Chronic anthropogenic disturbance drives the biological impoverishment of the Brazilian Caatinga vegetation

1. In addition to acute transformations of ecosystems caused by deforestation, old-growth forests worldwide are being increasingly altered by low-intensity but chronic human disturbance. Overgrazing and the continuous extraction of forest products are important drivers of chronic disturbance, which can lead to the gradual local extinction of species and the alteration of vegetation structure.
2. We tested this hypothesis in the Brazilian Caatinga vegetation, one of the most species-rich and populated semi-arid regions of the world. Using a multi-model averaging approach we examined the impact of five recognized indicators of chronic disturbance (i.e. proximity to urban centre, houses, roads, density of people and livestock) on the diversity, abundance and evenness of 30 woody plant communities. We separately tested the response of seedlings, saplings, and adults to identify the ontogenetic stages that are most susceptible to chronic disturbance.
3. We recorded over 11 000 individuals ...