by Leo W. Banks
Tucson Weekly
The continuing spread of buffelgrass could lead to the disappearance of our great saguaro. (Courtesy of Saguaro National Park)
Buffelgrass is forcing us to think the unthinkable: A Sonoran Desert in which the saguaro cactus is no longer the master of the landscape.
Is this really possible? Could Arizona's cherished icon vanish from a substantial portion of its range?
Actually, yes. The problem is fire.
The Nature Conservancy biologist Dale Turner says the density and distribution of buffelgrass is increasing dramatically, and in those places where it becomes the dominant plant, the number of fires will increase.
"That means every other plant that's both slow-growing and fire-sensitive will disappear," says Turner. "That's certainly the saguaro. I don't think it will go extinct, but we'll see saguaro populations either lost or seriously degraded."
Prior to buffelgrass, fire was never a major player in the Sonoran Desert. Old-fashioned fires—if we can use that term—didn't burn too hot or too long, because native grasses don't have the biomass to create big blazes.
Buffelgrass does, and it won't pause to catch its breath after a fire. It regenerates quickly and thicker than before, making subsequent blazes more intense, with plenty of fuel to run across entire valleys and up grassy slopes.
The result is greater destruction for small cacti, especially in lower desert areas, says scientist Bill Peachey, who manages saguaro study plots at Colossal Cave Mountain Park. "A buffelgrass fire kills baby saguaros and all the small cacti, and you're fooled, because you might still see large saguaros on rocky hillsides," says Peachey. "But the fire has chopped out a whole segment of the reproductive cycle."
After a blaze, saguaros might take 50 to 70 years to start reproducing again. If all the saguaros present at one time die, the area will almost certainly burn again before new plants can grow to replace the old ones.
Imagine looking at the desert floor west of Gates Pass, in the Tucson Mountains, and seeing the once-grand saguaro forest looking anemic and uninspiring. Imagine the tourism industry trying to sell Arizona as a destination without as many photos of the mighty saguaros standing tall against a blazing sunset.
But let's not move too fast. Over the decades, there have been several periods in which scientists have falsely predicted the saguaro's doom, and it hasn't happened. So not only has history taught us humility; it has proven the saguaro to be a master of survival in a harsh environment.
Still, Turner and Peachey aren't alone in sounding the alarm. The Weekly interviewed five scientists, and they all agree on one thing: The desert of the future will have much more buffelgrass and fewer saguaros.
The spread of this African perennial grass, which was introduced to the region in the 1930s and 1940s as forage for cattle, is happening with alarming speed.
At Saguaro National Park, the acreage containing buffelgrass is expanding 35 percent per year, says Meg Weesner, the park's director of science. It existed on 175 acres in 2002. Today, it grows on 2,000 acres, and one prediction has it infesting 10,000 acres in a decade. That's a significant portion of the park land on which saguaros grow.
If uncontrolled, buffelgrass could completely alter the park's habitat and eliminate saguaros from certain areas. "Our future might be a grassland of African grass instead of what we now know of as the plants and animals of the Sonora Desert," says Weesner.
Buffelgrass has gained such a foothold in Southern Arizona that stopping its spread is now impossible. Ranchers across the border in Sonora, Mexico, actually have been planting the grass for about three decades, and that has made it inevitable that buffelgrass seeds would cross the line, too—on the clothes of illegal aliens, on the tires of smuggler vehicles that cross our protected deserts, and even on the feathers of birds and on the wind.
Tucson botanist Matt Johnson, who has been studying desert environments for 30 years, says eradication efforts, such as the county's new aerial-spraying program in Tucson Mountain Park, offer some encouragement. And he's heartened by volunteers who go into the desert to remove buffelgrass stands.
"But it'd require half the population of Tucson turning out on a semi-regular basis to get rid of it all," says Johnson.
The most realistic hopes rest on keeping buffelgrass out of certain areas. This requires workers going into these areas multiple times to pull the plants, then returning after heavy rains to treat buffelgrass seedlings that continue to sprout.
Weesner says these efforts have worked in parts of Saguaro National Park, but it requires a lot of work, done quickly, to stay ahead of the spread.
But the spread is inevitable. And it might mean the saguaro is entering a period of significant decline that can't be altered. The hardest-hit areas will likely be in the wettest portions of the saguaro's range, in the northern and eastern Sonoran Desert. In Arizona, that means around Tucson, San Manuel and Florence, and up to Wickenburg in the north.
All of this leaves Johnson, a reluctant pessimist, thinking out loud about some yet unknown feat of bioengineering that could put buffelgrass in its place. By that, he means the creation of some pathogen or insect that could attack buffelgrass and eliminate it.
But he says that's more in the realm of science fiction, and he worries that such a creation could become uncontrollable and go after native range grasses, or perhaps migrate to the Midwest and destroy corn and wheat crops.
"Remember Jeff Goldblum's character in Jurassic Park and his line, 'Nature will find a way'?" says Johnson. "We've never had much success with that kind of bioengineering, and my concern is we're not yet able to engineer something to keep a disaster like that from happening."