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.

Aim: To test whether the occupancy of shorebirds has changed in the eastern Canadian Arctic, and whether these changes could indicate that shorebird distributions are shifting in response to long-term climate change Location: Foxe Basin and Rasmussen Lowlands, Nunavut, Canada Methods: We used a unique set of observations, made 25 years apart, using general linear models to test if there was a relationship between changes in shorebird species’ occupancy and their Species Temperature Index, a simple version of a species climate envelope. Results: Changes in occupancy and density varied widely across species, with some increasing and some decreasing. This is despite that overall population trends are known to be negative for all of these species, based on surveys during migration. The changes in occupancy that we observed were positively related to the Species Temperature Index, such that the warmer-breeding species appear to be moving into these regions, while colder-breeding species appear to be shifting out of the regions, likely northwards. Main Conclusions: Our results suggest that we should be concerned about declining breeding habitat availability for bird species whose current breeding ranges are centred on higher and colder latitudes.

In biodiversity conservation, the “SL > SS principle” that a single (or few) large habitat patches (SL) conserve more species than several small patches (SS) is used to prioritize protection of large patches while down-weighting small ones. However, empirical support for this principle is lacking; most studies find SS > SL. We propose a research agenda to resolve this dilemma by asking, “are there consistent, empirically-demonstrated conditions leading to SL > SS?” We develop a hypothesis to answer this question, the “SLOSS cube hypothesis,” which predicts SL > SS only when all three of the following are true: between-patch movement is low, population dynamics are not influenced by spreading-of-risk, and large-scale across-habitat heterogeneity is low. We then propose methods to test this prediction. Many tests are needed, comparing gamma diversity across multiple landscapes varying in number and sizes of patches. If the prediction is not generally supported across tests, then either the mechanisms leading to SL > SS are extremely rare in nature, or they are outweighed by countervailing mechanisms leading to SS > SL (e.g. lower competition or higher immigration in SS), or both. In that case, the SL > SS principle should be abandoned.