Icon in Jeopardy

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.”

This article appears in Nov 5-11, 2009.