Decline of insects in semi-natural forests

A recent study by the Eberswalde University for Sustainable Development (HNEE) entitled "Long-term drought triggers severe declines in carabid beetles in a temperate forest." (Droughts (or: dry years) lead to insect declines even in semi-natural forests) confirms the worrying decline of insects even in semi-natural ecosystems. Since 2015, the specific biomass has decreased by 89%. This decline correlates with the periods of drought in the last decade.

Prof Dr Andreas Linde and doctoral student Fabio Weiß have documented the changes in ground-dwelling insects (carabid beetles) in a semi-natural forest area north of Berlin over a period of 24 years. Although this forest was hardly utilised, the authors of the study found a significant decrease in the number and biomass of beetles as well as changes in the species composition.

The results confirm the indications of a progressive decline of insects even in near-natural ecosystems and confirm the increasing weather anomalies and dry years as important factors (drivers). One of the probable causes of the global decline in insects is climate change and the associated droughts in Europe, which have been unprecedented in recent centuries. Their influence on insects in forest ecosystems has been little studied to date.

"I was initially sceptical about reports of insect mortality, as the insect populations in our study area appeared stable for a long time. However, the sudden and sharp declines associated with the drought years cannot be denied." Says Prof Dr Andreas Linde. He is Professor of Applied Ecology and Zoology at the Eberswalde University for Sustainable Development. He has been collecting insect data with students in a wooded area near Eberswalde since 1995.

Fabio Weiß, a doctoral student at HNEE and Leuphana University Lüneburg, is researching the long-term development of forest insects in Germany and adds: "I am convinced that we are seeing the effects of climate change here."

This study is one of the first to analyse the effects of the recent dry years and heatwaves on forest insects in Central Europe. It was published in the international peer-reviewed journal Ecography. It is published by the Nordic Society Oikos and Wiley. It publishes research on ecological and biodiversity-related patterns in space and time.

Note on image material
The photos available here may be used in the context of reporting. Please note the copyright notice © HNEE / Fabio Weiß