Effects of Habitat Fragmentation on Biodiversity

TLDR

The literature on habitat fragmentation is extensive and heterogeneous, with fragmentation commonly defined as a landscape‑scale process that includes both habitat loss and the breaking apart of habitat, yet empirical studies often conflate these components, making interpretation difficult. The study aims to disentangle the independent effects of habitat loss and fragmentation per se on biodiversity and to clarify the terminology by reserving “fragmentation” for the breaking apart of habitat. The authors propose an analytical framework that separately quantifies habitat loss and fragmentation per se to assess their distinct impacts on biodiversity. Empirical evidence indicates that habitat loss consistently reduces biodiversity, whereas fragmentation per se has weaker, mixed effects that can be either positive or negative.

Abstract

▪ Abstract The literature on effects of habitat fragmentation on biodiversity is huge. It is also very diverse, with different authors measuring fragmentation in different ways and, as a consequence, drawing different conclusions regarding both the magnitude and direction of its effects. Habitat fragmentation is usually defined as a landscape-scale process involving both habitat loss and the breaking apart of habitat. Results of empirical studies of habitat fragmentation are often difficult to interpret because (a) many researchers measure fragmentation at the patch scale, not the landscape scale and (b) most researchers measure fragmentation in ways that do not distinguish between habitat loss and habitat fragmentation per se, i.e., the breaking apart of habitat after controlling for habitat loss. Empirical studies to date suggest that habitat loss has large, consistently negative effects on biodiversity. Habitat fragmentation per se has much weaker effects on biodiversity that are at least as likely to be positive as negative. Therefore, to correctly interpret the influence of habitat fragmentation on biodiversity, the effects of these two components of fragmentation must be measured independently. More studies of the independent effects of habitat loss and fragmentation per se are needed to determine the factors that lead to positive versus negative effects of fragmentation per se. I suggest that the term “fragmentation” should be reserved for the breaking apart of habitat, independent of habitat loss.