Decades of climate change have not left Europe's mountain vegetation unscathed. However, the changes observed do not always match expectations. As a new international study by a research team led by researchers from the University of Vienna, the Austrian Academy of Sciences and the BOKU University shows, alpine vegetation has shifted significantly towards warmth-associated species. However, the direct link between this so-called thermophilisation and local warming is surprisingly weak. The study has recently been published in the prestigious journal Nature Ecology and Evolution.
For the study, the international research team analysed data from 724 long-term monitoring plots on 53 mountain summits, spread across all major European mountain regions. These plots were surveyed a total of four times over a period of 21 years as part of the global GLORIA monitoring network, the most comprehensive monitoring programme to date on the effects of climate change on mountain summit vegetation.
The results show that warmth-associated plant species are now more common in many places than they were at the beginning of the monitoring program. At the same time, temperatures on the summits studied have risen. Surprisingly, however, the extent of thermophilisation at a monitoring plot could only be poorly explained by the warming measured there.
"Our data clearly show that vegetation on European mountain summits is changing and that warmth-associated species are becoming more common," explains biodiversity researcher Johannes Hausharter from the University of Vienna, the study's lead author. "However, the rate of these changes does not appear to depend solely on rising temperatures."
The study thus provides new insights into the complex mechanisms driving changes in alpine vegetation and shows that the consequences of climate change, even in sensitive ecosystems such as those of Europe's high mountains, are more nuanced than has often been assumed.
Local conditions override the effect of climate
The researchers compared the observed changes in vegetation with a whole series of different temperature-related climate indicators from various data sources. Despite this exceptionally comprehensive dataset, the link between rising temperatures and changes in vegetation remained limited at the local level.
The integration of the monitoring plots within the surrounding vegetation proved to be particularly important. “How alpine vegetation responds to climate change depends not only on how many degrees warmer it gets, but also on whether other warmth-associated species are already present,” says project leader Stefan Dullinger from the University of Vienna.
