A new pan-European study published in the journal Science shows that mountain plants across the continent are moving to higher altitudes, but that such upward shifts can lead to a reduction in species richness.
The paper is based on detailed surveys of 66 mountain summits distributed between the north of Europe and the southern Mediterranean sea. An international research group, led by the Austrian Academy of Sciences and the University of Vienna, and including Dr Jan Dick of the Centre for Ecology & Hydrology (CEH), mapped all plant species at each site in 2001 and 2008 using the same standardised procedures.
Increasing species numbers were only found on summits of northern and central Europe. By contrast, species numbers were stagnating or declining at nearly all sites in the Mediterranean region.
Dr Harald Pauli, from the Global Observation Research Initiative in Alpine Environments (GLORIA), the study’s lead author, said, “Our results showing a decline at the Mediterranean sites is worrying because these are the mountains with a very unique flora and a large proportion of their species occur only there and nowhere else on Earth.”
On summits further north in Europe, more plant species are prospering. This could be taken to indicate that these are much safer sites for alpine flowers. But Dr Michael Gottfried, from GLORIA’s coordination team said, “I'm afraid that this is not necessarily the case because the newly appearing plants are predominantly more widespread species from lower elevations and will pose increasing competition pressure on the rarer cold-loving alpine flowers.”
The uppermost tips of Mediterranean mountains are rather small patches of cold habitats, spread like islands over a sea of much warmer lowlands. Lowland areas, and the mountains are exposed to a characteristic dry season in summer. In the higher altitudes, precipitation mainly falls as snow during winter and spring, with snowmelt crucial for water supply of mountain plants during the arid growing season.
Dr Pauli added, “The observed species losses were most pronounced on the lower summits, where plants are expected to suffer earlier from water deficiency, than on the snowier high peaks. Climate warming and decreasing precipitation in the Mediterranean during the past decades fit well to the pattern of shrinking species occurrences. Much of the Mediterranean region is projected to become even dryer during the upcoming decades."
The paper, Recent Plant Diversity Changes on Europe's Mountain Summits, is published by Science (doi: 10.1126/science.1219033).
The GLORIA network aims to establish and maintain a site-based monitoring network for the long-term observation of high mountain plants. It began in Europe about a decade ago, when the sites used in this study were established. By now, the GLORIA monitoring programme was applied by more than 100 research teams and in over 100 mountain regions on six continents. Researchers will return to their sites every five to ten years.