Bees and wasps are in decline worldwide. The potential reasons are several and they may occur in combination, including the indiscriminate use of pesticides, changes to climate and habitat, parasitic infection and mite infection.
A new study, conducted in England, has considered whether changing land use leads to pollinator declines. For this, the study used longer-term historical data relating to changing land applications and insect numbers. The two sets of data were correlated.
For this meta-study, researchers began assembling data from the 1930s and carried on to the present day. Here scientists considered land-cover changes within each locale, and the surrounding landscape at a range of 1, to 10 kilometers. In each area they considered the estimated numbers of bee and wasp communities and species.
The studies found that the history of land provided an explanation for alterations to the numbers of bee and wasp communities. In most cases, land use had altered and this had led to a decline in insect numbers over an 80 year period.
Interestingly, areas close to intensive crop farming expansion produced the biggest declines bee and wasp species. Intensive farming practices include growing high-yield crops, using fertilizers and pesticides. The inference was that agricultural intensification, particularly with fields growing only one type of crop, reduced the greatest numbers of insect pollinators. This is thought to be because bees and wasps will have lower opportunities to forage in flowering crops. In contrast, areas where urban expansion had occurred produced the smaller losses.
The solution, the biological researchers argue, is to create a mixed landscape, such as woodland, heathland and grassland, to offer bees and wasps greater foraging and nesting opportunities.
The issue of promoting bees and wasps is of importance because these insects are the primary pollinators of wild plants and crops. It estimated that over three quarters of the world’s most important crops, like oilseed rape, apples and strawberries, are reliant upon bees and wasps for pollination.
The research has been published in the journal Proceedings of the Royal Society B, in a paper called “The impact of over 80 years of land cover changes on bee and wasp pollinator communities in England.”
