Climate change and abnormal seasonal weather have a far bigger impact on insect populations than previously thought, scientists say.
A new study exploring insect biomass changes shows that unusually wet summers or warm winters have telling impacts on populations.
German researchers found that when several such weather anomalies occur over a short period of time it can lead to a decline in insect biomass on both a large scale and in the long term.
The study concluded that the accumulation of such weather anomalies alongside climate change is an important driver in insect decline – and pleaded for more high-quality habitats to be preserved for insects.
The German and Swiss research team study began when Dr. Jörg Müller, a Professor of Animal Ecology at the Biocentre of Julius-Maximilians-Universität Würzburg (JMU) in central Germany, noticed in the spring of 2022 that there seemed to be an abundance of insects in the forests and meadows around him.
In contrast, however, more and more scientific studies published in recent decades have instead pointed towards the conclusion that insect populations are declining across the world.
One such study, from a group led by Dutch researcher Caspar A. Hallmann in 2017, shockingly revealed that the insect biomass in German nature reserves decreased by more than three-quarters in the 27 years between 1989 and 2016.
“The data from the study showed that there was a dramatic collapse in 2005 and no recovery in the years that followed,” Dr Müller commented.
Dr. Müller and his team decided to identify the underlying causes of insect population changes and formed an interdisciplinary team of researchers from TU Dresden, TU Munich and the University of Zurich.
The team’s first task was to find out whether there was more insect biomass than usual in 2022 – which they discovered there was.
Dr Müller explained: “We found a biomass that was almost as high on average as the maximum values from the Hallmann study.
“And our 2022 maximum was higher than all values Hallmann had ever determined – this value, by the way, comes from the forest of the University of Würzburg.”
The researchers next re-analyzed the data from the Hallman study of 2017 alongside newly-prepared weather data including information on temperatures and precipitation during sampling.
Weather anomalies – deviations from long-term averages – during the different phases of an insect’s life from egg to larva, pupa and adult were also taken into account.
The researchers found that, in the years that followed 2005, weather influences were predominantly negative for insects.
At times the winters were too warm and dry whilst at others the spring or summer was too cold and wet.
In contrast, the weather in 2022 was consistently favorable for insects, as was the previous summer – helping to shed light on the high insect biomass Dr. Müller had noticed.
Dr. Annette Menzel, a professor of eco-climatology at the Technical University of Munich, says the study should raise awareness of the influence climate change already has on insect populations.
“We need to be much more aware that climate change is already a major driver of the decline of insect populations,” she said.
“This needs to be thought about much more in science and conservation practice.”
The team behind the study – published in the journal Nature – also called for more high-quality habitats for insects to mitigate the extinction risks of threatened species – insisting current efforts to protect insects are even more urgent than previously thought.
This common task affects agriculture as well as traffic and settlement areas – in other words, all areas where high-quality habitats are reduced or impaired.
Dr. Müller also suggested establishing a biomass monitoring system for the whole of Germany which would make it possible to continuously measure the upward and downward trends of insect populations and include them in further analyses.
Produced in association with SWNS Talker
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