Many of the likely causes of pollinator decline are linked to land use changes over the last few decades. Agricultural intensification has seen a decrease in traditional farming practices and farmland features such as hedgerows, set-aside land and flower-rich meadows, and an increase in practices that are likely to be less ecologically benign. However, the strength of the link between changes in both land use and pollinator communities is relatively unknown. Information on this link is important for developing strategies to mitigate pollinator losses without jeopardising agricultural production or the livelihood of land owners and managers.
The strongest evidence of these links will come from the “accidental experiments” of land use change, and there are two main objectives to this part of the project that will make use of them. Firstly, there are a number of datasets that report recent pollinator dynamics over a range of landscapes that have historically changed to varying degrees (A1, below). Secondly, there are a number of landscapes that have changed dramatically in the last 50 years, and for which historical pollinator surveys are available (A2, below). By conducting re-surveys in these areas, it will be possible to test if pollinator communities have changed in the most altered landscapes. Thus, two complementary approaches will provide comprehensive evidence of the link between shifts in land use and pollinators.
A1: Land cover change in areas of contrasting pollinator dynamics. Historical data summarised in the work by Biesmeijer et al. (2006) can be used to identify 10 x 10 km areas which have seen increases and decreases in pollinator diversity since 1980. In addition, the change in land use in the same areas over the same period can be inferred by changes in the cover of different land classes, estimated from satelite imagery by CEH. By analysing these two datasets together, we can find out if and how land use affects pollinator changes.
A2: Pollinator change in areas with contrasting land use histories. For this objective, a contrary but complimentary approach will be taken. We have compiled a dataset of 36 historical studies of pollinator densities between the 1870s and 1970s. Many of the sites included in these studies have undergone extensive changes in land use, providing an excellent opportunity to re-survey pollinators and compare the findings to the historical data. This will allow the examination of pollinator diversity and density as a function of land use change.
Biesmeijer, J.C., et al. 2006. Parallel declines in pollinators and insect-pollinated plants in Britain and the Netherlands. Science 313: 351-354