COS 77-6 - Resilience and stability in bird guilds across tropical countryside

Wednesday, August 10, 2011: 3:20 PM
10A, Austin Convention Center
Daniel S. Karp, Environmental Science Policy and Management, University of California, Berkeley, Berkeley, CA

Biodiversity is linked to ecosystem services in complex ways, making it difficult to project the consequences of biodiversity loss to humanity. Over recent decades, ecological theory and empirical findings have demonstrated positive relationships between biodiversity and ecosystem services. Therefore, the consequences of biodiversity decline in intensified agricultural landscapes hinge on the resilience of surviving biotic assemblages. We use a ten-year dataset consisting of 2,880 transect censuses of Costa Rican birds to quantify resilience and stability in the face of land-use change. Further, we explain trends in bird resilience and stability by quantifying how birds react to land-use intensification (response diversity) and the frequency with which birds exhibit negative correlations with each other (density compensation). Our land-use gradient extends over four 30km-diameter regions in Costa Rica, within which are replicated sites supporting native forest (n=10), low-intensity land use (n=16), and high-intensity land use (n=15). 


We find that fruit-dispersing, insect-eating, and pollinating guilds were generally resilient to low-intensity land use, but declined significantly with intensification. When compared to forest assemblages, bird abundance, species richness, diversity, and stability declined by an average of 15% in low-intensity land use areas and 50% in high-intensity land use areas. Diverse assemblages were more stable, likely due to the portfolio effect. We find no evidence, however, that density compensation was involved in stabilizing bird guilds over space or time. We conclude that production practices in tropical agricultural landscapes can be fine-tuned to better sustain bird communities and possibly the ecosystem services they provide.

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