 21st century with average annual temperatures increasing by 4.1 °F to 5.7 °F by 2050 (NJDEP, 2020). The question posed is with rising temperatures, altered precipitation patterns, reduced chilling degree days, and an increase in growing degree days how can we help our forest ecosystems adapt and how will species adapt to change?
What is assisted migration?
One proposed adaptation technique is the idea of assisted migration. Assisted migration is human assisted migration of species in response to climate change. Many are familiar with wildlife migration, for example annual spring and fall bird migrations, but you may not realize that plants also migrate. Forest plant species that cannot tolerate warming temperatures are naturally shifting their ranges and migrating north. For example, based on the US Forest Service Climate Change Tree Atlas, New Jersey’s forest habitat is predicted to be more suitable to forests just south of us where Loblolly Pine, Sweetgum, Pitch Pine, Post Oak, and White Oak may be the more abundant species. Red maple, while still abundant, is expected to be less so in the future along with Sugar Maple and Red Oak (NJDEP, 2020).
But the climate is warming faster than many of these species can keep up. In addition, we face threats from invasive species that can readily tolerate shorter, milder winters and longer summers. That’s where assisted migration of species comes in, the idea being, to give a forest a head start on its future climate. Can we help our ecosystems adapt by creating resilient landscapes and choosing species that are predicted to be more tolerant of our future climate?
The term assisted migration is a general term used to describe a wide range of activity from moving a population within its historic species range to moving wildlife to where it has never existed before. One example is in Vermont where foresters are introducing a variety of Red Spruce, chosen for its origins in the mountains of West Virginia, which is where Vermont’s predicted climate is headed. Read about additional case studies in the northeast as well as a detailed review of operational scale forest assisted migration in this Ecosphere journal article and on the Climate Change Response Framework demonstration project website.
Advantages and Disadvantages
The assisted migration concept has been debated for over a decade as there are many challenges and opportunities that could arise (Handler et al., 2018).
A few of the challenges include
• new species could become invasive. The example frequently sited is Black Locust which is native south of New Jersey in the Appalachian region. It became invasive in our region as it is popular in the ornamental trade and thrives in a variety of habitats.
• new species could introduce diseases or pests.
• new species could hybridize with local existing species.
• new species may not have genetically diverse seed sources or enough seed may not exist for species with limited ranges.
• assisted migration may be more expensive than traditional regenerative practices.
Opportunities from assisted migration include
• helping maintain ecosystem function where species are declining.
• helping maintain forest productivity under climate change.
• provenance data is already available for many species which could help managers make decisions about performance of seed sources from outside their area.
• “life boating” a species that is at critical risk.
• ensure that a species occurs in many redundant locations across a range of conditions.
These issues have a practical application for forest restoration projects. Historically when choosing plant species for restoration projects the goal has been to source seed and plants from the local provenance of the native species. But with the climate quickly warming, some local genotypes (the genetic makeup of an organism) may not be adapted to future climate conditions. The question then becomes, for land managers, how do we choose appropriate plants for resilient landscapes, and how do we make management decisions?
Luckily, I don’t have to answer that question because there are many resources we can use to help plan for climate change adaptation. Whew!
One resource is simply using predicted changes in plant hardiness zones to determine what species might be appropriate into the future. The USDA plant hardiness zones are the standard by which we can determine which plants are most likely to thrive at a location. Zones are based on the average annual minimum winter temperature. By 2070, locations in southern New Jersey are predicted to be in zone 8, allowing some southern species that previously could not tolerate our cold winters to thrive.
Another practical tool is the Natural Areas Conservancy Forest Identification and Restoration Selection Tool. This “plant palette” tool for the NY metro area takes you through a dichotomous key to define your forest type and then proposes a restoration plant palette ranked in tiers from highly to less resilient to disturbance and climate change.
Another resource is the Northeast Regional Invasive Species & Climate Change (RISCC) Management Network which aims to reduce the compounding effects of invasive species and climate change. Their “Management Challenges” two-page documents synthesize the current state of knowledge for example, “Nuisance Neo-natives: Guidelines for assessing range shifting species”, and “Gardening with climate smart natives in the Northeast.”
Two resources focused on trees are the USDA Climate Change Tree Atlas and NJ Forest Adapt developed at Rutgers. The Climate Change Tree Atlas can help answer a range of questions concerning current and projected suitable habitat for many tree species in the eastern United States.
NJ Forest Adapt is more specific to New Jersey and provides access to mapped information on the status of New Jersey’s forests, present and future climate and other forest health stressors to aid land managers in adaptation planning.
The Climate Change Resource Center is a web-based, national platform that connects land managers and decision makers with usable science to address climate change in natural resources planning and management. The focus is on forests and other ecosystems, and you can spend hours getting lost among the library of tools. Included are 3 self-paced modules “Responses to Climate Change: What You Need to Know” which gives a brief overview of natural resource adaptation options, resistance, resilience, and transition, and how to incorporate them into planning, as well as providing definitions and descriptions of mitigation and restoration.
References and Additional Reading
Handler, S.; Pike, C.; St. Clair, B.; 2018. Assisted Migration. USDA Forest Service Climate Change Resource Center. www.fs.usda.gov/ccrc/topics/assisted-migration
Lenart, Melanie. May 16, 2019 “The Debate About Assisted Migration.” Climate, Forests and Woodlands eXtension Community of Practice. climate-woodlands.extension.org/the-debate-about-assisted-migration/
New Jersey Department of Environmental Protection. 2020. New Jersey Scientific Report on Climate Change, Version 1.0. (Eds. R. Hill, M.M. Rutkowski, L.A. Lester, H. Genievich, N.A. Procopio). Trenton, NJ. 184 pp. www.nj.gov/dep/climatechange/data.html
Palik, Brian J., Peter W. Clark, Anthony W. D’Amato, Chris Swanston, and Linda Nagel. 2022.“Operationalizing Forest-Assisted Migration in the Context of Climate Change Adaptation: Examples from the Eastern USA.” Ecosphere 13(10): e4260. esajournals.onlinelibrary.wiley.com/doi/full/10.1002/ecs2.4260