By New Times
By Connor Radnovich
By Robrt L. Pela and Amy Silverman
By Ray Stern
By Keegan Hamilton
By Matthew Hendley
By Monica Alonzo
By Monica Alonzo
Despite what you might have heard or read, the giant saguaro cactus is not dying off. There are plenty of genuinely endangered environmental victims around this big, bad world, but Carnegiea gigantea isn't one of them.
McAuliffe reviewed more than 50 years of research and management techniques at Saguaro National Monument. His report, a critique of essentially all of the most significant scientific work ever done on the saguaro cactus, lays waste to a lot of it as "bad science," and contradicts the prevailing notion that the saguaro cactus is doomed to extinction. "I'm always getting calls from Newsweek reporters, or the New York Times, saying, 'We've heard the saguaros are dying,'" says McAuliffe, who taught at the universities of Arizona and Nevada-Las Vegas before joining the botanical-garden staff three years ago. "One day it's disease. The next day I get a call saying, 'We've heard that the growing ozone hole is causing the saguaros to disappear.'
"Mistakes in saguaro research have created so much misunderstanding, I think the only way to cure it is to start swinging a hatchet." McAuliffe targets research done at the monument, founded near Tucson in 1933 to protect and showcase what was then an awesome stand of mature, multilimbed saguaros. It was a spectacular "cactus forest" unlike any other in the Sonoran Desert in Arizona and Mexico, the plant's only natural habitat.
To date, a majority of that research has been focused on one disturbing trend: Saguaro National Monument's population of big saguaros has been visibly declining for more than 50 years. Worse, the dying saguaros have not immediately been replaced with other equally impressive plants. Of course, saguaros and the concept of "immediately" don't mix: The life span of a healthy saguaro is more than 150 years. Five-year-old plants are about the size of a human thumbnail, and the cactus doesn't begin to reproduce until about age 50 or sprout arms until about age 65. In most saguaro experiments, the subject outlives the scientist, and research started this decade will only begin to have much relevance in about 2100. As the monument's older saguaros have gradually dropped dead, the aesthetic effect has been devastating: Sequential photographs dating to the 1930s appear to illustrate a mass extinction.
McAuliffe swings his hatchet most forcefully at early researchers who blamed the apparent die-off on a mysterious bacterial disease, and later scientists who tried to blame more contemporary environmental woes. Their theories and resulting experiments, he says, were poorly conceived and executed, yet received inordinate publicity.
And the public, already prone to overromanticize the plight of the saguaro, has been misled about the plant's true status, which is, McAuliffe says, actually quite healthy. "Unfortunately, the worst research always gets put up on the tallest pedestal," he says. @rule:
@body:The first bad round of research, McAuliffe says, resulted in the misdiagnosis of a deadly saguaro mystery disease in the late 1930s and early 1940s, about the same time that the saguaro ranks were beginning to thin. That's when a scientist from the UofA decided that the big cactuses were dying because of a "blackening necrosis"--a trunk discoloration that eventually turned to rot--caused by the bacterium Erwinia carnegieana. This theory prompted years of "disease suppression experiments" at the monument. In one test, affected plants in a 320-acre area were removed (by dragging them out of the ground using cables attached to trucks), disinfected with chemicals including kerosene, then buried in a mass grave. In other experiments, antibiotic treatments were applied to the sick saguaros, which were also doused with pesticides after it was discovered that a species of moth was spreading the "disease."
By the early 1960s, researchers who followed up on the preliminary disease work were predicting that the monument's saguaro forest would be wiped out by the turn of the century.
Nuts, McAuliffe concludes: The disease hits cactuses that have already been damaged by cold weather. The midcentury die-off of mature, many-armed saguaros--the seeming catastrophe that prompted so much concern--was actually caused by a hard freeze in 1937. Saguaros are most vulnerable to weather extremes when they're either very young or very old. Many of the big plants that made up the Cactus Forest in 1940 had sprouted during the mid- to late-1880s--due to extra-heavy rainfall, a meteorologically sublime time for young saguaros--and managed to survive a severe freeze in 1913 because they were then in their sturdy years of late middle age. But the big chill of 37 nipped them, then the bacteria went to work, McAuliffe asserts. Subsequently, scientists spent decades battling a plant disease that struck saguaros that were already dying. And deep freezes near the turn of the century explain why so few mature cactuses are with us now: They didn't make it out of puberty. @rule:
@body:Some contemporary research at the monument has been no more enlightened than the earlier black-tissue work, according to McAuliffe, who is critical of recent experiments done by the National Park Service's Denver-based Air Quality Division.