Black ash forest in Minnesota.
Hardwood forests, like this one in Minnesota, would be reclassified from vulnerable to endangered if climate vulnerability were factored into the ecosystem’s risk factor. Credit: Eli Sagor, CC BY-NC 2.0

Ecosystems play a vital role in maintaining biodiversity and provide such services as water and air filtration, pollination, and erosion prevention. But globally, ecosystems are being degraded by such human impacts as land development and pollution.

“Climatic changes will impact the structure, composition, and functioning of ecosystems. So it’s a good idea to include climate risk in the assessment to effectively conserve and manage ecosystems.”

To assess the status of ecosystems and guide conservation policies, the International Union for Conservation of Nature (IUCN) established the Red List of Ecosystems (RLE) in 2014. Ecosystems are evaluated and categorized with terms borrowed from IUCN’s internationally recognized categories for endangered species: from least concern (the least severe) to collapsed (the most severe, akin to extinction).

Risk factors used for RLE assessment include rates of spatial decline, rates of abiotic degradation (such as erosion), and rates of disruption to biotic processes (such as epidemics).

Now a study conducted by scientists from the U.S. Forest Service and NatureServe, a nonprofit organization working on wildlife conservation, factors in climate change vulnerability as a risk factor for the RLE.

“It’s a good idea to include climate risk in the assessment to effectively conserve and manage ecosystems,” said Mahesh Sankaran, a professor of ecology at the National Centre for Biological Sciences in Bangalore, India, who was not involved in the study, because “climatic changes will impact the structure, composition, and functioning of ecosystems.”

Developing a Vulnerability Index

Researchers first developed a framework called the Habitat Climate Change Vulnerability Index (HCCVI). The index considered such factors as exposure (the extent to which the climate within an ecosystem is likely to change), sensitivity (the degree to which any ecosystem is likely to be affected by these changes), and resilience (the ability of the system to recover).

Patrick Comer, chief ecologist at NatureServe and lead author of the new paper, said, “One needs to think about climate vulnerability differently for an ecosystem than an individual species, as we’re dealing with an assemblage of species in their environment and how they interact. That was our intent with this framework.”

The authors applied the index to 33 ecosystems in 10 discrete categories in the United States, ranging from cool temperate subalpine woodlands (the Rocky Mountains) to warm temperate grasslands (tallgrass and shortgrass prairies in the Midwest).

“The intent is to assess climate vulnerability of major habitats that people manage and help them think about appropriate adaptation responses.”

They characterized a climate baseline for each ecosystem type (category) using observed climate data from 1976 through 2005. Exposure measures were calculated on the basis of changes in 19 bioclimatic variables such as annual mean temperature, annual precipitation, and seasonal mean climate conditions. Measures of ecosystem resilience included landscape condition, the presence and activity of invasive species, and the vulnerability of keystone species.

When the authors applied the HCCVI to the RLE, they found that 17 of the 33 ecosystem scores shifted to higher-risk categories, including endangered.

NatureServe is currently helping various federal agencies in the United States, including the U.S. Fish and Wildlife Service and the Bureau of Land Management, to apply the HCCVI to land management practices.

“The intent is to assess climate vulnerability of major habitats that people manage and help them think about appropriate adaptation responses. However, we’re still in early stages in terms of the actual application,” Comer added.

Local Ecosystems

Malcolm North, a research ecologist in the U.S. Forest Service who was not involved in the study, said that “the index is fairly simple and is a good first approach. But ecosystems are complex and their vulnerability to climate change is hard to accurately predict.”

“I do think this would be useful for organizations like the Forest Service as an initial index,” North said, “but each national forest develops its own 20- to 30-year forest plan built on the knowledge of the local forest ecosystems and regional climate change projections.”

Comer’s group recognized this and is starting to translate the output of the HCCVI into maps to help land managers understand the climate risk across the range of ecosystems.

“For example, in the pinyon juniper woodland that occurs across the intermountain West in the United States, in some portions we could say your vulnerability is high. And other places it’s sort of moderate,” he explained. He added that the index can even pinpoint the nature of the climate stress—for instance, whether it’s getting hotter and drier or hotter and wetter.

Sankaran said characterizing climate vulnerability will help land managers identify specific locations in ecosystems where exposure is likely to be high and allocate resources to such mitigation activities as restoration, establishing corridors to enhance connectivity and facilitate species movement, and fire and grazing management.

—Deepa Padmanaban (@deepa_padma), Science Writer

Citation: Padmanaban, D. (2022), Reevaluating ecosystems on the basis of climate change vulnerability, Eos, 103, Published on 17 June 2022.
Text © 2022. The authors. CC BY-NC-ND 3.0
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