Isolation determines patterns of species presence in highly fragmented landscapes

Abstract

In fragmented landscapes, changes in habitat availability, patch size, shape and isolation may affect survival of local populations. Proposing efficient conservation strategies for such species relies initially on distinguishing the particular effects of those factors. To address these issues, we investigated the occurrence of 3 bird species in fragmented Brazilian Atlantic Forest landscapes. Playback techniques were used to collect presence/absence data of these species inside 80 forest patches, and incidence models were used to infer their occupancy pattern from landscape spatial structure. The relative importance of patch size, shape and surrounding forest cover and isolation was assessed using a model selection approach based on maximum likelihood estimation. The presence of all species was in general positively affected by the amount of surrounding habitat and negatively affected by inter‐patch distances. The joint effects of patch size and the surrounding landscape characteristics were important determinants of occupancy for two species. The third species was affected only by forest cover and mean patch isolation. Our results suggest that local species presence is in general more influenced by the isolation from surrounding forests than by patch size alone. We found evidence that, in highly fragmented landscapes, birds that can not find patches large enough to settle may be able to overcome short distances through the matrix and include several nearby patches within their home‐ranges to complement their resource needs. In these cases, patches must be defined as functionally connected habitat networks rather than mere continuous forest segments. Bird conservation strategies in the Atlantic forest should focus on increasing patch density and connectivity, in order to implement forest networks that reduce the functional isolation between large remnants with remaining core habitat.

Responses of bees to habitat loss in fragmented landscapes of Brazilian Atlantic Rainforest

“…Therefore, approaches that consider both local forests as well as the whole regional set of patches as the sampling units (i.e. the landscapes) tend to provide better insights on the effects of landscape change on biological populations and communities (Boscolo and Metzger 2011). Recent habitat fragmentation research showed the possibility of buffering effects among scales, regulating the biotic responses to landscape structure in a top-bottom system (see, Pardini et al 2010).…”

“…Such narrow-ranging studies may miss landscape effects which are only detectable at wider scales. Since single patches within highly fragmented landscapes will hardly support viable populations on their own (Boscolo and Metzger 2011). Ignoring the influence of the quantity or quality of surrounding habitat can compromise the understanding of regional extinction processes.…”

Atlantic Forest Fragmentation Analysis and Landscape Restoration Management Scenarios

“…We recommend vegetation rearrangement to enlarge the smaller patches and enhance their core areas and to patches (Boscolo & Metzger 2011), therefore ensuring a more permeable landscape (Ribeiro et al 2009). If patches smaller than 10 ha were removed from the study landscape, approximately 90% of the remaining patches would be lost.…”

“…In comparison to Boscolo & Metzger (2011) the mean patch isolation value was low. The former authors showed that less forested landscapes present higher mean isolation when compared to more forested ones.…”

Anchor Areas to Improve Conservation and Increase Connectivity within the Brazilian Mesopotamia of Biodiversity

“…Besides, these fragments are important elements for maintaining connectivity within each sub-region, since their removal would result in the break-up of the largest sub-graphs (Saura & Pascual-Hortal 2007). The conservation of these fragments (e.g., as private reserves) would be essential to maintain the flux of organisms in the landscape, reducing the isolation of larger fragments (Boscolo & Metzger, 2011).…”