Agricultural land occupies around 38% of the planet’s land surface and the spread and intensification of agriculture are recognised as two of the most important global threats to wildlife. In developing countries, rapidly increasing human populations and per capita diet expectations are requiring ever increasing food production and there is a growing need to manage the agricultural footprint.
Agriculture impacts on biodiversity in two main ways: (i) through the clearance of pristine habitats for new planting or (ii) through the intensification of existing systems, resulting in increased yields per unit area. Several lines of evidence suggest that farming is changing and impacting on biodiversity faster in the developing than the developed world. Two possible solutions have been suggested: wildlife friendly farming (land sharing) - low intensity or extensive agriculture, supporting lower yields but higher levels of biodiversity and land sparing - areas are set aside for nature conservation and the remaining land farmed intensively with higher yields.
The choice, therefore, is between having a greater area of lower-yielding wildlife friendly farmland and less pristine habitat or having a smaller area of high yielding less wildlife friendly farmland and more area available for wild nature.
Rhys Green et al. (Science, 2005) constructed a theoretical model relating the population density of individual bird species to the yield per unit area of farmland. The way in which species density changes with increases in crop yield is key in determining whether a particular farming regime increases or decreases populations. Few studies have measured how population density changes across a range of production regimes; fewer still have simultaneously measured agricultural yields.
It is this crucial gap in knowledge that this project will address. By drawing on three existing data sets, relating to density of birds in farmland and forest and agricultural yields in the same area, this project will assess whether the impacts of agricultural intensification on biodiversity can be ameliorated by having larger areas of low-intensity farming (land sharing), or by intensifying existing farmland in order to preserve pristine habitats (land sparing).
This project was funded by the CCI Collaborative Fund for Conservation.