An animal sign of climate change: The warming not only drives up the readings on thermometers, but also butterflies, researchers report. The range of Alpine butterflies has shifted 300 meters uphill within 60 years, their study shows. As with other aspects of climate change, adaptation limits are also in sight in this case: At the summit, the mountain butterflies’ alternative options are over.
The world is changing – man-made global warming is becoming more and more evident: The trend is evident in the changes in climatic mean values in recent decades as well as in the more frequent weather extremes – such as droughts or, in the current case, through heavy rainfall with catastrophic floods. The climatic changes are also reflected in shifts in flora and fauna in many parts of the world: animals and plants follow the geographical shifts in living conditions to which they are adapted. Some studies already show that the distribution areas of many species are not only shifting in the north-south direction, but also in terms of altitude.
On the way to the summit
The current study by the international team led by Jan Christian Habel from the Paris-Lodron University in Salzburg documents such a process particularly impressively. “Hot and dry summers are becoming more and more common in Central Europe – we are also seeing these effects of global climate change in the supposedly cooler mountain regions,” says Habel. “We have therefore examined how mountain butterflies in the state of Salzburg have adapted to these changed environmental conditions over the last 60 years.” For this purpose, the researchers analyzed historical records of 5836 butterfly observations from local databases and combined the results with detailed information on climatic development in linked to the region.
“Our results clearly show that the habitats of butterflies have been shifting to higher and higher altitudes in the course of climatic changes for several decades,” summarizes first author Dennis Rödder from the Alexander König Zoological Research Museum in Bonn. On average, the researchers were able to detect a shift in the distribution of the 37 butterfly species examined by about 300 meters uphill between 1960 and 2019.
“Butterflies are highly sensitive to climate changes and follow their specific ecological niche, so to speak, in which they find the environmental conditions they need to survive,” explains co-author Thomas Schmitt from the Senckenberg German Entomological Institute in Müncheberg. So they adapt flexibly to change and thereby secure their survival, one might think. “But there is a problem with mountain species: the vertical shifts are finite,” emphasizes the scientist. Their entire habitat is becoming smaller – due to the topography – and the question remains what happens when the species have reached the peaks ”.
A study with a symbolic character
In addition, the shifting process already creates ecological problems, the study shows: Interactions between species are disturbed or break away completely. As the scientists report, some of the butterflies’ forage plants react more slowly to climatic changes than their consumers. “In simple terms, one could say that the plants cannot migrate quickly enough due to their lower mobility. An example of this is the Natterwurz nacreous butterfly (Boloria titania), whose range overlaps less and less with one of its preferred forage plants, the snake knotweed (Bistorta officinalis), ”says Schmitt. In addition, some specialized plant species could lose their pollinators as the moths migrate and thus disappear.
In addition to the importance for alpine ecosystems, the researchers see their study results as a particularly impressive example of the effects of climate change. “The silent summit storm of the butterflies is a beacon to illustrate the explosive nature of the climate crisis – the effect should be understood as a wake-up call: We are in the midst of a fundamental, rapid change in the environment,” the scientists write.
Source: Leibniz Institute for the Analysis of Biodiversity Change, specialist article: Scientific Reports, doi: 10.1038 / s41598-021-93826-0