As parks strive to maintain and, in many cases, restore natural processes and ecosystems inside their boundaries, accomplishment of these mandated goals can be confounded by outside activities and actions. Parks do not exist in vacuums, but are connected to the larger landscape that surrounds them. All parks today face threats from invasions of nonnative species, pollution from near and far, and incompatible uses of resources in and around parks. In spite of its geographic isolation, Mesa Verde also contends with environmental issues.
Although most of the land within the park boundaries was not settled in historic times, it has not escaped the sometimes adverse influences of human activity. These activities include the introduction of exotic or invasive plant species; declining air quality due to emissions from nearby coal-burning power plants and visitor and staff vehicles; deteriorating water quality and quantity in the Mancos River due to upstream agricultural uses; physical wear-and-tear as a result of heavy visitation; and grazing and trampling by trespass horses that stray into the park from the adjoining Ute Mountain Ute Indian Reservation.
Mesa Verde also has environmental issues of natural origin that must also be monitored and managed. For example, large-scale wildfires have destroyed over 36,000 acres of old-growth forests and shrublands in the park since 1989. Although there are signs of regrowth, and some areas have been reseeded with native grasses, the natural plant succession in the burned pinyon-juniper forest is being disrupted by an invasion of aggressive, nonnative plant species such as musk thistle and cheatgrass. The dominance of these “invasive weeds” could potentially prevent the natural regeneration of a fully mature pinyon-juniper forest. Each year, the seasonal vegetation crew works hard to reduce the negative effects of the nonnatives. Their goal is to minimize the spread, or where possible, eradicate them through a variety of methods such as applying herbicides, releasing insects that feed on the weeds, reseeding with native plants, or manual/mechanical removal.