Evaluating temporal turnover in avian species richness in a Mediterranean semiarid region: different responses to elevation and forest cover

Abstract

Aim: When studying the effects of global change on biodiversity, it is far more common for the effects of climate change and land-use changes to be assessed separately rather than jointly. However, the effects of land-use changes in recent decades on species richness in areas affected by climate change have been less studied. We assess the temporal turnover in species richness of an avian community between a historical period and a modern one as a consequence of global change. Location: Semiarid Mediterranean ecosystem (southeastern Spain). Method: We fitted a hierarchical multispecies occupancy model for each period (1991–1992, and 2012–2017), obtaining avian species-specific estimates of occupancy probability in relation to environmental covariates (elevation and forest cover). We analyse the relationships between changes in the bird community and environmental variables, analysing the temporal turnover of the species richness and the richnessbased species-exchange ratio. Results: The estimated species richness accounting for detectability was higher than observed species richness, and decreased in the more recent period. Following our hypotheses, we observed a dual pattern of species richness increase associated with different elevations, showing different species turnover rates due to the joint effects of climate change and land-use change. There is a trend towards greater species richness with higher elevations that is associated with climate change, where the species turnover rate is low. Also, species richness increased towards lower elevations, but with a high turnover rate. The latter can be due to species expansions throughout new habitat configurations in bordering forest systems associated with anthropic land-use changes. Conclusions: Our study is of great interest to understand the temporal turnover of avian species richness associated with areas experiencing both climate and land-use change