News
General Interest
Battling Buffelgrass
October 12, 2006
By Stephanie Doster
Julio Betancourt (left) and Travis Bean (right) on Tumamoc Hill.
Credit: Stephanie Doster
Imagine hot fires that routinely race along roadways and rip into open space around Tucson, Arizona, fueled by dense, dry buffelgrass stands that seem to double every year.
An untold number of saguaro-the icon of southern Arizona-would succumb. Cholla, ocotillo, barrel cactus, and palo verde trees that had managed to compete with the grass would be additional casualties. Cactus wrens, pygmy owls, and other animals that rely on desert plants would disappear, as would the spring wildflowers and the yellow brittle bush blossoms. So would the tourists who flock to the Old Pueblo for its sun and unrivaled biodiversity. As houses burn in badly-infested areas, property values would surely plummet. There are sure to be some human casualties in these fires.
That catastrophic scenario is one that The University of Arizona researchers fear will happen as buffelgrass and other invasive grasses, combined with climate change, break down ecosystems that are ill-adapted to flame. The buffelgrass invasion in southern Arizona is another unintended impact of government-sponsored programs to introduce new plant materials for land reclamation and to establish grass in the desert for cattle, said Julio Betancourt, adjunct professor in Geosciences, Geography and Regional Development, and the Laboratory of Tree Ring Research with The University of Arizona Desert Laboratory on Tumamoc Hill in Tucson. These programs failed to anticipate the growing importance of tourism and urbanization in the regional economy, which will be compromised by increasing fires, he said.
"Buffelgrass will be the unhinging of the Sonoran Desert. It's not something we have any doubts about. It's here and now," said Betancourt, who also is a senior scientist with the U.S. Geological Survey. "There won't be much diversity left."
Invasive species tend to crowd out and out-compete native plants, and some like buffelgrass carry fire easily and then resprout to hold their ground. Native plants rarely survive the fires and have a difficult time reestablishing in the thick grass.
"Buffelgrass stands lead to the loss of woody and succulent life forms because of fire. They fill the inner spaces between plants and can carry fire from one island of shrub to the next one," said Travis Huxman, a UA professor of ecology and evolutionary biology who, with J. Alex Eilts, one of his doctoral students, has studied how buffelgrass out-competes other plants for water. "In the savannah areas, fire has evolved with the system. But in the lower-elevation arid part, fire has not evolved with the system and the plants can't handle fire."
In an effort to prevent this from happening, staff and students on Tumamoc Hill have sprayed herbicide on individual buffelgrass stands, leaving dead brown mats of the plant on the rocky slopes. The workers have a short window-only five to ten days-when the buffelgrass is green and can be sprayed and killed. Other buffelgrass eradication and education programs also are underway: the Sonoran Desert Weedwackers are yanking and digging the grasses up in the Tucson Mountains and the Arizona-Sonora Desert Museum is mapping buffelgrass distribution.
Betancourt said eradicating the grass is possible, but only with the cooperation and a commitment at every level of the community. At the most local level, homeowners can pull buffelgrass out of their yards and neighborhood associations can clear it from along side roadways to prevent its spread to natural areas.
First introduced in the area as a soil stabilizer in 1938, the African buffelgrass has efficiently filled in natural spaces between native plants, crowding out and out-competing the natives by slurping up available water before other plants do. In 1983, researchers found the grass in only five or six spots on Tumamoc Hill. Now, Betancourt said, it covers 40 percent of the research site's 865 acres; in the past year, the number of buffelgrass stands has doubled, if not tripled, he said.
"It's a microcosm of what's happening throughout the Sonoran Desert, including Baja California," said Betancourt, who has played a key role in reconstructing the long-term vegetation and climate history of the North and South American deserts.
The number of buffelgrass stands has exploded in the past decade for a number of reasons, Betancourt said, including increasingly fewer freezes, which are the main limit to this frost-sensitive tropical grass. The protracted drought in the region, following some of the wettest decades on record, has also exacerbated the situation, rendering some of the less competitive native plants vulnerable. Drier conditions, combined with warmer temperatures, have "lifted the lid off of buffelgrass," Betancourt said.
Travis Bean, coordinator for the buffelgrass education and control project on Tumamoc Hill, said about half of the smaller shrubs and native grasses are eliminated by the presence of buffelgrass stands-and that's before flames tear through the area. The grass dries out and remains highly flammable for about 10 months of the year, Bean said. The first known buffelgrass fire, sometimes mistakenly called a brush fire, was the Duval Mine Fire in February 2004, Betancourt said. In November 2005, a fire fueled by the grass claimed the life of a homeless man near Davis-Monthan Air Force Base.
"The burnable stands along the roads and in neighborhoods are a threat to life and property," Bean said. "They're not something you really want growing under the eaves of your house."