One of the larger issues the region faces are populations of invasive species. Invasive species have the biggest impact on the region. Population increases of red deer, and other browsing mammals such as wapiti, goat, and fallow deer, have caused severe damage and particularly threaten the integrity of the forest and alpine ecosystems. Commercial hunting has been used as a means of reducing these populations to ecologically acceptable levels. The Department of Conservation has control programs and the National Parks policy is to eradicate new invasions and eradicate or reduce the range of existing invasive species