State ecosystems projected to shrink by century's end

Posted: Monday, October 25, 2010

Roughly 60 percent of Alaska's ecosystems may shift in response to climate change by the end of the 21st century, according to the results of a two-year study released in September by University of Alaska Fairbanks.

The study, a collaboration between the U.S. Fish and Wildlife Service and scientists from the University of Alaska, concluded that western tundra, Arctic and Interior ecosystems will diminish the most from current conditions by 2100. It also projects the more mild climate of Southcentral Alaska could become the dominant ecosystem for Alaska in the same period.

Entitled "Connecting Alaska Landscapes into the Future," the project's purpose is to provide a guide for resource managers and stakeholders to maintain "landscape-level connectivity" between ecosystems as they change in response to shifting climate conditions.

The study examined the potential impacts on barren-ground caribou, Alaska marmots, trumpeter swans and reed canary grass, and attempts to project where these species and vegetation may move under altered climate.

Understanding Alaska's changing climate is vital for conservation and development interests alike as habitats shift or diminish and wildlife adapts. For example, an area not important to trumpeter swans today could become a critical habitat in 50 years as its preferred habitat shifts west and north.

The study is available at SNAP stands for Scenarios Network for Alaska Planning and is a statewide, University of Alaska-based program.

The study attempted to identify where the ecosystems would remain similar to today in 2100 - known as "refugia" - and establish migratory connectivity through conservation measures between current ecosystems and the shifting ecosystems expected to take form in the coming decades.

It divided Alaska into six distinct biomes, which are areas based on assembled species, existing land cover, current climatic conditions and projected climate change.

The Arctic biome and the Alaska Boreal (roughly similar to the Interior region) biome are projected to diminish by 69 percent by the end of the century. The western tundra is projected to diminish by 54 percent. Western tundra is considered to be the most vulnerable biome with the least resilience for conservation purposes and is further at risk from rising sea levels.

The Arctic biome now accounts for 25 percent of state land; by 2100 it is projected to encompass a mere 8 percent. The Alaska Boreal (Interior) biome, now 29 percent, is projected to shrink to 9 percent. The western tundra biome, now 15 percent of the state reaching from Selawik to Pilot Point and west to the coast, is projected to shrink to 6 percent by 2100.

The characteristics of the western tundra biome are projected to all but disappear from its current location. The projections developed by researchers indicate that the western tundra biome will shift to a narrow strip bordering the southern edge of the reduced Arctic biome by 2100.

The dominant biome in Alaska by 2100 is projected to be what's described as the Boreal Transition. Under current conditions, the Boreal Transition biome accounts for 14 percent of the state and stretches from the top of the Alaska Peninsula in a banana shape following the Alaska Range and curving over the Southeast panhandle.

By 2100, the Boreal Transition biome is projected to account for 39 percent of the state, forming a massive triangle shape with Tok, Kotzebue and Bethel roughly at its corners.

The modeling was developed using selected Global Circulation Models from the Intergovernmental Panel on Climate Change, or IPCC. Researches narrowed the IPCC models to the five most accurate for predicting northern climate and used a mid-range projection from the IPCC to estimate increased greenhouse gas emissions.

In the study, the researchers note that more severe projections for greenhouse gas emissions are now considered more likely, given recent trends.

From there, researchers projected precipitation and temperature for the various biomes over the next century and modeled how they would change from present climatic conditions.

Three significant factors were not considered in modeling for connectivity between shifting biomes - sea level rise, permafrost and fire disturbance.

The effects of sea level rise requires more modeling and better mapping, as some areas of Southeast and Southcentral are actually seeing land surface rising in response to loss of glacial ice and tectonic deformation.

Predictive models for how climate change affects permafrost are still being developed, as are those for the dynamics of fire disturbance on vegetation as a result of climate change.

Overall, the study is not intended to be the final word, but a jumping-off point to expanded research.

"Our hope is that this document will serve as a jumping-off point for lively discussion and debate, and will help inform and inspire new research, as well as efforts to ground-truth and validate our models," said Nancy Fresco, SNAP coordinator.

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