Climate change has been happening in central Europe for a long time, and it is no secret that it is affecting the populations and distribution of animals and plants. Insect trends, in particular, are a growing cause for concern, as numerous studies have shown their decline. The evolution of the populations of our insect species over the past decades is a question explored by TUM’s BioChange Lab. “It is not only the climate that is changing, but also the type and intensity of land use. This includes agriculture, forestry, urban areas and transport infrastructure,” says Dr Christian Hof, head of the BioChange research group at TUM.

While changes in flora and fauna can be well documented in certain areas or for specific species, data for insects and especially over extended periods is very scarce. It is therefore difficult to draw general conclusions about changes in populations of insect species and the factors driving biodiversity change. Yet it is precisely findings about species population changes over time, as well as factors such as land use and climate, that inform conservation plans to protect species, biotopes and habitat. climate.

A wealth of data

Thanks to the tireless efforts of volunteer and professional nature observers, we have data sets on the occurrence of various species in Germany. A particularly useful resource is the Species Mapping Database (ASK) of the Bavarian State Office for the Environment. The ASK is Bavaria’s national register of animal and plant species and currently has around 3.1 million species records. It is a central data source for the daily work of nature conservation authorities and for the LfU’s compilation of red lists of endangered species.

Using complex statistical methods, researchers from the TUM Chair of Terrestrial Ecology evaluated the valuable ASK data and analyzed the population trends of more than 200 insect species in Bavaria – around 120 butterflies, 50 orthopterans and 60 dragonflies. . Together with many other experts, they showed that in all these insect groups there was an increase in the populations of heat-loving species and a decline in species adapted to cooler temperatures.

Species like the heat-loving scarlet dragonfly are benefiting from climate change

Insects have been divided into those that prefer warm temperatures and those that prefer cold temperatures based on empirical data. “We determined the temperature preferences of each species using data on their distribution in Europe and the average temperature in this area. In other words, species with a predominantly northern distribution are cold-adapted species, and species with mainly southern European distribution are warm-adapted species,” explains Eva Katharina Engelhardt, PhD student at the TUM BioChange Lab.

Heat-adapted species include the blue stick (butterfly), European tree cricket and scarlet dragonfly. “The scarlet dragonfly is one of the most well-known beneficiaries of global warming. The dragonfly, more common in the Mediterranean region, first appeared in Bavaria in the early 1990s and is now widespread,” Hof tells us. .

Cold-adapted species include Thor’s Fritillaria, Green Mountain Grasshopper, and White-faced Darter.

Populations of butterflies, orthoptera and dragonflies affected by climate change

“Our comparisons of different groups of insects revealed significant differences,” says Engelhardt. “While there was more decline than increase in butterfly and orthoptera species, the trends for dragonflies were largely positive.” One possible reason for this is the improvement in water quality in recent decades, a change that particularly benefits dragonflies, which depend on aquatic habitats. Habitat specialists, ie species adapted to specific ecosystems, have declined. Butterflies such as heather or blue bilberry are specialists in this example since they are dependent on very specific habitats.

“Our study highlights the complex effect of climate change on our insect fauna. Our work is also an example of how modern data analysis approaches can be used to obtain fascinating results from existing datasets. The conservation work of volunteers and agencies often generates the data, but they are rarely systematically evaluated. This should happen much more often through collaborations like ours,” says Dr. Diana Bowler of the Center German Institute for Integrative Biodiversity Research (iDiv).

Johannes Voith, entomologist at the Bayerisches Artenschutzzentrum (Bavarian Center for Species Conservation) at the LfU, adds that “in the context of the collaboration with TUM in particular, we benefit from the knowledge acquired. Then we plan to create dynamic distribution maps for each species. .”