Cobertura florestal e defaunação na Caatinga, o maior núcleo de floresta sazonalmente seca da América do Sul

Abstract

Pleistocene climatic fluctuations contributed to the great extinction of the megafauna, but the presence of human beings at the time accelerated the contribution of this great extinction. Many of these animals were herbivores and contributed to ecological functions, amongst them, mutualistic relationships. These animals acted out as seed dispersers, allowing plant species to remain in different regions and contributing to the composition vegetation formations. In the Caatinga domain, activities in the Anthropocene such as hunting and livestook raising have been causing a loss in the diversity of species of medium and large mammals, as the case of the tapir (Tapirus terrestre) is currently extinct in the region, in addition to loss of plant diversity. The loss of these diversities affects ecological interactions such as seed dispersal and carbon storage. To understand how anthropization has interfered in the Caatinga, we did 1) we reconstruct distribution models of forest vegetation and open vegetation in the domain by the MaxEnt algorithm evaluating effects of soil type and Quaternary climate variations, based on the distribution of forest birds and fossils of the megafauna. We found that the region exhibited areas of climate and soil capable of supporting more forest cover than currently exists, with only 4.34% of this vegetation type; 2) we verified the prediction of defaunation and the downsizing effect caused by it using the MaxEnt algorithm and the spatial distribution of lost species, as well as the underlying factors that contribute to their decline by the Random Forest algorithm. We found a drastic defaunation, with ~80% of species extinct locally, supporting the downsizing effect, with hunting being the main indicator for this decline; and 3) we verified the relation between with carbon removal and aboveground biomass, the relation richness of medium and large frugivorous mammals and defaunation with carbon removal, generated by generalized linear models. We found positive relationships with zoochoric plant data and richness of frugivorous mammals. Results that will contribute to the conservation of the domain's biodiversity, considering the effects of climate change and human activities that impact the region in an unsustainable way.