Alps in climate change: Many species adapt too slowly

In the Alps, it is getting warmer and warmer and spring is starting earlier and earlier. Many species living there can adapt their behaviour as well as their choice of habitat accordingly. But as it is shown in an overview study led by the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL) and the CNRS in France, which also includes numerous results from citizen science projects, these adaptations usually do not take place quickly enough.
Polyommatus damon (Damon blue), a low- and medium-altitude species, which is increasingly observed in the European Alps. (Photo: Yannick Chittaro)

In the Swiss Alps, the climate has warmed by about 1.8 °C since 1970. Many species living there react to this by moving up to cooler, higher regions. However, the habitat shifts observed so far are not sufficient for most species to keep up with the climatic changes. This is one of the findings of a review study led by the Swiss Federal Institute for Forest, Snow and Landscape Research WSL, which was recently published in the journal Biological Reviews.

The study also examined how the seasonal behaviour of many species is changing because spring is starting earlier and earlier in the Alps. It is the first to comprehensively summarise all these behavioural changes and habitat shifts. Yann Vitasse, a specialist in forest ecology at WSL, was part of an international team of biologists who analysed the data of more than 2,000 species (animals, plants and fungi) living in the Alps and neighbouring regions.

Migration often is not fast enough

Almost all the species studied are migrating to ever higher altitudes, especially the butterflies, which benefit from their ability to fly. Those are an exception, however, because –  unlike aquatic insects and many other groups of creatures  – they can probably migrate fast enough to cope with the increasing warming of the climate. The same is probably only true for the group of reptiles. "The fact that many species are moving up to higher altitudes is basically good news, because at least they are trying to adapt," says Yann Vitasse. "But most species do not manage to climb the necessary 60 to 70 metres of altitude per decade that they would have to overcome in order to continue living under their ancestral climatic conditions."

Trees and shrubs can also move to higher altitudes within a relatively short time, with up to about 33 metres of altitude per decade. But this is not enough to keep pace with current climate change. For other groups such as birds, ferns or wood-decomposing fungi, a much slower upward trend has been observed – less than 15 metres of elevation per decade. Amphibians and dragonflies have not even moved their habitat to higher altitudes at all. As larvae, these animals are dependent on water bodies as habitat and are therefore bound to water-rich sites.

Big differences in the activities in spring

Climatic changes in the Alps also lead to earlier snowmelt and increasingly warmer spring days. Plants, reptiles, migratory birds and land-dwelling insects such as butterflies or grasshoppers have responded by bringing forward their springtime activities - such as plant flowering - by an average of 2 to 8 days per decade. For other creatures such as birds, amphibians and semi-aquatic insects (especially dragonflies), there were no or only minor temporal shifts in their spring activities.

For Yann Vitasse, the sometimes strong differences between the various groups are problematic: "This development could lead to the different species no longer being able to coordinate their activities with each other chronologically, which is threatening for the long-term survival of the species as part of an ecosystem".

Citizens make an important contribution

However, the data used on a wide variety of creatures came not only from the already published scientific literature, but to a large extent also from citizen science projects. Two of them provided data that had never been published before: The PhenoForest database contains data on tree leaf litter since 1998; the info fauna data provide important insights into the migration patterns and changing behaviour of insects, reptiles and amphibians. In both projects, scientific amateurs provided the data through voluntary cooperation. This also applies in part to the data from MeteoSwiss on climate and those from the Sempach ornithological station on birds, which were also used in this study.

For Yann Vitasse, the contribution of citizens is of great importance for research: "In citizen science projects, citizens can collect together a much larger amount of observations and data in a much wider area than it would ever be possible in ordinary research projects." He is convinced that citizens will continue to make an important contribution to participatory research in the future.