Tamarisk control, water salvage, and wildlife habitat restoration along rivers in the western United States

In the latter part of the 19th century, species of the nonnative shrub tamarisk (also called saltcedar; for example, Tamarix ramosissima, T. chinensis) were introduced to the United States for use as ornamental plants for erosion control. By 1877, some naturalized populations had become established, and by the 1960s, tamarisk was present along most rivers in the semi-arid and arid parts of the West and was quite abundant along downstream ranches of the major southwest rivers such as the Colorado, Rio Grande, Gila, and Pecos. The principal period of tamarisk invasion coincided with changing physical conditions along western rivers associated with the construction and operation of dams. In many cases, these altered physical conditions appear to have been more favorable for tamarisk than native riparian competitors like cottonwoods and willows (Populus and Salix; Glenn and Nagler, 2005).

The great abundance of tamarisk along western rivers has led resource managers to seek to control it for various reasons, including a desire to (1) increase the flow of water in streams that might otherwise be lost to evapotranspiration (ET) (evapotranspiration is the combination of water lost as vapor from a soil or open water surface [evaporation] and water lost from the surface of the plant, usually from the stomata [transpiration]); (2) restore native riparian vegetation (here, “riparian” refers to the banks and flood plains of rivers, or shorelines of reservoirs or lakes); and (3) improve wildlife habitat.