Impact of Red Kangaroos on the Pasture Layer in the Western Australian Arid Zone.

Abstract

We studied the impact of grazing by red kangaroos (Macropus rufus) on pasture biomass and species diversity over a 32-month period in destocked open shrubland in the Gascoyne region of Western Australia. Grazing significantly impeded the accumulation of annual and perennial grass biomass in a degraded perennial shrub community (Pc0.001 and P<0.05) and on denuded sites that were cultivated and reseeded with native shrubs (P<0.01 and Pc0.01). The accumulation of annual and perennial forb biomass was unaffected by kangaroo grazing. After 12 months, pasture species diversity was significantly greater on degraded perennial sites protected from kangaroo grazing (P<0.05). Commercial kangaroo shooting did not alleviate the impact of kangaroo grazing on grass accumulation (P<0.01). Unless more effective methods of kangaroo control are integrated with stock reductions, the recovery of degraded rangeland pastures is likely to be severely limited.