Forecasting the potential impacts of CAP-associated land use changes on farmland birds at the national level
Résumé
tThe European Farmland Bird Indicator (FBI) has been adopted as a Structural and Sustainable Develop-ment Indicator by the EU. It identifies farmland bird trends and uses them as a proxy for wider farmlandbiodiversity health. This study analyzed the potential impacts of future Common Agricultural Policy (CAP)land uses on the abundances of the 20 farmland bird species included in the French FBI. Four agricul-tural policy scenarios were studied using the Common Agricultural Policy Regionalized Impact analysis(CAPRI) agricultural model. These four scenarios describe the most likely changes in crop areas and includeregional bird population data from the French Breeding Bird Survey. A habitat association model was usedto predict the potential effects that changes to five crop categories, as well as the total arable area, wouldhave on species indices and the FBI. Our study demonstrates that the relative abundances of specialistfarmland bird species depend on both crop cover type and the total crop area. Model predictions show ageneral decline in the abundance of farmland birds between 2007 and 2020. However, the loss of farmlandbirds is predicted to be less pronounced in the ‘CAP Greening’ scenario, although the predicted FBI valueshave relatively large errors. Moreover, whatever the forecasted CAP, such uniform agricultural changesdo not affect bird populations or the FBI equally across all regions. The FBI’s geographical variability inresponse to applied agricultural changes clearly indicates that a nationwide policy will not yield equalresults but will instead depend on where in the country the agricultural changes occur. To optimize theeffectiveness of the CAP on biodiversity at the national and continental levels, policies should be tested atsmaller spatial levels, such as regions or farmlands, and then, the policies that represent the best optionsfor biodiversity at these sublevels should be combined to create a national plan.