Invasive Species
The National Park Service defines exotic species as those occurring in a given place as a result of actions of humans. Compared to parks in the rest of the United States, the National Park Service units in Alaska are relatively pristine in terms of exotic plants. One herb, Melilotus alba (white sweet clover), has invaded naturally open areas in Denali, Alaska. Another herb, Vicia cracca (bird vetch), not only invades stands of native shrubs and tree saplings, but also climbs and spreads over native plants. This plant spreads slowly and is not yet a problem in Denali or other parks in Alaska, but is a threat to many parks nationwide.
Several factors have protected Alaskan parks from exotic plants. The first protecting factor is climate because many plants that could cause a threat to native plants in Denali are not adapted to the extreme temperatures/diverse terrains in the park. In particular, low soil temperatures and/or permafrost.
The second protecting factor is that park ecosystem components and processes are relatively undisturbed in Alaska. Alaskan parks have all the pieces, including key predators, herbivores, and a relatively natural wildfire regime. Ecosystems in parks in other states, by comparison, have been altered by livestock grazing, wildfire suppression, and other factors that ease the entry of exotic species.
The third protective factor is that most parks in Alaska are large enough to include all the ecosystem pieces, and are surrounded by undeveloped lands. In comparison, most parks in other states are islands in a sea of altered ecosystems with many invasive exotic plants.
In spite of these protective factors, the threat to parks in Alaska from exotic plants is increasing and Denali is no exception. New exotic plants are appearing, and some of those already present are spreading rapidly. Environmentalists in the park are working hard to control/stop th4e spread of these invasive species.
Several factors have protected Alaskan parks from exotic plants. The first protecting factor is climate because many plants that could cause a threat to native plants in Denali are not adapted to the extreme temperatures/diverse terrains in the park. In particular, low soil temperatures and/or permafrost.
The second protecting factor is that park ecosystem components and processes are relatively undisturbed in Alaska. Alaskan parks have all the pieces, including key predators, herbivores, and a relatively natural wildfire regime. Ecosystems in parks in other states, by comparison, have been altered by livestock grazing, wildfire suppression, and other factors that ease the entry of exotic species.
The third protective factor is that most parks in Alaska are large enough to include all the ecosystem pieces, and are surrounded by undeveloped lands. In comparison, most parks in other states are islands in a sea of altered ecosystems with many invasive exotic plants.
In spite of these protective factors, the threat to parks in Alaska from exotic plants is increasing and Denali is no exception. New exotic plants are appearing, and some of those already present are spreading rapidly. Environmentalists in the park are working hard to control/stop th4e spread of these invasive species.