Patch-scale edge effects do not predict landscape-scale fragmentation effects

Negative patch-scale edge effects, where species are more common in habitat interior than edge, are often used as evidence of negative fragmentation effects. This is because, for a given total habitat area, a more fragmented landscape contains less interior habitat. I tested this cross-scale extrapolation by extracting from the literature a sample of species showing negative or positive landscape-scale fragmentation effects, and then for each species I searched for studies from which I could calculated the slope of its patch-scale edge effect. Species showing negative patch-scale edge effects were equally likely to show negative or positive landscape-scale fragmentation effects, and likewise for species showing positive patch-scale edge effects. Thus, a species' patch-scale edge effect does reliably predict its response to habitat fragmentation. Fragmentation effects, and the efficacy of policies related to them, require evidence at a landscape scale, comparing species' responses across landscapes with different levels of fragmentation.