Cacti Stage Comeback in Saguaro National Park

Some good news on a thorny issue: The saguaro cactus population, at least in Saguaro National Park, is soaring.

Park researchers have found a hefty increase in new plants over the past decade. They estimate that the total number has risen from less than a million to an estimated 1.62 million saguaros today.

But they caution that that doesn’t necessarily translate to similar gains all across southern Arizona. Factors ranging from invasion of exotic grasses to sprawling urbanization have had a damaging effect.

Park Supt. Frank Walker called the increase among small, young saguaros “just great news. However, continued monitoring will certainly be required.”

Researchers began a sampling study 10 years ago to determine the number of saguaros, which are found only in part of Arizona and in northern Mexico.

The stately saguaro can grow 50 feet tall and weigh a few tons or more, mostly stored water. It often will not flower before it is 50 years old or grow its first arm before 70. It can live for 200 years.

The researchers created 25 sampling plots, each nearly 10 acres in size, in the park’s eastern district and 20 more in the park’s western district.

Mark Holden, a Park Service biologist, said the estimate based on the sampling has a range of error of plus or minus 320,000 saguaros.

The study estimated that juvenile saguaros, from 4 inches to almost 20 inches tall, have increased by 125%. Many may have started in the early 1980s but were too small to be seen in the 1990 study.

“The saguaro is a very long-lived species, and to look at 10 years in the span of the population is just a snapshot,” Holden said. “This is something we’ll continue to have to study in the future.

“In general, the conditions for establishing saguaros are met probably just a couple of times a century, and it seems like there was a lot of doom and gloom predicted for the fate of the saguaro simply because we weren’t seeing new saguaros coming back in,” Holden said.

The younger population of saguaros have probably become established through a few years of more rainfall than average during 1980s and 1990s, Holden said.

Many deserts, and their saguaro populations, have disappeared in the maws of bulldozers expanding metropolitan Phoenix and Tucson.

And increasingly, exotic invasive grasses are crowding in around saguaros.