A widespread loss of pollinating insects in recent decades has been revealed by the first national survey in Britain, which scientists say “highlights a fundamental deterioration” in nature.
The analysis of 353 wild bee and hoverfly species found the insects have been lost from a quarter of the places they were found in 1980. A third of the species now occupy smaller ranges, with just one in 10 expanding their extent, and the average number of species found in a square kilometre fell by 11.
A small group of 22 bee species known to be important in pollinating crops such as oilseed rape saw a rise in range, potentially due to farmers increasingly planting wild flowers around fields. However, the scientists found “severe” declines in other bee species from 2007, coinciding with the introduction of a widely used neonicotinoid insecticide, which has since been banned.
Researchers have become increasingly concerned about dramatic drops in populations of insects, which underpin much of nature. Some warned in February that these falls threaten a “catastrophic collapse of nature’s ecosystems”, while studies from Germany and Puerto Rico have shown plunging numbers in the last 25 to 35 years.Advertisement
The study, published in the journal Nature Communications, is based on more than 700,000 sightings made by volunteers across Britain from 1980 to 2013. These are used to map the range of each species of bee and hoverfly over time. The data did not allow the assessment of numbers of insects, but some researchers think populations have fallen faster than range.
Pollinating insects are vital to human food security, as three-quarters of crops depend on them. They are also crucial to other wildlife, both as food and as pollinators of wild plants. “The declines in Britain can be viewed as a warning about the health of our countryside,” said Gary Powney at the Centre for Ecology and Hydrology in Wallingford, who led the research.
He called for more volunteers to take part in the UK Pollinator Monitoring Scheme: “Their contribution is vital for us to understand what is happening in our landscape.” Another recent study found that allotments, weedy corners and fancy gardens can all be urban havens for bees.
The biggest factor in the decline in pollinators is likely to be the destruction of wild habitats and use of pesticides as farming has intensified. But the analysis also revealed a particularly big drop of 55% in the range of upland bee and hoverfly species, and significant falls in northern Britain, which may result from climate change making conditions too warm.
Among the bees whose range has shrunk are the formerly widespread red-shanked carder bee, whose extent fell by 42%, and the large shaggy bee, whose range fell 53%. But the lobe-spurred furrow bee, which was once rare, has expanded its range fivefold and is now considered an important crop pollinator in England.
Powney said the increased range of the bees most commonly pollinating crops is good news and might be a result of more oilseed rape being grown, as well as wildflower margins being planted. But he also warned: “They are a relatively small group of species. Therefore, with species having declined overall, it would be risky to rely on this group to support the long-term food security for our country. If anything happens to them in the future there will be fewer other species to ‘step up’.”
Prof Dave Goulson, at the University of Sussex and not part of the latest research, said: “Previous studies have described declines in UK butterflies, moths, carabid beetles, bees and hoverflies – this new study confirms that declines in insects are ongoing.”
If the losses of upland and northern species are due to climate change, “then we can expect far more rapid declines of these species in the future, as climate change has barely got started”, he said. Goulson also said the start of more rapid declines in southern bees after 2007 coincided with the first use of now-banned neonicotinoid pesticides.
Roy van Grunsven, at the Dutch Butterfly Conservation project, said the decline in numbers of insects was very likely to be a lot higher than the shrinking of their range: “Going from flowery meadows full of bees to intensive agriculture with a few individuals in a road verge does not result in a change in distribution, but of course is a huge change in [numbers].”
Matt Shardlow, of the conservation charity Buglife, said unless the pesticide approval process was improved to help bee safety and green subsidies were targeted to create corridors that connect wild spaces, we can expect the declines to continue or worsen.
by Damian Carrington, Environment editor, The Guardian