Tamarisk is strangling riparian ecosystems.
The once-open beaches and cottonwood galleries along the Colorado River and many other western rivers have all but disappeared. Instead, densely crowded stands of tamarisk, interspersed with Russian olive, have replaced sandy beaches and native plants. The takeover has been so complete that wildlife habitat has been degraded, recreational beaches have shrunk, and millions of acre-feet of water have been lost. This invasion of exotic plants, compounded with escalating populations and global warming in the form of drought, are putting huge pressures on western water supplies.
Tamarisk was introduced from Eurasia in the early 1900s for its beauty and ability to control bank erosion. From California, it galloped up the Colorado River basin, crowding out native plants and becoming a monoculture in places. Tamarisk has deep roots, up to 100 feet, and can use large quantities of water. This, coupled with a propensity to create dense stands, and stands in xeric (drier) areas that thrifty native plants usually occupy has given tamarisk a bad reputation for large water consumption, a theory now being questioned by scientists.