Saguaros endangered
Buffelgrass intensifies blazes, and it’s spreading fast in Sonoran Desert
Invasive buffelgrass that intensifies wildfires threatens cactus.
TUCSON — Early June 10, scientist Ben Wilder watched dozens of saguaros near Pima Canyon explode into flames as he stood in the Catalina Foothills. He had seen flames from the Bighorn Fire shooting down a mountain slope and up the sides of saguaro bodies.
“It was one of the most horrible things I’ve ever seen,” Wilder, director of Tumamoc Hill’s Desert Laboratory, told The Arizona Daily Star.
It will be a while before a saguaro death toll from this blaze is known. But Wilder on June 12 estimated that the fire took out as many as 2,000 saguaros, from both the front range of the Catalinas and the Pusch Ridge area near Oro Valley.
Some of those saguaros were amid stands of buffelgrass, an invasive grass that is known to spread and intensify wildfires to the point that they can burn saguaros that normally don’t burn. But the vast majority, maybe 75%, burned in higher-elevation grasslands, above where the buffelgrass has spread rapidly over the past 20 years across the Catalina Foothills, Wilder said.
In short, this was a near-miss for those like Wilder and other scientists who have long feared that the encroachment of buffelgrass into the Sonoran Desert would trigger extensive, destructive fires from which native desert plants would never recover.
The buffelgrass lying higher up, directly in the fire’s path, is “still fairly spotty,” Wilder said.
“It wasn’t continuous, wasn’t dense enough to be able to pull that fire all the way down, to make happen what we really fear,” Wilder said.
But he and other scientists remain concerned that if the buffelgrass keeps spreading without more controls, the next big blaze could cause more destruction and filter into the homes lying in the upper reaches of the Catalina Foothills — homes that this time were evacuated for a day and a half.
If the gap between the Catalina’s front range and the homes was like what it had been 20 to 30 years ago, when it was just Sonoran Desert vegetation, “we don’t have as many concerns. The desert doesn’t burn. That’s not the situation. The buffelgrass has come in. And if the area does burn, the desert will not come back, but the buffelgrass will,” Wilder said.
Buffelgrass areas in the Foothills have doubled in size every four to seven years.
“It would kill thousands and thousands of saguaros and paloverdes that would never come back. It would transform the desert scrub into a buffelgrass land.”
Aerial photos and maps show that buffelgrass areas in the Foothills have doubled every four to seven years, Wilder said.
Aaryn Olsson has studied buffelgrass for many years and done aerial buffelgrass mapping for the Arizona-Sonora Desert Museum. Olsson’s 2010 study found the buffelgrass areas were doubling at a slightly faster rate — every 2.26 to seven years.
“What’s happening is that it’s filling in the desert — it’s infill,” Wilder said. “The buffelgrass is not yet dense enough to carry the fire from the uplands into the desert, but it has exponentially grown.”
One area of disagreement is how much the buffelgrass impacted firefighting authorities’ decision to evacuate 200 homes in the Foothills from June 11-12 and then to evacuate homes farther north as the blaze moved toward them.
“Before buffelgrass, the houses were as close to at zero risk as we have,” Wilder said, adding that the presence of buffelgrass helped make the evacuations essential.
Coronado Forest Supervisor Kerwin Dewberry disagreed. While buffelgrass helped spread the fire, it was not just buffelgrass that took the fire so close to the Foothills.
“Fires happen all the time in various locations. Homes burn all the time with no buffelgrass. I don’t want to say just buffelgrass. It can be anything. If I narrowed it down to one species, it wouldn’t be true.”
Wilder, Olsson and Kim Franklin, a Desert Museum research scientist, hope this fire will be a wake-up call that prompts more government action to rid the area of the buffelgrass by manually pulling it out or by spraying more herbicide.
Scientists have been warning of the dangers of buffelgrass invading the desert for many decades. “The extent of the problem at this point requires much more resources than the Forest Service can throw at it,” Franklin. She hopes that by the end of the year she will have come up with a price tag for removing the Catalinas’ buffelgrass.
Controlling buffelgrass is going to be something like road maintenance that has to be done every year unless there is a longer-term effort, Franklin said.
“There has not been the societal or political will to address this threat,” Wilder said. “It’s been expanding at an unchecked rate. There have been a lot of efforts to combat this, but they haven’t met the challenge.”
Coronado National Forest officials treat 1,000 to 2,000 acres of buffelgrass in the Catalinas annually with the herbicide glyphosate, more commonly known as Roundup. “We are going to continue to make the efforts we have in place. We will continue to do that ... as we have funding to do so,” Dewberry said.