Use by visitors is both a primary reason for the establishment of national parks and a factor in the condition of many of the natural and cultural resources that the parks are intended to protect. While poaching and road collisions have immediate consequences for wildlife, most visitor impacts are less obvious. The long-term consequences of some previous park policies carried out for the presumed benefit of visitors—such as predator control and the introduction of non-native fish—continue to be evident in the parks today. In addition, ongoing visitor activities and associated infrastructure affect many park resources, including:
- air and water quality, and the natural soundscape;
- wildlife habitat, distribution and habituation;
- the spread of non-native plants, diseases, and aquatic organisms;
- the functioning of geothermal features; and
- the preservation of archeological sites and other cultural artifacts.