Plants moving to lower and warmer elevations in a warming world

A news release out of the University of California at Davis says, “study shows plants moved downhill, not up, in warming world.”

In a paper published last month in the journal Science, a UC Davis researcher and his co-authors challenge a widely held assumption that plants will move uphill in response to warmer temperatures. It turns out that plants respond more to moisture. The results are based on historical data collected by the U.S. Forest Service since the 1930s

Between 1930 and 2000, many California plant species moved downhill an average of 260 feet.  Jonathan Greenberg, an assistant project scientist at the UC Davis Center for Spatial Technologies and Remote Sensing said, “While the climate warmed significantly in this period, there was also more precipitation. These wetter conditions are allowing plants to exist in warmer locations than they were previously capable of.”

While the news release does not mention it, let me conjecture that increased CO2 availability may have played a role in the plants ability to move downhill despite warmer temperatures encountered at lower elevations. Plants do not need to open their stomata as much or as often for CO2 intake and therefore do not lose water through transpiration.

Many forecasts say climate change will cause a number of plants and animals to migrate to new ranges or become extinct. That research has largely been based on the assumption that temperature is the dominant driver of species distributions. However, the new study reveals that other factors, such as precipitation, may be more important than temperature in defining the habitable range of these species.

The findings could have global relevance, because many locations north of 45 degrees latitude (which includes the northernmost United States, virtually all of Canada and Russia, and most of Europe) have had increased precipitation in the past century, and global climate models generally predict that trend will continue, the authors said.

The study is titled “Changes in climatic water balance drive downhill shifts in plant species’ optimum elevations.” Greenberg’s co-authors are: graduate student Shawn Crimmins (the lead author), assistant professor Solomon Dobrowski (a UC Davis alumnus) and research analyst Alison Mynsberge, all of the University of Montana; and assistant professor John Abatzoglou of the University of Idaho.

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