Monsoon rains also supply about 25 percent of the groundwater recharge that feeds this area’s aquifer. The aquifer is heavily used for drinking water in Tucson’s suburbs such as Oro Valley, Green Valley and Marana and by private well owners in unincorporated suburban areas.

Tucson relies mostly on Colorado River water for drinking. But the aquifer will serve as a backup supply for Tucson in the event of a Colorado River shortage.

Also, monsoons are critical for forests, wildlife and rangeland health in the mountain highlands and grasslands, where summer rains trigger much of the plant growth and productivity, Meixner said.

Monsoons also are important for maintaining urban and residential greenery in particular, he noted.

If you want to see how the Sonoran Desert surrounding Tucson after a century of declining monsoon rains would look, just drive west to the Gila Bend area, which currently gets 30 to 40 percent less monsoon rains than we do, said Mark Dimmitt, a retired Arizona-Sonora Desert Museum scientist.

“About half of (this) region’s plant species are adapted to respond primarily to summer rains. Densities of many species would decline significantly, and numerous others would die out here altogether,” said Dimmitt, who also wasn’t involved in the study.