Maps made more than seventy years ago and records collected by amateur naturalists between the World Wars are providing new clues about declining pollinator numbers, ecologists have found. By showing which land use changes have driven pollinator declines over the past 100 years, the research reveals how we could ensure future land use benefits these vital insects.
The results are presented at INTECOL, the world's largest international ecology meeting, in London this week.
Using newly-developed statistical techniques, the team from Reading, Leeds and the Centre for Hydrology & Ecology analysed two sets of historical data: pollinator data from 1921-1950 based on more than half a million records collected by the Bees, Wasps and Ants Recording Society since 1800 and now digitised; and the Dudley Stamp Land Utilisation survey from the 1930s, the earliest known land use map of Britain.
By comparing this historical data for 21 sites across England with recent pollinator records and land cover maps, they found that 85% of sites had suffered declines in pollinator species richness of between 10 and 50% over the past 80-100 years.
The results show urban landscapes might not be as detrimental to pollinator communities as previously thought; sites with an increased level of urbanisation around them show smaller declines in pollinator diversity. According to Dr Deepa Senapathi of the University of Reading: "This doesn't mean that concrete jungles are good for pollinators, but urban environments may offer diverse forage resources in the shape of people's gardens, parks, churchyards and green spaces which in turn could help support these insects."
This is the first study of its kind to look at the impact of historic land-use change on pollinator communities in Britain. It shows that the dramatic changes in land use since World War II -- in particular agricultural intensification and urbanisation -- have had a significant impact on pollinator communities.
As well as helping explain how past land use change has driven pollinator declines, history offers important lessons about how to improve things in future. "Understanding the major step changes in land utilisation over the last 80-100 years provides a unique understanding of the drivers within changing land-use that might have the most significant impact on pollinator communities," Dr Senapathi says.
In particular, pollinators would benefit from more diverse landscapes. "Based on our results it looks increasingly like sites which were predominantly heathland but are now a combination of heathland, grassland and woodland probably provide a better landscape for pollinators than a landscape with just one habitat type," she explains.
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