And it all began so innocently.
"The invasion of exotic grasses to the Sonoran Desert is an ecological dilemma of significant magnitude," says Gary Paul Nabhan, former Arizona-Sonora Desert Museum conservation director. "Whether we walk around in the heart of our city or retreat to the most remote wilderness stretches along the U.S.-Mexico borderlands, it's likely at least one of 600 non-native plant and animal species can be found welcoming us to the Planet of the Weeds."
Of greatest concern to those who study such matters is buffelgrass, a drought-tolerant perennial herb native to Asia and South Africa. Introduced by Department of Agriculture and U.S. Soil Conservation Service scientists in 1939 with promising expectations of providing low-elevation forage, it has become a scourge that ranges from central Arizona to Hermosillo, Sonora, and covers millions of acres in the southwest and Mexico. In many places, it has permanently crowded out and replaced native vegetation. And concern involves economic as well as environmental impact. Buffelgrass and other non-native plants and animals cost taxpayers an estimated $123 billion per year in damages, losses, monitoring and control, according to Department of the Interior and National Parks folks at Saguaro National Park.
Plant experts had hoped this rapidly-growing, drought-tolerant, large perennial bunchgrass would provide graze for livestock as well as slow down soil erosion caused by overgrazing of cattle. Instead, what it did was escape its experimental plots, aggressively colonize and spread exponentially. Buffelgrass robs the soil of nitrogen and phosphorous and competes with native plant species for nutrients, space and water, but its most serious danger involves fire. Desert fires used to be rare because plants were generally too far apart for the flames to spread. Since the arrival of non-native grasses, desert burns have increased in both frequency and magnitude.
"These grasses have evolved and adapted to fire. It may take a long time, but they'll spring back from a burnout, wipe out the competition and take over a desert, turning it into a treeless plain full of drought-resistant undergrowth," says former Desert Museum curator of botany Barbara Skye Siegel.
To prevent such a catastrophe from happening, a group of volunteers known as the Sonoran Desert Weedwackers, founded by Siegel, have come to the rescue.
"We were aware it was a growing problem, one of those silent things that creeps up on you little by little until it explodes into a big problem due to the sheer biomass of the plant," she says. Indeed. invasive plants now infest more than 100 million acres in the United States, and 3 million of these acres are lost each year due to the invasion. Directors at the Sonoran Institute, The Nature Conservancy and Arizona-Sonora Desert Museum are unanimous in their concern that the problem is, in their terms, "a subtle, late-breaking, and quietly astonishing ecological crisis."
Under the "think globally, act locally" concept, volunteer weed-wackers (backed up by their more-experienced SWAT group--Southwest Weed Attack Team) gather on fall weekends for hands-on, labor-intensive environmental therapy. "We've cleared something close to 5,000 acres so far," says Doug Siegel, Pima County Parks representative for Tucson Mountain Park. "If you really love where you live--the attractions of the Sonoran Desert that brought most of us here in the first place--you have to care about the negative potential of these invasive species."
Like volunteer John Gorto, a recent arrival from Michigan, who participated in an October clean-up session. "I want to make a difference, to be of some positive use," he says.
Marilyn Hanson calls herself "almost an original" who has participated in the weed-wacking effort since February 2001. "I get depressed watching exotic invasive species destroying natural habitat. This is my way of cleaning up a very small corner of the world and literally saving the desert from being choked by grasses," she says.
Following an informal "grass class" to help identify plants and explain removal methods, teams work in threes--a "digger," a "tugger" and a "bagger." One volunteer with a prybar will loosen the plant while another pulls the tufts out of the ground, and the third bags the invasive as refuse for the landfill. "The most effective way to get rid of the grass tufts is to enclose them in a plastic trash bag where the seeds get baked and sterilized before they get buried," says Hanson.
"We're removing clumps of buffelgrass that have been developing for 15-20 years, huge clumps that are firmly established," says Barbara Siegel, "and after four years, we're making significant progress toward being able to put away the digging bars. ... If we've been diligent in removing it properly, there is very little re-sprouting."
Think of these efforts, and a similar project in Sabino Canyon, as a prototype. "This whole concept is picking up steam," says Doug Siegel. "The Arizona Sonora Desert Museum is currently mapping buffelgrass infestations throughout the whole state of Arizona and in Sonora, south of the border, where solid stands of buffelgrass are smothering any other vegetation. This is a constant, hands-on, labor-intensive battle, but our numbers are increasing. The Pima Invasive Species Council and entities like the Sonoran Institute, Nature Conservancy, Forest Service, Fish and Game and environmental groups are enlisting in the battle. We're also trying to get buffelgrass entered into the noxious weed list, and then we can get some government funding for our efforts."
In the meantime, the Siegels (who met while digging grass and are now married) and their current cadre of weedwackers could use extra diggers, tuggers and baggers at the remaining 2004 sessions, Nov. 20th and Dec. 18th, starting at 8 a.m. Gloves, digging bars and trash bags are provided. If you'd like to participate, wear a hat and sturdy shoes, bring water and sunscreen and meet at the Caretakers House in Tucson Mountain Park on North Kinney Road across from the Desert Museum. Call 877-6122 to confirm your intent to participate--Doug needs to know how many homemade cookies to bake for snacks.