Relative effects of habitat loss and fragmentation on population extinction

In their review of the recent ''explosion of spatially explicit theory'' in ecology Kareiva and Wennergren (1995) suggest a number of emerging principles for species conservation. One of these principles is that how habitats are arranged in space can mitigate the risks of species extinctions from habitat loss. I tested this by estimating the relative importance of habitat loss and habitat spatial pattern (fragmentation) on population extinction, using a simple, spatially explicit simulation model. Results indicate that the effects of habitat loss far outweigh the effects of habitat fragmentation. I therefore suggest that, in fact, details of how habitats are arranged cannot usually mitigate the risks of habitat loss. Conservation efforts should be aimed foremost at stopping habitat loss and at habitat restoration.