Heterogeneity and the trade-off between ecological and productive functions of agro-landscapes: A model of cattle-bird interactions in a grassland agroecosystem

There is empirical evidence that the proportions of different land uses or management regimes and their spatial arrangements can affect the long-term dynamics of bird species in agro-landscapes. The aim of our study was to assess the extent to which biodiversity can be enhanced by altering landscape structure without reducing agricultural production. We focused on a wader bird, the Northern Lapwing (Vanellus vanellus), in grassland landscapes in the Marais Poitevin area (France). For the purposes of our study, we developed a spatially explicit, dynamic model linking grass dynamics in grazed and mowed fields to lapwing population dynamics on a landscape scale. We then computed contrasting landscapes composed of fields with different management regimes that compensated for or complemented each other. The mechanism of compensation corresponded to the case where one management regime is favorable to a species, and the other is less so. The mechanism of complementation corresponded to the case where each of two management regimes is partially favorable to a species. Our results showed that the relative share of different management regimes was the main driver of Northern Lapwing dynamics in landscapes characterized by compensatory management regimes. In landscapes characterized by complementary management regimes, the spatial arrangement of the management regimes was also an important, albeit secondary, driver of bird population dynamics. Managing the spatial arrangement of management regimes is a way to improve the trade-off between ecological and agricultural performances on a landscape scale by improving ecological performances without altering the level of production. Landscape heterogeneity appears to be a promising way to reconcile the agricultural and ecological functions of agriculture, although it raises several issues concerning collective management.