The Drought Diaries: Sad Sonoran

By Eilene Lyon

I’m spending this week on a solo camping trip at the Tucson Mountain Park, the largest county park in the U.S. at 60,000 acres. Here in southern Arizona, I’m on the eastern edge of the Sonoran Desert, which encompasses northwestern Sonora, Mexico, most of Baja, and a small section of southeastern California. The most notable endemic species of the Sonoran is the saguaro cactus. See a saguaro—you’re in the Sonoran.

Of the four American deserts, the Sonoran has the largest biodiversity and is the most heavily vegetated. The reason is the moisture regime. The Mojave, Chihuahuan, and Great Basin deserts all have a single rainy season, either winter or summer. The Sonoran is blessed with two rainy seasons, winter and summer. Though total annual moisture is just 12 inches, because it is distributed throughout the year, better living conditions exist for flora and fauna.

Like most of the Southwest, this area has been experiencing severe drought since the late 1990s. What I learned from volunteers at the Arizona-Sonora Desert Museum and Saguaro National Park, is that since September 2024 only a half-inch of rain has fallen.

By the first week in March, the desert should be awash in a rainbow of blossoms: sunny yellow brittlebush daisies, magenta lips of Parry penstemon, blue-purple desert lupine, gold-orange poppies. Outside of watered gardens, these are rarely seen.

Only the ocotillo is braving the conditions to bust out the scarlet nectar tubes so vital to migrating hummingbirds, but they’re foregoing the green leaves that usually appear this time of year. Even those stalwarts of the deserts, the cacti, are suffering.

The saguaros are still doing okay, at least here in the Tucson area. These plants are truly a wonder of nature. They have a taproot for stability, but for water absorption, they rely on horizontal roots a few inches below ground surface, spreading as wide as the cactus is tall.

Their interior structure is designed for water storage and a woody skeleton supports the weight of this water. A 20-foot cactus (perhaps 200 years old) can store a ton of water. A senior 40-footer: 2 tons of water. But don’t try to drink it! The cactus infuses it’s vital store with alkaloids that will make you dehydrate much quicker (from the emetic effects).

On our plant walk in Saguaro N.P., someone asked why the saguaros in Phoenix are dying. The volunteer explained that it has to do with photosynthesis, which the cacti do at night when the temperatures drop. But due to the urban heat-island effect, the nights are no longer cool enough in summer and they are starving as a result.

When you realize how difficult drought is here for the plants that all living things rely on, you can’t help but wonder why people think this is a place for large (and growing) population centers.

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