B y G r e g o r y M c N a m e e
ENVIRONMENTALISTS WORKING TO protect southern Arizona's San Pedro River from development have long been used to talking in the macrolingo of Big Ideas--biodiversity, sustainability, eco-tourism, environmental ethics. They're experts, too, in invoking the Big Picture, as when, this April, the national eco-lobbying group American Rivers placed the San Pedro and Gila high on its list of America's most endangered and threatened rivers.
Those environmentalists are taking a smaller view these days. The San Pedro's champions, spearheaded by the Arizona chapter of the Nature Conservancy, have a new poster child in a seemingly unlikely candidate, little in size but not in the scheme of things: the Ramsey Canyon leopard frog (Rana subaquavocalis), an 8-inch-long amphibian that turns out to be one of the rarest animals in North America.
Its rarity comes from a curious habit: the Ramsey Canyon leopard frog calls only underwater, and then with an unusually wide repertoire of signals, including a group serenade by which the males attract the females. Biologists have yet to figure out the meaning behind the frog's secretive behavior, but several local researchers are working on the matter.
They may not have much time to figure out why the frogs do what they do. The Ramsey Canyon leopard frog is rare for another reason: There aren't many of them left. Since the discovery of the species just five years ago (Rana subaquavocalis was not officially described until 1993), scientists working with the Nature Conservancy have noted a rapid decline in the frog's population: from about 100 individuals in 1990 to fewer than 25 today.
The frog's decline coincides with that of the San Pedro watershed, generally. Already heavily taxed by irrigated agriculture and ranching, the San Pedro River faces new threats from urban growth, which is draining the little water that remains. Dr. Robin Silver of the Phoenix-based Southwest Center for Biological Diversity puts the matter baldly. "The river's going dry, there's no doubt," he says. "Without emergent action, it's just a matter of when."
Barely 140 miles long from its headwaters in the Sierra Mariquita of northern Mexico to its confluence with the Gila River southeast of metropolitan Phoenix, the San Pedro hosts the largest remaining area of the rarest type of forest ecosystem in the entire United States, what biologists call the "cottonwood-willow riparian association." More than 400 bird species, 82 mammal species, 16 fish species, and 43 reptile and amphibian species, including Rana subaquavocalis, make their home along the river.
The rapid growth of the "Fort Huachuca/Sierra Vista complex," in the parlance of regional planners, puts the river and its nonhuman residents in increasing peril. Those planners have foreseen the growth for years: a University of Arizona study from 1981 warned that increased population would effectively kill the river by the year 2020. Sierra Vista's municipal water needs, combined with ranching and agriculture, already use about 22,000 acre-feet (8 billion gallons) of the San Pedro's water a year--nearly the whole of the river's flow.
In 1993, the Department of Defense recommended that Fort Huachuca, now housing a population of about 22,000 soldiers, be expanded to take on 5,000 troops transferred from other posts. That has since been scaled back to some 250 soldiers to be relocated from Fort Ritchey, Maryland, a small figure by most lights, but still more people in an already overpopulated area.
To halt the growth of the fort, the Huachuca Audubon Society has brought a series of legal actions against the federal government. One, filed a few weeks ago, demands that all federal agencies--among them the departments of Transportation and Housing and Urban Development and the Veteran's Administration--that have any bearing on the fort's future growth not use San Pedro water without consulting with the United States Fish and Wildlife Service and complying with endangered-species regulations.
But that's all Big Picture stuff. Amid this legal and bureaucratic ado, Rana subaquavocalis awaits its day of reckoning.
For their part, conservation scientists are trying to improve the odds for the Ramsey Canyon leopard frog. One program now in the works involves reintroducing the once-common beaver to the San Pedro, behind whose dams the frog population once flourished, thanks to the algae-rich ponds those dams formed. Another indirectly related program, one that local biologists don't much like to talk about, involves killing off the huge population of bullfrogs that have been introduced to southern Arizona from Texas and points east over the last century. The bullfrogs have a habit, it seems, of eating whatever local fauna they can, Rana subaquavocalis included, and they've become a pest.
The Nature Conservancy has also assembled a "conservation rescue squad" made up of scientists and natural-resource managers from the Arizona Game and Fish Department, Forest Service, Bureau of Land Management, Department of Defense and other agencies to establish a program of habitat restoration and captive breeding. The immediate aim is to save Rana subaquavocalis from extinction, and here the federal government proper may not be of much help: The frog is too recently discovered to fall under federal endangered-species protection, whose waiting list is running years behind schedule.
Should it make that sad roster, the Ramsey Canyon leopard frog may make things a lot harder for those who are hoping to build another Tucson-sized metropolis in Cochise County. Just whose side time is on remains to be seen.
Cutline: Rana subaquavocalis: The savior of the San Pedro? Photo by Cecil Schwalbe.
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