An overview of the impacts of feral cattle, water buffalo and pigs on the savannas, wetlands and biota of northern Australia

Abstract

AbstractSince the extinction of the megafauna some 45 000 to 50 000 years ago, grazing pressure on Australian savannas has been relatively low compared to that on savannas in other continents. However, the introduction of several species of ungulate, primarily during the 1800s, and the establishment of large feral populations in northern Australia has resulted in an increase in grazing pressure compared to pre‐colonial times when soft‐footed macropods were the largest extant grazers. Here, we provide an overview of the introduction of three key ungulates to northern Australia: cattle (Bos taurus, B. indicus), Asian water buffalo (Bubalus bubalis) and pigs (Sus scrofa), and the impact of these populations on both abiotic and biotic elements of savanna habitats in northern Australia. Feral ungulate populations have considerable impacts on soil, water quality, waterhole hydrology, vegetation, fire regimes and the spread of exotic plants, and resulting changes to habitat have flow‐on effects for native wildlife. Ungulate impacts on vegetation communities and associated changes in fire regimes are particularly concerning given that sustained grazing can lead to the permanent removal of key grass species and changes in fire intensity and frequency can result in the conversion of grassland to woodland. Native wildlife can be affected by ungulate disturbance in a multitude of ways, but overwhelmingly, habitat loss or degradation is the main driver for declines in biodiversity. Based on current knowledge gaps, we discuss potential directions for future research about how feral ungulate activity affects Australian native species and their impact on savanna habitats.