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At high densities kangaroo grazing can reduce biodiversity

Hot Topics in Ecology

At high densities kangaroo grazing can reduce biodiversity

Brett W A Howland, Australian National University, Pr. Don A. Driscoll, Deakin University
Overabundant kangaroos graze away the habitat that other native species depend on for survival. Photo by Graeme Coulson

Over-grazing by herbivores can simplify the structure, composition and function of vegetation communities by reducing vegetation cover and diversity, increasing soil degradation and driving biodiversity loss. European colonisation has created ideal conditions for the eastern grey kangaroo in south-eastern Australia, thanks to dingo eradication, new permanent watering points, protection from hunting and increased pasture availability. Consequently, in some areas, kangaroo population densities have risen to levels where impacts on other native species are occurring. At high densities, kangaroo grazing can: (1) reduce the occurrence, height and seeding rates of some native grasses; (2) reduce the diversity and cover of native shrubs following fire; (3) reduce the abundance and diversity of beetles; (4) reduce the overall abundance and diversity of reptiles; (5) reduce the quality of habitat for some species of legless lizards and the three-toe earless skink; (6) reduce the occurrence of the vulnerable striped legless lizard; (7) reduce the quality of habitat for many species of bird; and (8) reduce the quality of habitat for endangered eastern barred bandicoots, threatening a reintroduction program. In particular, the striped legless lizard appears very sensitive to high grazing. One recent study suggested that detection of this species more than halved with each doubling of kangaroo density. The impacts of high density kangaroo grazing on biodiversity in Australia are consistent with studies on native herbivores overseas, where predation and hunting that regulated herbivore density have diminished. Managing grazing pressure is often required to prevent biodiversity loss and ecosystem degradation.

Hot Topic Lead Author: 
Name: Brett Howland
Email: brett.howland@anu.edu.au
Phone: 03 92517609

Name: Professor Don Driscoll
Email: d.driscoll@deakin.edu.au
Phone: 03 92517609