• Double O Arch

    Arches

    National Park Utah

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    Due to extremely dry conditions, fire restrictions are in effect in all national park units in Southeast Utah. More »

Tamarisk

Extensive Tamarisk removal has helped native cottonwoods in Courthouse Wash
Extensive Tamarisk removal has helped native cottonwoods in Courthouse Wash
NPS Photo by Tom Gray
 
Of the non-native plant species in Arches, tamarisk is often seen as the most troublesome. This water-loving, Mediterranean plant arrived in North America in the 1800's. It was used initially as an ornamental shrub, and was later planted by the Department of Agriculture to slow erosion along the banks of the Colorado River in Arizona. Spreading upriver at roughly 12 miles per year, tamarisk is now established on all of the Colorado’s tributaries.

Once established, dense tamarisk stands increase fire frequency, lower plant and animal diversity, and significantly alter stream hydrology. Tamarisk consumes a great deal of water, and rarely provides food and shelter necessary for the survival of wildlife. Mature cottonwood communities are declining because shading inhibits the growth of their seedlings.

Courthouse Wash in Arches is one of several sites where the National Park Service has made an effort to control tamarisk. Similar control experiments have been established in nearby areas, mostly in small, tributary canyons of the Colorado River.

Did You Know?

Close up of biological soil crust

The dirt is alive! A living crust called "Biological Soil Crust" covers much of Arches and the surrounding area. Composed of algae, lichens and bacteria, this crust provides a secure foundation for desert plants. Please stay on roads and trails to avoid trampling this important resource. More...