Heating a biodiversity hotspot: connectivity is more important than remaining habitat

Abstract

Connectivity, which is a fundamental aspect of any landscape, has been shown to have a nonlinear relationship with the amount of natural habitat, with a marked decrease at intermediate levels of coverage. Impacts on connectivity vary according to how natural habitat is removed. We analyzed connectivity in the Brazilian Cerrado (tropical savanna), a 2 million-km2 biodiversity hotspot. We evaluated the effects of habitat removal on connectivity, hypothesizing that a deforestation threshold exists below which connectivity is drastically reduced and that neighboring landscapes have similar patterns of connectivity. We divided the Cerrado into 624 50 × 50 km cells and used the integral index of connectivity (IIC), available in Conefor software, to evaluate changes in connectivity between 2000 and 2017. We analyzed how the intra, flux, and connector components of connectivity vary with changes in percentage of remaining natural habitat. Between 2000 and 2017, 23.9% of the natural habitat of the Cerrado was lost (~ 254,000 km2) and connectivity decreased significantly (W = 179,700, p < 0.01). The most crucial change was the removal of connector fragments or corridors, which occurred in 78.2% of the landscapes. The relationship between IIC and remaining natural area revealed a breakpoint, when native area in a landscape reached 39% in 2000 and 37% in 2017. Regardless of the spatial arrangement of habitat fragments, landscape connectivity is lost when the remaining natural habitat falls below a certain threshold. More restrictive regulations and government permissions should be considered to avoid over-occupation of landscapes.