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Bug’s Life: the demise of insects

Overall insect population numbers have shrunk by 40 per cent over the last four decades Overall insect population numbers have shrunk by 40 per cent over the last four decades Nobra
08 Jul
2017
It’s not just the bees that are disappearing. Insects across the board are showing dramatic drops in population levels, leading to a serious knock-on effect for ecosystems everywhere

To date, experiences of insect declines have largely been anecdotal. Many people recall wiping more bugs off car windshields in the past, or remember seeing more of recognisable species like ladybirds, butterflies and bumblebees. Now, an increasing number of scientific studies are beginning to support these observations.

Last year, US beekeepers reported a 44 per cent collapse to their colonies during the winter months. In the same time period, the UK butterfly monitoring scheme reported reductions across 70 per cent of all species. As for the wider insect world, all insect and invertebrate populations were calculated to have shrunk by 45 per cent in the last four decades, according to biologist Rodolfo Dirzo in his seminal paper ‘Defaunation in the Anthropocene’.Recent research carried out in Krefeld, a western German state of North Rhine-Westphalia, saw ‘an 80 per cent decline in flying insect biomass in the last 25 years,’ says Professor Dave Goulson, biologist at the University of Sussex. He helped to analyse the German data, whose numbers ‘were the most dramatic to date’.

Goulson, who often studies UK bees, believes pesticides are partly to blame. Only tiny doses of neonicotinoids, a relatively new but widespread group of pesticides, are enough to paralyse and kill bees (just 4 billionths of a gram) and his research has found that even smaller doses leave them confused, unable to navigate and unable to collect food. ‘Nobody knows for sure the cause of the declines in all insects,’ he says, ‘but most would agree that it is a combination of pesticide use and habitat loss.’

Specific extinctions have also contributed to the thinning numbers, and 42 per cent of bugs on the IUCN’s Red List are categorised as being under threat. ‘However, in many ways the loss of bioabundance is perhaps more significant,’ argues Goulson. ‘If flying insect populations are down by as much as 80 per cent, that means far fewer pollinators and far less food for insect-eating animals such as bats and birds.’

This was published in the July 2017 edition of Geographical magazine.

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