Currently, Australia has at least 400,000 horses roaming the continent. It is also estimated that, during non-drought periods, the feral horse population increases at a rate of 20 percent per year. Drought conditions and brushfires are natural threats. Despite population numbers, feral horses are generally considered to be a moderate pest. Where they are allowed to damage vegetation and cause erosion, the impact on the environment is significant, and for that reason can be considered a serious environmental threat. However, because they also have cultural and potential economic value, the management of brumbies presents a complex issue.