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 Natureconcludes that global warming and intensive land use not only affect the total population of insects, which is almost halved, but that it also reduces the number of species by 27%.
Declines are greatest in the tropicstold Agence France-Presse the main author Charlie Outhwaite, of University College London.
She believes that the study may actually be underestimating the decline of insects worldwide, due to a lack of data in tropical regions and because in the least 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 small-scale, on a limited number of speciesnotes the researcher, while this one is
a quantitative analysis of the interaction between two motorsglobal warming and land use change,
on vast global data.
The fall of insects, which are 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 those of 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.
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.