Shrub Encroachment Is Linked to Extirpation of an Apex Predator
Journal of Animal Ecology 2017 doi: 10.1111/1365-2656.12607 Shrub encroachment is linked to extirpation of an apex predator Christopher E. Gordon*,1,2,3, David J. Eldridge4, William J. Ripple5, Mathew S. Crowther6, Ben D. Moore1 and Mike Letnic2,4 1Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW 2751, Australia; 2Centre for Ecosystem Science, University of New South Wales, Sydney, NSW 2052, Australia; 3Centre for Environmental Risk Management of Bushfires, University of Wollongong, Wollongong, NSW 2522, Australia; 4School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW 2052, Australia; 5Global Trophic Cascades Program, Forest Ecosystems and Society, Oregon State University, Corvallis, OR 97331, USA; and 6School of Life and Environmental Sciences, University of Sydney, Sydney, NSW 2006, Australia Abstract 1. The abundance of shrubs has increased throughout Earth’s arid lands. This ‘shrub encroachment’ has been linked to livestock grazing, fire-suppression and elevated atmospheric CO2 concentrations facilitating shrub recruitment. Apex predators initiate trophic cascades which can influence the abundance of many species across multiple trophic levels within ecosystems. Extirpation of apex predators is linked inextricably to pastoralism, but has not been considered as a factor contributing to shrub encroachment. 2. Here, we ask if trophic cascades triggered by the extirpation of Australia’s largest terres- trial predator, the dingo (Canis dingo), could be a driver of shrub encroachment in the Strz- elecki Desert, Australia. 3. We use aerial photographs spanning a 51-year period to compare shrub cover between areas where dingoes are historically rare and common. We then quantify contemporary pat- terns of shrub, shrub seedling and mammal abundances, and use structural equation modelling to compare competing trophic cascade hypotheses to explain how dingoes could influence shrub recruitment.
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