Tamarisk ( Tamarix spp .), commonly known as salt cedar, is an exotic (non-native) shrub or tree that grows in dense stands along rivers and streams in the west. Tamarisk, introduced to the U.S. in the 19th century as an erosion control agent, spread through the west and caused major changes to natural environments. Tamarisk reached the Grand Canyon area during the late 1920s and early 1930s, becoming a dominant riparian zone species along the Colorado River in 1963 (following completion of Glen Canyon Dam).

The impacts caused by tamarisk in the southwest are well documented. These prolific non-native shrubs displace native vegetation and animals, alter soil salinity, and increase fire frequency. Salt cedar is an aggressive competitor, often developing monoculture stands and lowering water tables, which can negatively affect wildlife and native vegetative communities. In many areas, it occupies previously open spaces and is adapted to a wide range of environmental conditions. Once established in an area, it typically spreads and persists.