The first national survey of pollinating insects across Great Britain has revealed that a third of wild bee and hoverfly species are in decline, which scientists say “highlights a fundamental deterioration” in nature.
The study, published in the journal Nature Communications, is based on biological records made by volunteers across Britain from 1980 to 2013. These records were used to map the range of 353 species of bee and hoverfly over time. The analysis of 700,000 records of wild bees and hoverflies found that approximately 33% of the 353 species studied declined in the extent of their range since 1980. Overall, pollinating insects have been lost from a quarter of the places they were found in just a few decades. In addition, one third of the species included in the study now occupy smaller ranges, with the average number of species found in a square kilometre falling by 11.
The assessment found that a small group of 22 wild bee and hoverfly species known to be important in crop pollination have been doing relatively well, increasing their range between 1980 and 2013. This suggests that agri-environment schemes, where farmers sow wild flowers around fields, are having a positive impact. However, the scientists found “severe” declines in other bee species from 2007, four years after the introduction of a group of widely used pesticides known as neonicotinoids, which have since been almost entirely banned by the EU.
By pollinating wild plants and providing a crucial food source for other wildlife, invertebrates underpin the worlds ecosystems. Scientists have therefore become increasingly concerned about the dramatic population declines that have been highlighted in recently published studies. In February, a global review of long-term scientific surveys of insects warned of a “catastrophic collapse of nature’s ecosystems”, while recent studies from Germany and Puerto Rico have highlighted worrying declines in abundance over the past few decades.
Pollinating insects are also vital to human food security. Three-quarters of all the different types of crops that humans grow around the world depend on them. While it is recognised that current standard economic indicators, such as Gross Domestic Product, inadequately capture the range of ecosystem services provided by pollinators, the market value of the global crop pollination service that they provide has recently been estimated as being worth US$235-577 billion annually. In the UK alone, insects pollinate £690 million worth of crops each year.
Gary Powney at the Centre for Ecology and Hydrology in Wallingford, who led the research, commented:
“The declines in Britain can be viewed as a warning about the health of our countryside.”
He called for more volunteers to take part in the UK Pollinator Monitoring Scheme to help us to better understand what is happening in our landscape.
The biggest factors driving the observed declines in pollinating insects are the loss of high-quality flower-rich habitats and the use of pesticides as farming has intensified.
The analysis also revealed significant declines in upland bee and hoverfly species, as well as significant losses in northern Britain, with climate change thought to be responsible.
Among the biggest losers whose range have shrunk are the once widespread red-shanked carder bee Bombus ruderarius, whose extent fell by 42%, and the large shaggy bee Panurgus banksianus, whose range fell 53%. By contrast, the ashy mining bee Andrena cineraria and the lobe-spurred furrow bee Lasioglossum pauxillum, have increased their range fivefold.
Professor Dave Goulson of the University of Sussex, who was not involved with the study, commented:
“Previous studies have described declines in UK butterflies, moths, carabid beetles, bees and hoverflies. If further evidence were needed, this new study confirms that declines in insects are ongoing.”
If the observed declines in upland and northern species are a result of 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.
The data did not allow the assessment of numbers of insects, but some researchers think it likely that abundance will have declined even faster than ranges have shrunk. This is likely, as a shift from flower-rich habitats full of pollinators to intensive agriculture where these insects can only find the resources they need in the remaining road verges would not necessarily result in a change in distribution, but would very likely result in huge changes in abundance.
In order to address this biodiversity disaster, Matt Shardlow, chief executive of the invertebrate conservation charity Buglife, is calling for significant improvements to the pesticide approval process, as well as green subsidies targeted to create corridors that connect wild spaces.
