Although their impact on the environment is not as severe as some other pests introduced in Australia, camels ingest more than 80% of the plant species available. Degradation of the environment occurs when densities exceed two animals per square kilometre, which is presently the case throughout much of their range in the Northern Territory where they are confined to two main regions: the Simpson Desert and the western desert area of the Central Ranges, Great Sandy Desert and Tanami Desert. Some traditional food plants harvested by Aboriginal people in these areas are seriously affected by camel-browsing. While having soft-padded feet makes soil erosion less likely, they do destabilise dune crests, which can contribute to erosion. Feral camels do have a noticeable impact on salt lake ecosystems, and have been found to foul waterholes.