CHAMPAIGN, Ill. — A study analyzing the effects of climate change on vascular plants in the United States finds that the fate of individual plant species tends to be a regional phenomenon.
A plant species found in the Southwest U.S., for example, may be more vulnerable to climate change than the same species in the Midwest, or vice versa, the study found. This showed that focusing on regional rather than national data yielded the most reliable results for understanding which species are most in need of conservation, and where, the researchers said.
The findings are reported in the journal Ecography.
The regional zones used in the study were delineated more than a decade ago by the U.S. Geological Survey National and Regional Climate Adaptation Science Centers , a multi-institutional project initiated by the U.S. Department of the Interior to "protect the country's natural and cultural resources from the dramatic effects of climate change." The study included seven CASC regional zones : Midwest, North Central, Northeast, Northwest, South Central, Southeast and Southwest. Each of these regions in the contiguous U.S. includes between three and 14 states and is defined by state boundaries.
"The CASC Network is an already well-established system of partnerships and management structures designed to help wildlife adapt to climate change," said Weiqing Qu, a Ph.D. student in the School of Integrative Biology at the University of Illinois Urbana-Champaign who led the new research. She and her colleagues at Illinois chose to focus on vascular plants because they are "taxonomically, functionally and genetically diverse, and very sensitive to climate change," she said. They also are well documented across the lower 48 states, making it easy to collect and analyze their abundance in different regions.
The researchers wanted to determine how to best evaluate plant vulnerability to climate change using the available data, Qu said.
"All we need for this method is two data sets: plant geographic occurrence records and climate niche breadth," she said. "The underlying assumption is that if a plant occupies a broader climate niche, it may be less sensitive to climate change."
For example, plants found across a wide range of elevations or latitudes may experience a broader range of climatic conditions, potentially making them less sensitive to climate change, Qu said. In regions with diverse elevations, cooler areas may provide potential refuges for some plant species as temperatures rise.
The team used these data sources to calculate the "intrinsic climate sensitivity" of each plant species analyzed. The study included 384 species found in each of the seven CASC regions, and 22 species that occur in every one of the 48 states that make up the CASC regions.
After determining species' climate sensitivity in different states or regions, the team compared those values, finding that each species' climate sensitivity tended to be more similar within a CASC region than across regions. They also found that plants that occupy a broader swath of territory in regions with a lot of geographic diversity or in areas with a glacial history tend to be less vulnerable to climate change.
These differences may reflect their evolutionary and biogeographic histories, Qu said. Historical glacial activity or landscape diversity may have influenced how plants dispersed, recolonized different regions and occupied a range of environmental conditions. Such processes could help explain why the same species exhibits different levels of climate sensitivity across geographic regions.
The researchers compared their intrinsic climate sensitivity rankings with state conservation status rankings, another method used to evaluate threats to plant persistence. Their findings largely paralleled the state rankings while streamlining the process.
State conservation status rankings are a useful tool for determining which species are of most concern for conservation. These rankings dovetail with national and international rankings of extinct, endangered, rare or threatened species and are used in those assessments.
But state and national conservation rankings rely on a more time-consuming process of evaluating a variety of factors that may influence a plant's status. This sometimes leads to gaps in the data, Qu said.
For example, some states, including Illinois, use a protocol developed by NatureServe , a source of biodiversity data that, according to its website, "works with 60 network organizations and nearly 1,000 conservation professionals to collect, analyze and deliver biodiversity knowledge that informs conservation action." NatureServe's process for plants involves analyzing each species' widest distribution, population size, number of occurrences, short-term and long-term trends and known threats.
The data is reliable and trusted by conservationists, but some plants in some states have not been ranked, Qu said.
"With our method, we can fill in the missing data," she said. "This approach is also useful for seeing how individual species' climate sensitivity varies across regions and which environmental factors are associated with those differences.
"Previously, we put a lot of emphasis on how different species respond to climate change, but in this study, we're focusing on whether the same species shows different levels of climate sensitivity across different regions," she said. "We are emphasizing that a one-size-fits-all strategy doesn't work. Understanding these regional differences can help practitioners direct conservation resources to where they are most needed." And to do that, "we need to have a region-specific conservation strategy."
The U.S. Environmental Protection Agency supported this research.
Jason Bried , a research scientist in the School of Integrative Biology and in the Illinois Natural History Survey at the U. of I., co-led the research with Qu. The INHS is a division of the Prairie Research Institute at Illinois.
