Reply to Carnicer et al.: Environmental heterogeneity reduces breeding bird richness in Catalonia by increasing extinction rates

The area-heterogeneity tradeoff (AHTO) implies that increasing environmental heterogeneity reduces the amount of effective area available for individual species (ref. 1 and Fig. 1). Theoretical models show that this tradeoff leads to a positive effect of heterogeneity on extinction rates and a unimodal effect on species richness (1–3). Our analysis of bird distribution in Catalonia using altitude range as a measure of heterogeneity (3) was consistent with both predictions.