Saguaro cactuses are superstars of the Sonoran Desert | ECOVIEWS
President Teddy Roosevelt, the quintessential conservationist, said, "A grove of giant redwoods or sequoias should be kept just as we keep a great and beautiful cathedral.”
While in Tucson, Arizona, recently I was able to fully appreciate his sentiment. But not because of redwoods or sequoias or any other trees. The superstar of the Sonoran Desert is the saguaro cactus.
From a distance an observer might be forgiven for wondering why someone planted a line of slightly misshapen telephone poles. Upon closer inspection the poles reveal themselves to be the stems and arms of saguaro cactuses.
These upright plants sporting only a few limbs and no leaves dominate the landscape, and a close-up view is equally awesome. The plant itself has qualities as singular as those of the redwood, and each represents its state symbolically. The redwood is California’s state tree. The blossom of the saguaro is the state flower of Arizona.
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The largest member of the cactus family in North America, the saguaro cactus is the only species in its genus. No other species is closely related to this spectacular plant.
The human residents respect these impressive green giants of the Sonoran Desert. No one I met would dream of using one for target practice or harming a saguaro cactus in any way. A gun would more likely be turned on someone who violated the sanctity of the saguaro.
Like Arizonians, saguaro cacti may be armed. Many have one or two horizontal arms that bend and then grow vertically to create the classic captured-bandit pose. Some may have three or more arms.
The majority simply stand upright with no arms as it takes 50 to 75 years to grow the first one. Plants grow slowly in a desert. According to the National Park Service, “A saguaro grows between 1 and 1.5 inches in the first eight years of its life.” It takes at least 35 years to reach maturity.
A 50-foot-tall adult saguaro might be approaching 3 feet in diameter, weigh 6 tons and be 125 years old. The oldest, estimated to be more than 200 years old, would have germinated almost a century before Arizona became a state.
In much of the Sonoran Desert habitat, saguaro cactuses are the dominant plant, towering above mesquite trees, agaves and barrel cacti. The saguaro cactus has a critical role in the desert community. Gila woodpeckers and gilded flickers interact with the cactuses, the tallest vegetation around, like other woodpeckers do with pine trees. They look for insects and they excavate holes for their nests.
Other birds, including elf owls, the world’s smallest raptors, also make their nests in cactus holes. Harris hawks sometimes nest on saguaros with arms.
Saguaro typically bloom at night, and bats are one of their chief pollinators. Of course, the bats are not helping out the cactus just to be altruistic. The nectar of the saguaro cactus is quite rich in proteins. One scientific study found that the amino acids associated with the cactus pollen have a positive effect on lactation in some bat species.
Because most of the flowers are closed up during the day, the nectar is not depleted by diurnal birds and insects, which means it is available as a valuable nutrient source for the bats.
At Saguaro National Park in southern Arizona a decennial census calculates how many saguaro cactuses are present, as well as the size and age of resident plants. The census occurs in the same year as the U.S. census.
Since saguaro cacti do not move around and have no political agenda, a cactus population census is more accurate than a census of humans. In the previous estimate (2010), 1.6 million saguaro lived in the national park. The rough estimate for the 2020 census is that the numbers have increased to more than 2 million.
I feel certain President Roosevelt would want us to protect these icons of the desert just as we do redwoods and sequoias.
Whit Gibbons is professor of zoology and senior biologist at the University of Georgia’s Savannah River Ecology Laboratory. If you have an environmental question or comment, email ecoviews@gmail.com.
This article originally appeared on The Tuscaloosa News: ECOVIEWS | Saguaro cactuses are superstars of the Sonoran Desert
