Global warming influences the distribution of insects
Climate change has a major impact on the distribution of various insect species. There has been a decline in cold-loving insects in Switzerland over the past 40 years. Heat-loving species, on the other hand, have become more widespread. The idea that agriculture alone is to blame for insect extinction is proving to be increasingly wrong.
Wednesday, December 14, 2022
Since the 1980s, researchers have been observing a worldwide decline in the diversity, number and biomass of insects. The phenomenon is often referred to as "insect mortality". The main reasons for the decline have so far been habitat loss and changes in land use. A study by the research institutes Agroscope, WSL, FiBL and "info fauna" now shows that climate change is also having a major impact on the distribution of various insect species.
Winners and losers
The researchers analysed how the distribution of insect fauna in Switzerland has changed over the past 40 years. To do so, they analysed 1.5 million reports from laypeople and experts on the occurrence of butterflies, grasshoppers and dragonflies. The results of the study published in the scientific journal "Nature Communications" indicate that there has been no general decline in the insects analysed. However, there are both winners and losers among the species analysed. The species that have spread the most have increased their habitat by an average of 70 per cent. In contrast, the range of the species most affected by a decline shrank by an average of 60 per cent.
Decline in cold-loving species
As the authors of the study write in a press release, climate change is now having a major impact on the distribution of insects: "While habitat loss and changes in land use were previously the main reasons for the local disappearance of insect species, global warming is now also having a major impact on Switzerland's insect fauna." In the case of cold-loving species species that live in the Alps and pre-Alps are in decline. On the other hand, warmth-loving species from the lowlands have been able to expand their distribution areas. According to lead author Felix Neff from Agroscope, this development means that rare species are becoming even rarer and widespread species are continuing to increase.
Climate change in conjunction with changes in land use can have a particularly negative impact on the distribution of certain insects. For example, an intensification of grassland utilisation in combination with increasing drought in summer would have a particularly negative impact on insects. It must be expected that climate change will lead to large-scale changes in insect populations.
Diverse reasons for insect decline
There are many reasons for the observed decline in many insect species. There are also winners and losers on a global level. For example, a large meta-study concludes that the distribution of aquatic insects has increased in recent decades. In contrast, terrestrial insects have suffered losses. The expansion of urban areas and the associated sealing of surfaces certainly plays a major role in the decline of terrestrial insects. The habitat and food supply of many insects is becoming smaller. The increase in light sources also leads to "light pollution", which can have a negative impact on insects. However, the introduction of substances such as cleaning agents or pesticides into the natural environment can also have an impact on the distribution of insects. However, as the Agroscope study shows, climate change must also be increasingly taken into account as a factor in the spread of insect populations. However, the popular narrative that "pesticides are to blame for insect mortality" definitely falls short of the mark.
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