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Rising temperatures caused by the worsening climate crisis and the intensive use of land for agriculture have together resulted in a 49 per cent reduction in the number of insects living in the most severely affected parts of the world, UK scientists have warned.
The study by researchers at University College London (UCL) is the first to identify how the interaction between increasing temperatures and land-use changes is driving “widespread losses in numerous insect groups across the globe”.
The scientists warned that it is likely their research represents only “the tip of the iceberg” of the toll human activity is taking on insect life.
As a result of collapsing insect populations, human health and food security are at increasing risk, the researchers said.
Lead author Dr Charlie Outhwaite, from UCL’s Centre for Biodiversity & Environment Research, said: “Many insects appear to be very vulnerable to human pressures, which is concerning as climate change worsens and agricultural areas continue to expand. Our findings highlight the urgency of actions to preserve natural habitats, slow the expansion of high-intensity agriculture, and cut emissions to mitigate climate change.
“Losing insect populations could be harmful not only to the natural environment, where insects often play key roles in local ecosystems, but it could also harm human health and food security, particularly with losses of pollinators.”
She added: “Our findings may only represent the tip of the iceberg as there is limited evidence in some areas – particularly in the tropics, which we found have quite high reductions in insect biodiversity in the most impacted areas.”
The research team carried out the study by analysing a large dataset of insect abundance and species richness from areas across the globe, including three-quarters of a million records for nearly 20,000 insect species.
They then compared insect biodiversity in different areas depending on how intensive agriculture is in the area, as well as the level of climate warming the area has experienced historically.
They found that in areas with high-intensity agriculture and substantial climate warming, the number of insects was 49 per cent lower than in the most natural habitats with no recorded climate warming, while the number of different species was 29 per cent lower.
Tropical areas saw the biggest declines in insect biodiversity linked to land use and climate change.
The team said that in areas that were subject to low-intensity agriculture but had also seen substantial climate warming, being located close to an area providing natural habitat had helped to buffer the losses.
Where 75 per cent of the land was covered by natural habitat, insect abundance only declined by 7 per cent, compared to a 63 per cent reduction in comparable areas with only 25 per cent covered by natural habitat.
Many insects rely on plants for shade on hot days, so a loss of natural habitat could leave them more vulnerable to a warming climate.
The team also warned that the decline in the insect population may be even greater than their findings suggest, as many areas with long histories of human interference would already have seen biodiversity losses before the start of the study period, and because the study did not account for the effects of other drivers, such as pollution.
Senior author Dr Tim Newbold, also from the research centre at UCL, said: “The environmental harms of high-intensity agriculture present a tricky challenge as we try to keep up with the food demands of a growing population. We have previously found that insect pollinators are particularly vulnerable to agricultural expansion, as they appear to be more than 70 per cent less abundant in high-intensity croplands compared to wild sites.
“Careful management of agricultural areas, such as preserving natural habitats near farmland, may help to ensure that vital insects can still thrive.”
Joint first author Peter McCann, who conducted the research while completing an MSc at the centre, said: “We need to acknowledge how important insects are for the environment as a whole, and for human health and wellbeing, in order to address the threats we pose to them before many species are lost for ever.”
The research is published in the journal Nature.