Species diversity: from global decreases to local increases

Current patterns of global change can strongly affect biodiversity at global, regional and local scales. At global scales, habitat destruction and the introduction of exotic species are contributing to declines in species diversity. At regional and local scales, evidence for declines in diversity is mixed, and recent work suggests that diversity might commonly be increasing. In spite of these trends, considerable research continues to consider explicitly the effects of declines in diversity on processes that operate at regional and local scales (such as ecosystem functioning), without explicitly considering the converse set of questions, namely the effects of increases in diversity. Here, we examine evidence that indicates how species diversity is changing across spatial scales and argue that global decreases in diversity are commonly contrasted by increases in diversity at regional and local scales.