Battling Invasive Species in Arches National Park

This grove of tamarisk was spotted along the Little Colorado River in Arizona. Photo by John Grahame.

Our national parks are places of incredible beauty and rich history. There are fewer finer days than those spent in a national park. And yet, for all their beauty, these places also are under siege by non-native species. An understanding of these threats is essential if we are to protect the National Park System for future generations.

Across the system, the landscape is being invaded by "exotic" species that are not just out of place, when you consider what should be growing, swimming or crawling, but in some cases are actually driving out the natives.

In the Southwest, parks such as Arches, Canyonlands, Zion, and the Grand Canyon a non-native species known as "tamarisk" and at times as "salt cedar" is literally invading the landscape.

Showy when in bloom with its feathery branches and pink flowers, the shrubby tree was brought into the United States in the 1850s from its native North Africa, the Mediterranean, and the Middle East. Once established, this thirsty species not only is adept at monopolizing available water but also stockpiles salt within its leaves, a process that can boost the normal alkalinity of the surrounding soil and poison native plants when the leaves fall off.

Tamarisk is also particularly tough to eradicate. In the accompanying video, produced as part of Montana State University's M.F.A. in Science and Natural History Filmmaking program thanks to a National Park Service grant, rangers at Arches National Park describe the problems posed by tamarisk.

You can learn about other vegetative invaders at this site.


You're right Kurt, invasive species are a huge problem facing our national parks. A system-wide review ( of the condition of America’s national parks by the National Parks Conservation Association found that invasive species are a limited concern in 90 percent of the parks evaluated, and are considered a widespread or chronic concern in 38 percent. Eighty-two percent of assessed parks have experienced the extirpation of one or more species, while 40 percent of sampled parks have lost a key species or top predator.

NPCA also just recently released an assessment of Hawaii Volcanoes National Park ( and ranked natural resources of the park in "poor" condition, scoring an overall 60 out of 100 points, primarily because the park battles non-native plants and animals that threaten to overtake native species, many of which are found nowhere else in the world.

Hawaii Volcanoes has among the highest number (54) of threatened and endangered plants and animals in the National Park System, largely due to non-native species, which the National Park Service is working aggressively to eradicate. But because of a lack of funding, the park can only actively monitor and protect four (out of 54) species that it identifies as flagship species: the hawksbill turtle, Hawaiian petrel, Hawaiian goose, and Mauna Loa silversword plant.