Nature Today

Insect die-off: even common species are becoming rare

Technical University of Munich
09-FEB-2018 - Together with their colleagues from the Senckenberg German Entomological Institute, scientists of Technical University of Munich (TUM) were able to show that currently widespread insects are threatened with a serious decline in species diversity in the near future. The research team lists fragmentation of habitats and intensification of agriculture as reasons for the decline of these generalists.
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The number of insects continues to decrease - in some regions, a dramatic decline by up to 75 percent has been recorded in recent decades. "Until now, we assumed that it is primarily the specialists among the insects, i.e., animals that depend on a specific habitat, that are threatened with extinction," explains Professor Dr. Thomas Schmitt, director of the Senckenberg German Entomological Institute, and he continues, "In our recent study, we were able to show that even so-called "ubiquitous species" will be facing massive threats in the future."

Fragmentation of habitat

Meadow brown,rRinglet and hairstreak species rarely occur in large densitiesIn their study, the team of scientists explains that species with low habitat requirements depend on the exchange between different populations. "Our studies clearly show that widespread species have a much more diverse intraspecific gene pool than species that are adapted to a specific habitat," explains Dr. Jan Christian Habel of the Technical University in Munich, and he continues, "Once these animals - due to the fragmentation of their habitats - lose the opportunity to maintain this genetic diversity by means of exchange, they will no longer be able to adapt to changing environmental conditions in the future."

The insect researchers from Munich and Müncheberg refer to a "temporal shift in the potential causes for the decline of species." Initially, it is primarily those insects that specialize in a particular ecosystem, e.g., the Mountain Apollo (Parnassius apollo) butterfly, which will be threatened by the loss of high-quality habitats. But over time and with the further deterioration of habitats as well as the collapse of entire habitat networks, the threat to widespread, 'undemanding' species such as the Pearly Heath (Coenonympha arcania) also increases. 

Isolated reserves are no longer sufficient

"In terms of practical nature conservation, these results signify that in the future it will no longer be sufficient to preserve small, isolated reserves - while these benefit specialized species with a simple genetic structure, the bulk of species that depend on an exchange between local populations will lose out in the medium to long term," predicts Schmitt, and he adds in closing: "This will lead to a further decline of numerous insect species - with dramatic consequences for entire food webs and ecosystems."

This perspective is published in the scientific journal Biological Conservation.

Text: Technical University of Munich (TUM)
Photos: J. Habel, Technical University of Munich (TUM)

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