Plants Have Unexpected Response To Climate Change

  • Date: 09/08/14
  • Science Magazine

Not all species flee rising temperatures. As the mercury has inched upward across western North America over the last 40 years, many plant species have moved downhill, toward—not away from—warmer climates, according to the results of a new study.

The finding adds to growing evidence that temperature isn’t the only factor influencing how Earth’s life will respond to climate change.

“This is a very cool study and demonstrates what many of us have been saying—that we will get surprises,” writes Camille Parmesan, a climate change biologist at Plymouth University in the United Kingdom, in an e-mail to Science. She was not involved with the study.

Like animals, plants require specific environmental conditions—such as the right temperature, moisture, and light levels—in order to thrive. Even small changes in environmental parameters can affect the reproduction and survival of a species. As global temperatures rise, both animal and plant populations are projected to gradually shift toward northern latitudes and upward to higher elevations where temperatures are cooler in order to stay within their ideal range of environmental conditions.

In an effort to understand how plants may cope with changing climates, researchers at the University of Washington, Seattle, compiled geographic coordinate data for the locations of nearly 300 plant species within seven topographically distinct regions across western North America, ranging from the western Sierra Nevada mountain range in Nevada to the eastern Rocky Mountain Foothills of northern Canada, spanning the last 40 years. They then compared these findings with changing climate conditions, such as temperature, rain, and snowfall. The study is the most extensive of its kind to date.

The results of the analysis were unexpected. More than 60% of plants shifted their distributions downward, toward warmer, lower elevations—despite significant climate warming across the regions under study, the team reported online on 24 July in Global Change Biology. Even more striking, all plants within a region—regardless of species—moved in the same direction.

“Initially, we thought there was something wrong with our analysis—species distributions are expected to shift upward, not downward,” says team leader and plant ecologist Melanie Harsch. “But we redid the analysis and we got the same results.”

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