Abstract
For prioritizing conservation actions, it is vital to understand how ecologically diverse species respond to environmental change caused by human activity. This is particularly necessary considering that chronic human disturbance is a threat to biodiversity worldwide. Depending on how species tolerate and adapt to such disturbance, ecological integrity and ecosystem services will be more or less affected. Bats are a species-rich and functionally diverse group, with important roles in ecosystems, and are therefore recognized as a good model group for assessing the impact of environmental change. Their populations have decreased in several regions, especially in the tropics, and are threatened by increasing human disturbance. Using passive acoustic monitoring, we assessed how the species-rich aerial insectivorous bats—essential for insect suppression services—respond to chronic human disturbance in the Caatinga dry forests of Brazil, an area potentially harboring ca. 100 bat species (nearly 50% are insectivorous), but with > 60% its area composed of anthropogenic ecosystems under chronic pressure. Acoustic data for bat activity was collected at research sites with varying amounts of chronic human disturbance (e.g., livestock grazing and firewood gathering). The intensity of the disturbance is indicated by the global multi-metric CAD index (GMDI). Using Animal Sound Identifier (ASI) software, we identified 18 different bat taxon units. Using Hierarchical Modeling of Species Communities (HMSC), we found trends in the association of the disturbance gradient with species richness and bat activity: species richness was higher at sites with higher human disturbance, whereas bat activity decreased with increasing human disturbance. Additionally, we observed taxon-specific responses to human disturbance. We conclude that the effects of chronic anthropogenic disturbance on the insectivorous bat fauna in the Caatinga are not homogeneous and a species-specific approach is necessary when assessing the responses of local bats to human disturbances in tropical dry forests, and in other biomes under human pressure.
Highlights
Human activity is responsible for the most significant threats to biodiversity, including habitat degradation and excessive use of natural resources [World Wide Fund for Nature [WWF], 2018]
Given the widespread threat to the conservation of the Brazilian Caatinga represented by intensive cultivation and grazing from livestock, the assessment of the effects of anthropogenic changes on the structure of bat assemblages may produce practical results useful for conservation and restoration
We investigated the relationship between human disturbance, bat activity and species richness of insectivorous bats considering responses of different taxa at sites under different anthropogenic degrees in Brazil’s Caatinga drylands
Summary
Human activity is responsible for the most significant threats to biodiversity, including habitat degradation and excessive use of natural resources [World Wide Fund for Nature [WWF], 2018]. To facilitate conservation of global biodiversity, it is vital to understand how ecologically diverse species cope with environmental change caused by anthropogenic disturbance. Some taxa are able to adapt to modified environments where they can utilize human-based resources, such as artificial food or man-made structures (Prange et al, 2004; Ávila-Flores and Fenton, 2005). Other species are not found in disturbed areas as they depend on food, shelter and habitats that only natural sites can sufficiently offer (Mckinney, 2009). Information on the ecological needs of individual species is required to predict the risks of local extinction and to propose adequate conservation strategies in an increasingly impacted world
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