Habitat fragmentation and food security in crop pollination systems
Résumé
Ensuring stable food supplies is a major challenge for the 21st century. There is consensus that increased food production is necessary, but not sufficient, to achieve food security, and that agriculture should also aim at stabilizing crop production over time. In this context, biodiversity-based approaches to food security are increasingly being supported based on the fact that biodiversity can increase and stabilize crop production. However, agricultural systems are often highly fragmented and our current understanding of how such fragmentation affects biodiversity and food production remains incomplete, thus limiting our capacity to manage agricultural landscapes for food security. We developed a spatially explicit model of crop dynamics to investigate how the fragmentation of natural habitats for agricultural conversion impacts food production and food security, with a focus on animal-dependent crop production. Fragmentation produces a variety of spatial and biodiversity-mediated effects that affect both the mean and stability (temporal invariability) of animal-dependent crop production. Fragmentation has a dual effect on animal-dependent production. On the one hand, spatial aggregation of natural land decreases animal-dependent production by reducing the Landscape Pollination Potential, a metric that captures fragmentation and pollinator spillover effects within the agricultural landscape. But aggregation increases animal-dependent production by maintaining a higher pollinator diversity in larger fragments of natural habitat. The net effects of fragmentation on animal-dependent crop production depend on the land-use change pattern, the strength of the pollinator spillover to crop land and the animal pollination dependence of crops. Synthesis. Our study sheds new light in the food security debate by showing that high and stable crop production depends on biodiversity and the spatial fragmentation of agricultural landscapes, and by revealing the ecological mechanisms of food security in crop pollination systems. Management for food security should consider factors such as pollinators’ spillover, the amount and spatial aggregation of semi-natural habitat and the animal pollination dependence of crops. This information would be useful to design agricultural landscapes for high Landscape Pollination Potential. These results are highly relevant in the global change context, and given the worldwide trends in agriculture, which shifts towards more animal-dependent crop production.
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