Efeitos da quantidade de habitat na comunidade de aves na Mata Atlântica

Abstract

Several studies warn of the impacts of habitat loss and fragmentation on biodiversity and ecological processes, with implications for the conservation of species and ecosystems. However, in the last decade, researchers have raised questions about how such impacts have been measured and about the positive or negative nature of these impacts on different taxonomic groups. This study evaluated the effects of habitat loss and fragmentation on parameters of bird communities, such as richness and composition of species, structure of functional groups, proportion of endemisms and occurrence of threatened species, in 30 landscapes inserted in the biogeographic domain of the Atlantic Forest in the southeastern Brazil. For this purpose, a multiscale approach was adopted, delimiting buffers of 1,000, 2,000 and 3,000m from a central point in each landscape, within which metrics were collected for environmental variables (habitat amount, percentage of core habitat area, focal fragment area, structural connectivity and functional connectivity). Avifauna sampling was carried out from listening and observation points in the center of each landscape, conducted over the spring and summer, between October 2018 and March 2019. The effects of environmental variables on the parameters of the communities were tested through generalized linear models (GLM) and distance-based linear models (DistLM). In total, 271 species were recorded, of which 181 are forest specialists, and 108 endemisms, representing 31% of the endemic taxa of the Atlantic Forest. Nine species are at risk of extinction at the state, national or global level, eight of which are endemic to the Atlantic Forest. The variation in the general species richness and in the richness of forest specialists was positively influenced by the percentage of available core habitat area, with the greatest effect observed on the 3,000m spatial scale. The variation in species composition was mainly explained by the altitude and the amount of available forest habitat on the 3,000m scale. The proportion of endemic taxa of the Atlantic Forest in the communities was strongly influenced by the amount of available habitat and functional connectivity, with the most intense effects being observed on the 2,000m spatial scale, demonstrating greater vulnerability of these species to deforestation. The functional groups showed different responses to the environmental variables, with seed dispersers and invertebrate predators more sensitive to habitat loss, while pollinators and vertebrate predators were apparently unaffected by any variable. The structure of the functional groups remained stable, even in the most fragmented landscapes and with a small amount of habitat, indicating that the species that persist in these areas are still capable of maintaining ecological functions, which has positive implications for the resilience of these forest environments. This findings offer strong evidence that habitat loss has a significant impact on Atlantic Forest avifauna and reinforce the need to preserve the large forest fragments remaining in the southeast Brazils landscapes.