An international collaboration of European research teams has just published an important study which directly attributes changes in mountain vegetation to climate change across the European continent. Whereas similar studies have been previously reported, this one provides a larger-scale picture for the impact which climate change is having on the flora which typically resides in alpine environments.

To directly attribute changes in alpine plant growth to global climate change is no small feat; these types of studies require measurements which take place over a number of years, as well as a geographic range which is large enough to make generalized conclusions concerning a large area of land. Since many alpine plant species are characterized by relatively slow growth and long lives, the measurement of such changes can only be conducted over a long period of time. For the study published earlier this week, these measurements were taken over the course of seven years, and encompassed virtually the entire continent of Europe, spanning 17 different mountain ranges in 13 different countries, as well as a latitudinal gradient spanning roughly 30 degrees. Ultimately, this wide range of variable ecosystems has allowed the researchers to make important generalizations concerning the impact which global climate, rather than any sort of local climate fluctuation, has on these alpine ecosystems.

Ottar Michelsen, one of the coauthors from the University of Science and Technology in Norway, highlighted this idea, suggesting that "you can find studies that have shown an effect locally, and where researchers try to say something more globally, but in this case, when you have so many mountains in so many regions and can show an effect, that's a big thing."

In 2001, four 1 X 1 meter plots were established at these alpine sites across Europe, each of which corresponded to one of the cardinal directions. These plots were placed between the treeline and mountain summit, where alpine meadows and their constituent vegetation usually exist. In 2008, these plots were then measured to determine changes in the type of plant cover which predominated at each location. At each site, a “thermophilization” value was assigned to each of the locations based on the change in types of plant species. These species were divided into two groups; those plants which thrive in low-temperature, high-altitude environments are known as cryophilic, and those that tend to thrive in a lower-altitude (and thus warmer) ecosystem are known as thermophilic.

When taken together, the results indicated that the degree of thermophilization across the European mountain sites was significant, and that the ability of cryophilic plant species to retain their 2001 distributions had decreased. The fact that these changes in mountain vegetation have occurred in a fairly short time period is alarming, and provides support for many of the prevailing theories concerning the impact which global climate change may indeed have on natural ecosystems. A 2007 study of alpine plant distributions in the Alps provides supporting evidence, and suggests that in certain areas, certain cryophilic species are already disappearing.

"The transformation of plant communities on a continental scale within less than a decade can be considered a rapid ecosystem response to ongoing climate warming," the researchers wrote. "Although the signal is not statistically significant for single mountain regions, it is clearly significant when data throughout Europe are pooled."

To supplement their research paper, the researchers utilized a map which depicts the continental temperature changes which were measured over the time span of the study, and when taken together with the observed changes in floral species, it appears that temperature differences of less than two degrees are more than sufficient to influence these floral distributions. As alpine meadows make up a very small portion of the total landmass globally, changes which occur with regard to these alpine plant distributions may ultimately be permanent, as long as nothing is done to significantly influence global climate change.

Original Research Article

Citation from 2007 study: Pauli, H. et al. Signals of range expansions and contractions of vascular plants in the high Alps: Observations (1994-2004) at the GLORIA master site Schrankogel, Tyrol, Austria. Glob. Change Biol. 13, 147-156 (2007).