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SAN LUIS NWR: Grazing Plan at San Luis NWR Refuge Benefits Multiple Conservation Partners in Midst of California’s Historic Drought
California-Nevada Offices , April 14, 2014
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Cattle grazing to control weeds in upland areas adjacent to the San Joaquin River on the San Luis NWR.
Cattle grazing to control weeds in upland areas adjacent to the San Joaquin River on the San Luis NWR. - Photo Credit: USFWS
Long-billed Curlews are one of many native wildlife species found on the San Luis NWR that thrive in lush short-grass habitats resulting from cattle grazing.
Long-billed Curlews are one of many native wildlife species found on the San Luis NWR that thrive in lush short-grass habitats resulting from cattle grazing. - Photo Credit: USFWS

By Madeline Yancey

The conservation work of the U.S. Fish and Wildlife Service is critically dependent on partnerships. The ongoing historic drought in California has presented the opportunity for multiple partners of the San Luis NWR Complex in Los Baños to work together for their mutual benefit and the benefit of wildlife and the habitat on which it depends.

River Partners is a non-profit conservation organization that has been a valued long-time partner to the San Luis NWR Complex. River Partners specializes in riparian habitat restoration and performed one of the largest riparian woodland restorations in California on more than 2,700 acres of the San Joaquin River NWR. One of their current projects is the control of exotic invasive weeds for the San Joaquin River Restoration Program along the riparian corridor that includes a nine-mile section of the river that flows through the San Luis NWR.

Some 300 acres between the riparian woodland and the flood-control levee are heavily infested with noxious invasive weeds like perennial pepperweed, poison hemlock and yellow star thistle. Some patches of perennial pepperweed are as large as 30 acres. Several options are available for dealing with the undesired weed species, but all come with limitations. Burning the targeted weeds would damage the important native riparian trees – oaks, cottonwoods and willows. The drought has made conditions far too dry to use mechanical equipment to mow the weeds for fear of sparks igniting dead dry vegetation and the terrain is not safe for mechanical equipment. Therefore, herbicide application is the method of choice, but the areas requiring treatment are extremely dense with tall dead weeds. Those conditions make it impossible for River Partners to get into the sites with their spray equipment. Even if they could, little of the herbicide would actually make contact with the target species. The dead vegetation must be flattened or removed to facilitate site access and efficient application of the herbicide.

Another long-time partner is a local rancher who has benefitted from grazing opportunities for his cattle on the San Luis NWR, so too have habitats on the refuge benefitted from the grazing “services” provided by those cattle. The Arena Plains and Snobird units support remnants of the unique and endangered vernal pool and sand dune plant communities' native to the San Joaquin Valley floor. Each year at the opportune time, cattle are allowed onto the units to graze the exotic grassland plant species – setting the stage for the fleeting appearance and brief life cycle of native wildflower species like goldfields, birds-eye gilia and purple owl’s clover; species that cannot survive growing amongst the taller exotic grass community. Other low-growing grassland species benefit from cattle grazing, such as the state-listed endangered Delton Button Celery.

This year 300 head of cattle, 150 cows and 150 yearlings, are waiting in the wings to begin grazing the grasslands of Arena Plains and Snobird, but there is no forage for them to graze thanks to the drought and the driest calendar year on record (2013). The refuge has many sites on which management practices have included cattle grazing, but the drought has reduced forage available there as well. The rancher brought his cattle in from rangeland in Wyoming to provide a service, but is now having to feed them hay at a cost of nearly $700 per day.

The rancher, refuge staff and River Partners came together and devised a plan that would benefit all parties and ultimately, the restoration of wildlife habitat along the San Joaquin River. Those 300 head of cattle will be selectively permitted to graze the weed-infested areas along the riparian corridor. Grazing cattle can make short work of knocking down the dense dead vegetation that would keep the herbicide applications from hitting their mark, but if not carefully managed, they could damage the habitat in the riparian woodland. The cattle’s high-nitrogen waste concentrated under the riparian trees could kill them. The herd’s trampling of the moist soft soils along the riverbank would compact soil around tree roots and cause erosion into the river. Increased nitrification could result from the leaching of concentrated animal waste into the water.

Therefore, the grazing cattle will be restricted to the upland areas between the trees and the levee by 75- to 100-acre enclosures surrounded with electrified “hot” wire. The enclosures will be set up in areas dominated by the exotic weeds, avoiding homogeneous stands of riparian natives like mugwort, sandbar willow and red willow. The cattle will be moved around over the course for approximately 60 days; so as to have high impact on the weedy areas and no impact to stands of native plant species. The entire operation will be “short and sweet” because the riparian corridor will soon be a flurry of reproductive activity as the heron and egret rookeries and nesting songbirds get busy with the work of mating, nest building, egg laying and raising young.

Ultimately, the riparian corridor will be reseeded with native grass and forb species as part of habitat restoration designed to re-establish the dynamic links between the living river and the adjacent riparian woodland. A thriving riparian plant community will provide shade to the river, helping to maintain the temperature range required by the (soon to be re-introduced) native Chinook salmon for spawning and for their eggs and fry. The plants will also support robust insect populations to feed the fish, other aquatic vertebrates and riparian songbirds. Once again, partners in conservation and their thriving relationships will help make it happen.

Madeline Yancey is a Park Ranger (Visitor Services) at the San Luis NWR Complex in California.


Contact Info: Jack Sparks, 209-826-3508, jack_sparks@fws.gov



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