Efeitos da perda e fragmentação de habitat sobre a biodiversidade: uma busca por padrões, mecanismos e modelos aplicados à conservação

Abstract

The biodiversity crisis is alarming, with a global loss os over half of the species populations between 1970 and 2018. One of the main causes of this crisis is considered to be combined processes of habitat loss and fragmentation. Hypotheses such as the Habitat Amount Hypothesis (HAH), the existence of thresholds in the response of biological communities to habitat loss, and the SLOSS ("single large or several small") debate have been developed to better understand landscapes. Although solving these hypoteses is urgent for conservation, they have not yet been fully elucidated. The main object of this work is to investigate the effects of habitat loss and fragmentation on biodiversity in a search for patterns, explanatory mechanisms and, ultimately, models applied to conservation. Working on each of theses hypotheses previously mentioned, we structured this thesis as follows: Chapter 1) an extensive global analytical synthesis that quantifies the variation os species richness in response to habitat amount at that landscape scale; Chapter 2) a case study that proposes applying the patterns detected in Chapter 1 to global Protected Areas (PAs) that suffered an enacted reduction in their original area in recent decades due to legal changes applied to PAs; Chapter 3) to understand the methodological challenges related to the SLOSS debate. Our results indicate that: i)there is indeed a general positive efect of habitat amount on species richness across global commuinities, but a lot of variability of these effect is detected between communities and landscapes; ii) although with a restrictive applicability, working with a habitat amount threshold of 30%is a good first step toward species conservation; iii) there may be an average loss of 394 vertebrates species per PA that suffered an enacted reduction in its ariginal area, with an increasing vulneralbility os vertebrates in PAs in tropical regions due to activities with a high modifying impact on the landscape; iv) sampling bias at the spatial distibuction of species richness in a landscape have a decisive influence on maximizing biodiversity within the SLOSS debate. We hope to support decision makers more decisively with these results, contributing to major global agendas for the protection of species and ecosystems actually reaching their proposed objectives.