Paris. Climate change and the intensive use of land for agriculture have already caused a 49 percent reduction in the number of insects in the most affected areas of the world.
A new study, conducted by researchers at University College London (UCL) and published in Nature, is the first to identify that the interaction between rising temperatures and changes in land use is causing widespread losses in many insect groups around the world.
Charlie Outhwaite, from UCL’s Center for Biodiversity and Environment Research and lead author of the study, explained: “Many insects appear to be highly vulnerable to human pressures, which is worrying as climate change worsens and agricultural areas continue to expand.
“Our findings highlight the urgency of taking action to preserve natural habitats, curb the expansion of high-intensity agriculture, and reduce emissions to mitigate climate change,” he added.
The researchers measured both the abundance of insects and the number of different species present in various regions of the world, comparing these figures with those of virgin areas less affected by climate change.
The study also concluded that not only is the total insect population being affected, which has been reduced by almost half, but also the number of species is decreasing by 27 percent.
“The falls are higher under the tropics,” said Outhwaite.
He considers that the study may underestimate the decline of insects in the world due to the lack of data in tropical regions and that in the less disturbed areas, used as a comparison, the human footprint is already significant.
The results, in line with previous studies on the decline of insect populations, are based on data from 18,000 species, collected between 1992 and 2012 in 6,000 locations.
“Previous research was on a small scale, with a limited number of species,” he clarified.
The new study, instead, is “a quantitative analysis of the interaction between two engines”, warming and land use change, “on large global data sets”.
Disastrous consequences
The decline in numbers of insects, crucial to the diet of many other species, has disastrous consequences.
Around three quarters of the 115 most important food crops depend on pollination, such as cocoa, coffee and cherries.
Some insects, such as ladybugs, praying mantises, and wasps, are also needed to control other insects that damage crops.
The study also shows that the combined effects of climate change and intensive agriculture, including the widespread use of insecticides, are worse than if the first two factors acted separately.
For example, even without climate change, the conversion of a tropical forest to agricultural land causes the area to warm due to the loss of vegetation that provides shade and maintains moisture in the air and soil.
This aridification is reinforced by global warming.
In an earlier study, researchers estimated that the number of flying insects had declined by an average of 80 percent in Europe, leading to a decline in bird populations.
“We can’t keep losing species without eventually having catastrophic consequences,” said Tom Oliver of the University of Reading, who was not involved in the study.
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