The Diverse Impacts of Grazing, Fire and Weeds: How Ecological Theory Can Inform Conservation Management

Disturbances, such as fire, livestock grazing and introduced weeds, all have profound effects on vegetation structure and the composition of remnant vegetation.Native fauna within remnants frequently shows contrasting responses to vegetation changes; some species increase and others decline. Changes in vegetation structure can alter animal abundance through loss of shelter or foraging areas. However, changes in plant species composition are also influential, because specialist animal species are dependent on particular plants. Predicting the extent of specialization would enable better management by highlighting the components of the vegetation that could be retained or recovered to benefit the most species. Disturbance mosaics seem a logical solution to the diverse response of species to disturbance. However, evidence that tests the intermediate disturbance hypothesis, a model that incorporates the mosaics concept, suggests that mosaics rarely sustain the highest number of species. Given these lessons for management from ecological theory, there is an ongoing need to integrate theory and management. Furthermore, the lack of congruence between the expected benefits of mosaics and the results of intermediate disturbance experiments emphasizes the need for further landscape-scale experiments. Implementing management in the form of designed experiments will be an important part of the solution.