Ecosystem

Habitat restoration is one of the main goals of the Army Corps Feasiblity Study for the Los Angeles River.

Bird species of special concern found along the River Corridor include:

  • American White Pelican   
  • Double Crested Cormorant
  • Osprey
  • Northern Harrier
  • Sharp-shinned Hawk
  • Coopers Hawk
  • Merlin
  • California Gull
  • Vaux’s Swift
  • Loggerhead Shrike
  • Yellow Warble
  • Yellow-breasted Chat
  • Tri-colored Blackbird

(California Department of Fish and Game, Habitat Conservation Planning Branch, 2007, website).

More rarely seen species include: Least Bittern, White-faced Ibis, Golden Eagle, Prairie Falcon, Long-billed Curlew, Burrowing Owl, Vermillion Flycatcher, California Horned Lark, and Summer Tanager.

(San Fernando Valley Audubon Society, pers. comm., 2007).

According to the California Coastal Conservancy, close to 100 percent of the original wetlands and 90 to 95 percent of in-stream riparian habitat within the Los Angeles River watershed have been lost, a consequence of urbanization and the channelization of rivers and creeks. Within the 32-mile Los Angeles River project area, the only areas that presently support riparian habitat are Sepulveda Basin and the Glendale Narrows. These areas are increasingly stressed by exotic species, hydrologic modifications, dumping of trash and debris, and encroaching development.

The 225-acre Sepulveda Basin Wildlife Preserve is the only officially designated wildlife area along the River, within the City. The soft-bottom portions of the River here and at the Glendale Narrows provide valuable resting and feeding zones for migratory birds, yet these areas are seasonally inundated with high flows, which often preclude nesting. Key indicator species found within these areas include a variety of mammals and birds, such as coyote, shrike, acorn woodpeckers, and California quail. Urban runoff and sewage treatment plants provide a majority of the water flowing in the channel; and this nutrient rich water supports unique riparian ecologies along the River.

Riparian habitat is also often impaired by degraded water quality (for example, increases in water temperature, the quantities of sediment and nutrients, and pesticides and heavy metals), and elimination or reduction of adjacent "buffer habitat." Because functional riparian habitat and wetlands can improve water quality by removing or sequestering many contaminants, the loss of this habitat has implications for the ecological functioning of the River, as well as for wildlife uses. In addition to the largely disconnected riparian habitat along the River corridor, upland and riparian connections to mountain areas are largely absent, except along Verdugo Wash. Restoring and reconnecting both riparian and upland habitat, and recreating wetland areas where feasible, would contribute a great deal to the restoration of a functional ecosystem along the River. Some potential wildlife connections at critical conservation areas such as from the Arroyo Seco to Elysian Park and Griffith Park to Verdugo Wash would also enhance connectivity.

The steelhead trout is a hardy fish with powerful survival mechanisms; the main barrier to the steelhead trout’s "recolonization" of the River is not temperature or water quality -- though these remain factors -- but an unimpeded path from the ocean to the headwaters, along with areas in which to rest and spawn. Such an unimpeded pathway would require removing enough of the concrete within the channel to allow a fish to journey from the ocean to the headwaters, via a system of pools, riffles, runs, and gravel. Significant riparian cover or other mechanisms would provide shade, and a natural flow regime of high and low-flows would be necessary.

The Los Angeles River watershed includes three regionally significant ecological areas (SEA’s) that are disconnected from the River corridor, these are: the Santa Monica Mountains, Verdugo Mountains, and Griffith Park. As noted in the Los Angeles County’s 1996 Los Angeles River Master Plan, migratory and resident birds move along the major flyways between the River, the SEA’s and other sites with surface water such as Hansen Dam, and the Sepulveda Basin. Open freshwater reservoirs such as the Los Angeles, Pacoima, Encino, and the Tujunga also offer feeding and nesting grounds. According to research by the University of Southern California’s GreenVisions program (2006), the channel and rights-of-way currently function as movement corridors for mammals.