Agricultural landscapes with high compositional heterogeneity support both forest and farmland birds in Taiwan

Abstract

Promoting heterogeneous agricultural landscapes could help to reduce the negative impacts of habitat conversion on biota. However, the benefits of landscape heterogeneity can vary among spatial scales and taxa. To design biodiversity-friendly landscapes, we use nationwide bird survey data and land use maps to examine the effects of compositional heterogeneity, configurational heterogeneity, and habitat amount at different scales on the species richness of different bird groups. We examine the effects of configurational heterogeneity (measured using edge density), compositional heterogeneity (Shannon's diversity index of habitat types), and habitat amount (proportion of forest and farmland cover) at both transect (local) and landscape (0.5, 1, or 2 km) scales on the species richness of all breeding birds, forest birds, farmland birds, and introduced birds. Total species richness had a hump-shaped relationship with local forest cover, and with farmland cover at landscape scale. Richness of both forest birds and richness of farmland birds increased with Shannon's diversity index of habitat types at both local and landscape scales, but only increased with the amount of their preferred habitat at the local scale. Richness of introduced birds was greater in landscapes with higher edge density, suggesting those species are associated with human-dominated landscapes. High compositional heterogeneity with low configurational heterogeneity at the landscape scale may help maintain native bird richness while minimising the spread of introduced species in Taiwan. These results can help guide land use planning to achieving biodiversity goals in a country with intensive land-use competition.