Insect populations are almost half as numerous in areas affected by global warming and intensive agriculture as in the least disturbed habitats, according to a study published on Wednesday which is concerned about the consequences for the pollination of crops.
The researchers measured both the abundance of insects and the number of different species present in various regions of the world, comparing these figures to areas that were pristine and less affected by climate change.
The study published in the journal Nature concludes that global warming and intensive land use not only affect the total insect population, which is almost halved, but also reduces the number of species by 27%.
“Broad Global Data”
“The biggest declines are in the tropics,” said lead author Charlie Outhwaite, of University College London, saying the study may actually be underestimating global insect declines. This is due to a lack of data in tropical regions and because in the less disturbed areas used as a point of comparison, the imprint of humans is already sensitive.
The findings, consistent with previous studies of insect population declines, are based on data on 18,000 species, collected between 1992 and 2012 from 6,000 locations.
“Previous studies were on a small scale, on a limited number of species,” notes the researcher. While this is “a quantitative analysis of the interaction between two drivers”, warming and land use change, “on large global data”.
Disastrous consequences
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.
Certain insects such as ladybugs, praying mantis or wasps are also necessary to control certain other insects harmful to crops.
The study also shows that the combined impacts of climate change and intensive agriculture, including the widespread use of insecticides, are worse than if these two factors acted independently.
80% fewer flying insects in Europe
For example, even without climate change, converting a rainforest 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. Aridification reinforced by global warming.
Until now, intensive agriculture and habitat destruction have been the main drivers of insect decline. In a previous study, researchers estimated that the number of flying insects had fallen by 80% in Europe on average, leading to a drop in bird populations.
“We cannot continue to lose species without ultimately causing catastrophic consequences,” said Tom Oliver of the University of Reading, who was not involved in the study.
The new study discusses ways to allow insects to survive, such as extensive agriculture with fewer phytosanitary products and surrounded by natural habitats.