Alpha, beta and gamma diversity in relatively natural, mixed and transformed landscape scenarios

Biodiversity losses and biotic homogenisation associated with human-induced land-cover changes are key issues for ecology. However, the effects of human-caused land-use changes on biodiversity change at the landscape scale are not well understood. Combining the PREDICTS global biodiversity database with MODIS satellite-based land cover from 2001 to 2013, we created three landscape modification scenarios - relatively natural, partially modified (mixed, e.g., mixtures of crops and natural remnants) and fully modified (transformed, e.g., urban and plantation mosaics) and estimated the landscape-scale alpha, beta and gamma diversity associated with each. Our results reveal that landscape-scale modification from relatively natural landscapes to mixed landscapes increases the variety of ecosystem types and modification levels, hence increasing the variety of ecological communities (beta diversity) and maintaining landscape-level diversity (gamma), despite reductions in average local-level diversity (alpha). However, total transformation (from mixed towards completely transformed landscapes) causes a decline in both alpha and gamma diversity. Our results highlight that anthropogenic modification can potentially increase some elements of biodiversity while decreasing others and that high levels of landscape-scale diversity can be maintained within mixed landscapes.