Climate change and agriculture halve insect populations

In recent years, researchers have reported alarming decreases in both the number of populations and the diversity of insects. These phenomena are often linked to the impacts of global climate change and habitat loss due to industrial agriculture. According to a study published today (April 21) in Natureclimate change and agriculture appear to have a synergistic effect on insect biodiversity, each amplifying the declines caused by the other.

For the study, researchers from University College London (UCL) analyzed data from more than 750,000 samples of nearly 18,000 insect species that were collected from 6,000 sites around the world over the last 20 years. They compared changes over time in the numbers reported by the samples on insect populations and biodiversity to mean and maximum temperatures as well as land use at each site. Each area was classified as having primary vegetation or low or high intensity agriculture. Researchers have found that rising temperatures are linked to greater population reductions and the loss of more species in areas where natural habitats have been cleared to make way for agriculture than in undeveloped regions. . Areas with temperature increases but undisturbed insect habitats, or disturbed habitats but relatively stable temperatures, suffered lower losses. In high-intensity agricultural areas affected by temperatures rising to one standard deviation above baseline fluctuations, such as some sites in Brazil, insect numbers dropped by up to 49% and the number of species present fell 27%.

“In this case, habitat loss and climate change can often be worse than if they acted alone, as one can worsen the impact of the other and vice versa,” said Charlotte Outhwaite, author of the study and ecologist from UCL. Associated Press. “We miss part of the picture if we only look at these things individually.” Part of the problem, says Outhwaite, is that agricultural development is reducing tree cover, making rising temperatures even more deadly for insects unable to find shade. Those who survive may then migrate to a new area that does not suit them as well.

See “Biggest winter bee decline in 13 years: survey”

The scale of the study and the number of samples included make the results particularly believable, University of Connecticut entomologist David Wagner, who was not involved in the work, told the AP.

“Our results underscore the urgency of action to preserve natural habitats, slow the expansion of high-intensity agriculture and reduce emissions to mitigate climate change,” Outhwaite said. BBC News.

See “Questions and Answers: Global insect decline due to ‘death by a thousand cuts’”