Insects are almost half as numerous in areas affected by global warming and intensive agriculture as in less disturbed habitats.

This is the result of a study published this Wednesday in the journal

Nature

.

The researchers measured the abundance of insects and the number of different species in various regions of the world.

They compared these figures to pristine areas, less affected by climate change.

Result: global warming and intensive land use not only affect the total insect population but also reduce the number of species by 27%.

18,000 species studied

"The declines are greatest in the tropics," says Charlie Outhwaite, lead author of the study.

The work could also underestimate the decline of insects in the world, due to a lack of data in tropical regions.

Moreover, the human footprint in the “virgin” areas is already being felt.

The results are based on data for 18,000 species, collected between 1992 and 2012 from 6,000 locations.

Previous studies on the subject were done on a smaller scale.

This is “a quantitative analysis of the interaction between two drivers”, warming and land use change, “on large global data”, specifies the researcher.

“Catastrophic consequences” in sight

The fall of insects, crucial for the diet of many other species, has disastrous consequences.

About three quarters of the 115 most important food crops depend on pollination, including cocoa, coffee or cherries.

Some insects (the ladybird, the praying mantis or the wasp) are also necessary to control certain other insects harmful to crops.

The combined impacts of climate change and intensive agriculture, including the widespread use of insecticides, are worse than if these two factors acted independently.

In a previous study, researchers estimated that the number of flying insects had decreased by 80% in Europe on average.

“We cannot continue to lose species without ultimately causing catastrophic consequences,” commented British researcher Tom Oliver, who was not involved in the study.

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