Does agroforestry conserve trees? A comparison of tree species diversity between farmland and forest in mid-hills of central Himalaya
The expansion and intensification of agriculture is a major driver of forest shrinkage and biodiversity loss, and the threat to biodiversity is projected to increase with increased population growth and food demand; therefore, food production with a minimal ecological footprint is an important development goal. Agroforestry, as practiced in the hilly populated agricultural landscape of the central Himalaya, reflects a scenario of land sharing with a balance in the trade-offs between forest management and tree protection/retention in private farmlands. We aim to assess whether agroforestry has contributed to conserving tree species diversity. We compare different measures of tree species diversity and trends in richness with elevation between farmland and forest using empirical data gathered from 1000 to 1800 masl in the mid-hills of central Nepal. We find that farmlands are consistently richer in tree species than forest. Our analysis further reveals that in spite of many shared species between forest and farmland they are different in composition, due to differences in the relative abundance of shared species and the presence of unique species in each land use types. We shed light on the ecological and management-related drivers that enhance tree species richness in the populated farmlands. We highlight that an agricultural landscape can complement, but not necessarily substitute, the biodiversity conservation goal of protected areas by providing alternative habitats, refugia and landscape connectivity for floral and faunal species. We underscore that biodiversity conservation strategies and landscape planning should acknowledge the role of agroforestry in maintaining trees and associated biodiversity, and provisioning ecosystem services.