Wildlife & Biodiversity

Climate change influences rise and fall of insect populations: Study

A study by German researchers tried to find answers to whether an insect apocalypse is actually going on or not

By Rohini Krishnamurthy
Published: Thursday 28 September 2023
A water strider. Photo: iStock_

Insect populations are widely influenced by weather anomalies, with decreasing numbers observed during unfavourable conditions and a spike in normal periods, according to a new study.

The study published in Nature tries to resolve a debated topic: Are insect populations declining? A number of studies have reported a decline in insect populations and diversity while others have questioned this.

“Our results resolve so far contrasting results on biomass, species extinction and so on,” Jörg Müller from the University of Würzburg Biocenter in Germany and one of the study’s authors told Down To Earth.

A previous study reported that insect biomass in protected areas of Germany dropped by more than 75 per cent between 1989 and 2016. “The data from the study show that there was a dramatic collapse in 2005 and no recovery in the years that followed,” Müller said in a statement.

Müller, however, sensed an increase in insect biomass in 2022. So he wondered if a large amount of insects “he felt in 2022 could be real?”

He and his team tested if the insect biomass had indeed risen in Germany in a wide range of open habitats including meadows and arable fields in 2016, 2019, 2020 and 2022.

“We found a biomass that was almost as high on average as the maximum values from the study [which found a decline of more than 75 per cent between 1989 and 2016,” he said. 

The researchers suspected that climate change played a role in the decline. Other factors such as habitat loss and urbanisation, pollution (from synthetic pesticides and fertilisers, and biological factors (pathogens and introduced species) have also been linked.

Their analysis showed that the increase between 2016 and 2022 corresponds to changes in weather conditions.

The weather in 2022 was consistently favourable for insects, as was the summer of 2021. This, according to the researchers, explains the high insect biomass observed in 2022.

Next, the researchers analysed the study that reported a more than 75 per cent decline in insect biomass between 1989 and 2016.

Post 2005, weather influences were not suitable for insects. For example, the winter was too warm and dry and the spring or summer, sometimes was too cold and wet.

Temperatures and precipitation affect insect populations at various stages of their life cycle.

For example, the insects’ survival depends on winter conditions and the last weather conditions such as spring or summer, the researchers wrote in their study.

“We need to be much more aware that climate change is already a major driver of the decline of insect populations. This needs to be thought about much more in science and conservation practice,” Annette Menzel, professor of ecoclimatology at the Technical University of Munich, said in a statement.

There are implications across the food chain. Birds feeding on insects strongly felt the pinch. The decline in insect biomass also accompanied a corresponding drop in bird abundance between 2005 and 2019.

Muller said future studies should test out this hypothesis with new approaches using modelling, experiments, and well-selected field studies.

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