Climate change puts ecosystems on run: U.S. study
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Global warming is causing climate belts to shift toward the poles and to higher elevations, to keep pace with which, the average ecosystem will need to shift about a quarter mile each year, said a new study led by scientists at the Carnegie Institution.
For some habitats, such as low-lying areas, climate belts are moving even faster, putting many species in jeopardy, especially where human development has blocked migration paths, said the report in the Dec. 24 issue of journal Nature.
"Expressed as velocities, climate-change projections connect directly to survival prospects for plants and animals. These are the conditions that will set the stage, whether species move or cope in place," said study co-author Chris Field, director of the Carnegie Institution's Department of Global Ecology.
The research team, which included researchers from the Carnegie Institution, Stanford University, the California Academy of Sciences, and the University of California, Berkeley, combined data on current climate and temperature gradients worldwide with climate model projections for the next century to calculate the "temperature velocity" for different regions of the world.
This velocity is a measure of how fast temperature zones are moving across the landscape as the planet warms, and how fast plants and animals will need to migrate to keep up.
The researchers found that as a global average, the expected temperature velocity for the 21st century is 0.42 kilometers (0.26 miles) per year. But this figure varies widely according to topography and habitat.
In areas of high topographic relief, where species can find cooler temperatures by climbing a nearby mountain, velocities are relatively low, while in flatter regions, such as deserts, grasslands, and coastal areas, species will have to travel farther to stay in their comfort zone and velocities may exceed a kilometer per year.
Plants and animals that can tolerate a wide range of temperatures may not need to move. But for others, survival becomes a race.
After the glaciers of the last Ice Age retreated, forests may have spread northward as quickly as a kilometer a year. But current ecosystems are unlikely to match that feat, the researchers said.
Nearly a third of the habitats in the study have velocities higher than even the most optimistic plant migration estimates. Even more problematic is the extensive fragmentation of natural habitats by human development, which will leave many species with "nowhere to go," regardless of their migration rates.
Protected areas such as nature reserves are generally too small to accommodate the expected habitat shifts.
According to the study, less than 10 percent of protected areas globally will maintain current climate conditions within their boundaries 100 years from now, which will present a challenge for many species adapted to highly specific conditions, especially if migration to new habitats is blocked.
An appreciation of climate velocities could stimulate discussions about sound management for climate change, from the design of nature reserves to the planning of assisted migrations for affected species, said Scott Loarie, a postdoctoral fellow at the Carnegie Institution and lead author of the paper.
It should also stimulate discussion about strategies for minimizing the amount of warming and thereby help slow climate velocity, he added.
