Mudanças climáticas e pequenos mamíferos não-voadores na Caatinga: impactos na distribuição e estratégias de conservação

Abstract

Climate change is threatening biodiversity and the functioning of ecosystems. They are especially worrying in arid and semi-arid regions of the world, such as the Caatinga, as they have caused a reduction in precipitation and an increase in temperature in these areas, which already face a large water deficit. The Caatinga is an exclusively Brazilian biome and the largest and most biodiverse Seasonal Dry Tropical Forest in the world. However, this dry forest has numerous knowledge gaps, and it is the biome with the least information on mammals. Therefore, this thesis began by compiling a dataset of records of small non-flying mammals for the biome, prioritising species with vouchers held in scientific collections, and seeking to guarantee the accuracy of the geographical coordinates. The dataset gathered a total of 3133 records from 816 localities, resulting in a richness of 47 native species (12 marsupials and 35 rodents), as well as three exotic rodents (Rattus rattus, Rattus norvegicus and Mus musculus). Three new species are also reported for the biome and its transition areas: the rodents Calomys mattevii, Holochilus oxe and Nectomys squamipes. In addition to richness and composition, the dataset contains biometric data for many records. Having surveyed the species and their points of occurrence in the biome, we sought to identify climatically suitable areas for each of them in the Caatinga and where these areas would be considering two climate change scenarios (SSP 245 and 585) and for the years 2050 and 2070. Ecological Niche Modelling was used to obtain projections for 24 species of rodents and marsupials. By quantifying how much climatically suitable area would be lost or gained in each of the scenarios and years, it was found that among the arid adapted species, only four rodents should gain climatically suitable area, while the other species would lose. As for the noarid adapted species, i.e. those that are more common in areas influenced by the Atlantic Forest, would be more vulnerable to climate change, with a large reduction in their climatically suitable areas in the Caatinga. Once these variations in climate suitability for species had been identified, spatial prioritisations were then carried out in order to identify priority areas for preserving small mammal species in the Caatinga in the present time and in the future of climate change, using Zonation software. The prioritisations presented here take into account the future of climate change and present a low risk of implementation, and can be considered as a "no regrets" conservation action. By verifying that these priority areas are poorly supported by the current National System of Conservation Units, cost-effective strategies were defined for expanding protected areas in the Caatinga, especially by transforming certain Sustainable Use areas into Integral Protection. The results presented here, especially the reduction in climatically suitable areas for the majority of small mammal species in the Caatinga, reinforce the need to ensure that conservation strategies are in place to deal with the unavoidable climate change consequences in this unique biome.