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River Partners Expands to Southern CA & Arizona

Restoration planning underway on the Otay River Watershed and Lower Colorado River

Throughout the Southwest’s desert, chaparral, and coastal sage scrub landscape, narrow riparian corridors spring up along various streams and rivers and support high concentrations of wildlife and plant species.

Recently, though, wildfires have decimated large swaths of riparian areas in San Diego County and the California- Arizona border. In these areas, invasive weeds, like arundo and salt cedar (tamarisk), have supplanted native plant communities. Through two restoration planning studies for the Otay River Watershed and the Lower Colorado River, respectively, River Partners’ hopes to make a big difference for wildlife and the regions’ fire recovery efforts.

Our work in the Otay Valley, San Diego County

San Diego County has the greatest number of threatened and endangered species of any county in the continental U.S, which makes it an ideal place for River Partners’ restoration work. These species need help, and River Partners has the expertise to bring back riparian zones and improve this critical biodiversity hotspot. River Partners has received funding from the Resources Legacy Fund Foundation (RLFF) to develop a pre-restoration plan for the Otay watershed with particular focus on the Otay Valley Regional Park (OVRP).

Like most watersheds in California, the Otay River has been heavily impacted by human use. Increasing wildfire frequency is causing a type change in the rural portion of the watershed – from riparian and coastal sage scrub to streams overrun with noxious weeks, like arundo and tamarisk. Flowing towards San Diego Bay, the Otay River enters into urbanized Chula Vista where all traces of historical hydrology disappear. For River Partners there will be a wide array of potential projects, each with a unique set of biological parameters.

At this time we have conducted a preliminary evaluation of the watershed and have identified potential project sites, targeted for helping threatened and endangered species and other wildlife dependant on this important habitat corridor. The projects will also provide critical habitat and open space improvements to typically underserved communities.

There are several listed species which currently breed or have the potential to breed within the proposed project area. Federally endangered wildlife, such as the least Bell’s vireo, California gnatcatcher, and the arroyo toad occur in this stretch. Another endangered bird – the southwestern willow flycatcher – bred in the OVRP as recently as 1996. Many species of special concern also occur in this area including yellow-breasted chat and yellow warbler.

Species diversity, richness, and abundance are significantly higher in riparian areas than other surrounding habitats such as grassland, coniferous forests or coastal sage scrub. Should riparian areas continue to become marginalized by the invasion of non-native plant species and loss of open space, further local declines in these species can be expected. However, taking steps to bring back riparian habitat, which is River Partners’ goal, will benefit San Diego’s wildlife significantly.

Our work along the Lower Colorado River

The Cibola National Wildlife Refuge near the California-Arizona border. Photo by River Partners staff.

Located on the Lower Colorado River on the Arizona-California border, the Cibola National Wildlife Refuge (CNWR) is a critical area for species like the yellowbilled cuckoo and the southwest willow flycatcher. Unfortunately as a result of wildfire damage, salt cedar (tamarisk, a noxious weed) dominates former riparian zones. This diminishes the value of the refuge for wildlife and further increases wildfire risk.

To assist the CNWR with its wildfire recovery plan, River Partners has begun evaluating the area for potential restoration sites. “We’re developing a pre-restoration plan of up to 1,000 acres,” says Tom Griggs, River Partners Senior Restoration Ecologist. “The goal is to prioritize areas that would have the most success if restored. However, the challenge that Michelle Ohrtman, our project ecologist, faces is understanding the salt concentration of the soils and determining the ground water situation. Our plant design recommendations will depend on knowing these particular conditions.” Considering this region experiences lower precipitation than California’s Central Valley, River Partners’ prerestoration design will rely on fewer woody species. In other words, there will be fewer colors in our palette, but our design still will offer complexity. Some of the species River Partners anticipates using are Freemont cottonwood, mulefat, black willow, and quail bush. For higher areas, the plan could include mesquite and wolf berry.

River Partners’ goal is to build on the Cottonwood restoration efforts initiated within CNWR. As in San Diego, bringing back critical riparian areas will provide a huge benefit to the resident and migrating species. In fact southwest riparian is listed in the American Bird Conservancy’s “Top 20 Most Threatened Bird Habitats in the U.S.”

The above article originally appeared in the Fall 2008 issue of the River Partners Journal.