For Immediate Release, October 6, 2021


Robin Silver, Center for Biological Diversity, (602) 799-3275,
Mark Larson, Maricopa Audubon Society, (480) 310-3261,

Lawsuit Targets Trespass Grazing Destruction of Endangered Plant in Arizona’s San Pedro Riparian National Conservation Area

TUCSON, Ariz.— The Center for Biological Diversity and Maricopa Audubon Society sued the U.S. Bureau of Land Management today for failing to protect a semi-aquatic endangered plant in the San Pedro Riparian National Conservation Area from rampant trespass livestock grazing.

Today’s lawsuit, filed in U.S. District Court in Tucson, says the Bureau of Land Management has violated the Endangered Species Act by ignoring needed fence repairs and trespassing cattle that put the Huachuca water umbel and its wetlands habitat at risk.

“Nearly all the core population of these highly endangered, delicate plants have been annihilated. They don’t stand a chance against the cows,” said Robin Silver, a cofounder of the Center. “We’ve been fighting for decades to save the San Pedro and its plants and animals. The BLM is either too timid or too apathetic to protect this fragile ecosystem from neighboring ranchers, whose cows are ravaging the river and pushing the water umbel closer to extinction.”

The Huachuca water umbel is an herbaceous, perennial plant with slender, erect leaves. The plants once flourished in extensive riparian habitats in southeastern Arizona and northern Sonora, Mexico, but have been reduced to several disconnected clumps in a handful of Southwest wetlands. In 1996 the Center petitioned the U.S. Fish and Wildlife Service to protect the plant under the Endangered Species Act, and it was listed the following year.

The San Pedro Riparian National Conservation Area was the nation’s first, created by Congress in 1988. It includes more than 46 miles of the San Pedro and Babocomari rivers and nearly 55,000 acres of riparian areas and uplands, including four of the rarest habitat types in the Southwest: cottonwood/willow forests, marshlands, grasslands and mesquite bosques.

More than 400 birds, 50 species of reptiles and amphibians, and 80 species of mammals are found in the conservation area, making it a world-renowned biodiversity hotspot.

“For years the BLM has turned a blind eye as cattle defecate and trample these beautiful wetlands and the water umbel to death,” said Mark Larson, president of the Maricopa Audubon Society. “The plant’s health is an indication of how the whole ecosystem is doing, and sadly the San Pedro Riparian National Conservation Area is on life support with its BLM caretakers out to lunch.”

In addition to trespass cattle in the conservation area’s wetlands, the threats to the Huachuca water umbel include drought, climate change and declining groundwater levels from development and over-pumping.

Other endangered species in the area include Southwestern willow flycatchers, ocelots, jaguars, desert pupfish, Gila topminnows, western yellow-billed cuckoos, northern Mexican garter snakes and Arizona eryngo.

In a May 2018 letter to the BLM, 21 scientists urged the agency to exclude livestock grazing from the conservation area. Allowing livestock grazing here jeopardizes its many aquatic and riparian species and the area’s critically important role as an ecological reference site, they wrote.

The area is the traditional territory of the Chiricahua Apache, Opata, O’odham, Hohokam and Sobaipuri people.

San Pedro Riparian National Conservation Area. Photo credit: Robin Silver Image is available for media use.

The Center for Biological Diversity is a national, nonprofit conservation organization with more than 1.7 million members and online activists dedicated to the protection of endangered species and wild places.