Impacts on New England Plants
Rapid warming, more intense storms, and drought will change plant communities
The 2018 Fourth National Climate Assessment predicts that rising temperatures and altered patterns of precipitation will lead to significant changes in New England's plant communities and to further loss of habitat from the coasts to the mountaintops.
To enhance the ability of plants and plant communities to adapt to a changing climate, we need to start by reducing, mitigating, or reversing the damage caused by human activities and infrastructure. Helping to improve the resiliency of vulnerable places is also a crucial step. Our seed-collecting work in the wake of Hurricane Sandy has assisted coastal communities throughout New England to restore healthy, functioning habitats. Other important actions include:
- Protecting as much intact, diverse, complex habitat as possible
- Increasing connectivity between natural areas to facilitate migration
- Monitoring rare plant populations and exemplary habitat for health and threats
- Collecting and banking seeds of rare species and common species to preserve genetic variation
- Managing habitats and removing invasive species where necessary and feasible
- Augmenting or reintroducing rare plant populations within the historic range as needed
- Performing managed relocation of rare plants if necessary
So what will happen to New England's plants? The short answer is that with decreasing seasonality, more drought, and increasing heavy rainfall events, some will adapt, some will migrate, and some will be lost.
Winners and Losers
This is not the first change in climate for a region with rocks dating back a billion years.
New England has experienced long periods of glaciation, warming, and cooling, during which waves of plants colonized, retreated, and remixed. With the climate changing rapidly—in decades rather than millennia—the only certainty is that plant communities will change as well.
Plants adapt to environmental stress by altering their metabolism, flowering, growth, and reproduction; and by migrating toward areas with more favorable climatic conditions. It is difficult to predict the impact of climate change on individual species, which have different capacities to adapt or migrate. Thus most models focus on the vulnerability of habitats.
The scientific consensus is that our alpine, freshwater aquatic, and some forest habitats are most at risk. We're already seeing some encroachment of trees into the alpine tundra, and are expecting the montane spruce-fir forest in parts of New England to disappear. There will a reduction in aspen-birch forests, and maple-beech-birch forests may be completely displaced by more southern oak-hickory and oak-pine forests by the end of the century (one of the winners).
The effect on aquatic systems will vary. Coastal marshes are threatened by sea-level rise. Our iconic boreal wetlands—bogs, fens, and peatlands—are at risk from increased temperatures and more frequent drought, which will dry the substrate and accelerate the decay process. That will promote tree growth and succession to forest. One study in Maine predicts that 85 percent of rare riparian species, 95 percent of open water species, and 83 percent of estuarine marsh species will be lost.
It's a sobering picture, but to a large extent, we have to let nature run its course. We can help maintain functioning ecosystems—whatever the mix of plant species—by lessening the myriad threats our own activities and newly arriving invasive species pose to the plants that define our home.
Relocate Plants, or Not?
With natural systems in flux, scientists want to protect biological diversity and avert extinctions.
The fast pace of climate change is likely to outstrip the speed at which some plants can evolve to tolerate new conditions, and the barriers we have constructed on the landscape over the last 400 years will limit plants' ability to migrate. Conservation strategies like seed banking and land protection are not controversial. But there is considerable debate about more direct intervention, such as managed relocation, which is moving plant species outside their current historic range; and managed evolution, which is modifying the genetic properties of plant populations by introducing genes from another population growing in different conditions.
Native Plant Trust and its partners in the New England Plant Conservation Program have developed preliminary guidelines on managed relocation. First, it is premature to relocate rare or small-range species that are not declining in the wild due to climate change. Second, targets for further research related to relocation are rare, endemic plants in habitats considered vulnerable to climate change. We identified a dozen taxa as potential candidates for relocation.
Finally, we would like to note that it is not necessary to move common species into New England from other regions, and it is premature to use more southern species rather than New England native species in landscaping and restoration projects. Scientists continue to study the climate tolerances of plant species and genetic modifications. Until we know more, we should be cautious about intervening in nature's own climate adaptations.
Prepare for New Invasive Plants
Kudzu (Pueraria montana), known as "the vine that ate the South," is already present in Connecticut and Massachusetts. What comes next?
Two local scientists, Jessica M. Allen at the University of New Hampshire and Bethany A. Bradley at the University of Massachusetts, modeled the likely impact of climate change on the spread of invasive species already present in the U.S. Their analysis, published in peer-reviewed journals and in our magazine, identifies 140 species likely to find a suitable climate in one or more New England states by 2050. They will not all take root here, but we can expect to see some of the invasive species now growing in southern and western states to move in. For example, turnipweed (Rapistrum rugosum) and sawtooth oak (Quercus acutissima) are poised to expand into this region. We also need to pay attention to vulnerable places: as they warm, higher-latitude and mountainous areas, which are now somewhat protected by their cooler temperatures, are expected to gain invasive plant species.
What can we do? The region's botanists and ecologists can combine our collective knowledge about the habitat, soil, and climate preferences of individual invasive species with models of climate shifts to develop a watch list. Allen and Bradley are also developing impact assessments for all invasive plants likely to expand into New England, which will help us set priorities for early detection, eradication, and management.
Stay Informed to Keep Resilient
Two recent reports analyze how climate change is affecting the region, the nation, and the world
With information comes the opportunity to increase resiliency and reduce risk. These documents include not only frightening predictions of peril caused by a warming climate, but also exemplary adaptation strategies from the community level to the global scale.
Impacts, Risks, and Adaptation in the United States: Fourth National Climate Assessment, Volume II, 2018. Published by the U.S. Global Change Research Program, the volume includes chapters on how climate change is affecting each region of the country. Chapter 18 discusses the Northeast.
Special Report on Global Warming of 1.5°C, October 2018. This Special Report by the Intergovernmental Panel on Climate Change "examines the impacts of global warming of 1.5°C above preindustrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty." It is the first publication in the Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report (AR6).