"It's not the weather - we humans are causing insect mortality"

What role do you think climate change and its weather phenomena play?

Climatic changes definitely influence insect populations. This has actually been known since the 1950s - insects are thermophilic and therefore react strongly to temperature and humidity. In a sense, weather and climate are the "background noise" that has always had an effect on insects. The trick now is to precisely identify influences that go beyond this background noise. There are many experimental studies on the effects of fertilisation, crop protection, soil cultivation, drought, temperature increase and increased CO2 content of the atmosphere on insects, in which causal relationships can be wonderfully compared with each other.

According to your assessment and your studies, what are the main causes of insect mortality?

Not the weather - we humans are causing insect mortality. In my opinion, the conversion of a diverse, colourful landscape into building land and intensive agriculture with monoculture and the use of chemicals are the main causes. For example, in a STUDY IN 2015, we specifically analysed the biodiversity of plants, butterflies, grasshoppers and other groups in nature reserves. Biodiversity was always particularly low when there was a lot of arable land in the vicinity - and when the protected areas were very isolated from each other.

In 2017, the Krefeld study revealed an insect decline of 75 per cent. Does the Nature study provide any surprising insights into the causes?

The study does not provide any new insights and rather hinders the debate about the causes of insect extinction. The very approach is wrong: we need experimental study results, such as on mixed crop cultivation(DIVERSIFY PROJECT), on the avoidance of pesticides(FINKA PROJECT) or on flower strips(NAPA PROJECT), in order to develop patterns and models and to see what we can do differently in the future. The authors present models that are too simple and demonstrably ignore important influencing variables such as land use in particular. The Krefeld study was not originally designed to discover changes in land use - so it is no wonder that hardly any causal relationships can be found in such a heterogeneous data set. You cannot understand the dynamics of a system simply by looking at it. There is an excellent basis for this from structured biodiversity monitoring, for example from the umbrella organisation of German avifaunists or the FEDERAL OFFICE FOR NATURE CONSERVATION. We are currently analysing this data as part of a research and development project.

How do you view the Krefeld study and its further development?

The authors of the "Krefeld Study" themselves noted that the causes of the decline in insects cannot be precisely proven with the available data. The study looks back at the insect population in German nature reserves over the past 27 years and has stimulated a debate about causes and protective measures, but also about our knowledge of native species. This knowledge is very patchy. This is why many useful studies have been initiated since 2017 with the support of the German government. For example, the LIB study GBOL-DARK TAXA. We are still discovering hundreds of new species in Germany, not to mention introduced species that can only be detected using modern molecular methods such as those used in GBOL. Only if we can categorise these species will we be able to say how many are being lost and why. We need to conduct long-term research here and at the same time take action against insect extinction now.

Do we already have enough data for protective measures? What is the LIB contributing here?

We have various research programmes underway, including EU-wide programmes, in cooperation with farmers (for example the "BIOMONITOR4CAP"), where we use modern monitoring methods to generate data from which we can identify the drivers of the biodiversity crisis. Enough has long been known to finally implement effective measures to protect insects - measures that are already known to be effective from field trials. Our studies to date clearly show that biodiversity-promoting measures such as mixed crop cultivation, reduction of pesticides or perennial flower strips promote insect biodiversity. We are also conducting research in forests and gardens and have identified specific solutions here. Instead of looking back, we should look forward and take action for a biodiversity-friendly future.