A Warming Climate Takes a Toll on the Vanishing Rio Grande

Meanwhile invasive Russian olive and tamarisk trees have moved in beneath the canopy, all fire-prone species. Fires in the bosque were once virtually nonexistent; now they routinely break out. In 2017, the Tiffany fire in southern New Mexico roared across the parched landscape, leaving more than 9,000 acres of riparian cottonwood forest a charred ruin.

Because of levees built to contain its flow, the Rio Grande now courses mostly through a narrow channel, rather than expanding broadly across the landscape, which disconnects the main stem from its many side channels. That has eliminated much of the meandering sloughs, braids, and oxbows, which are habitat for the silvery minnow, once present throughout the entire river but now found only in 10 percent of its range.

For some the answer to the existing problems with the Rio Grande is to restore some semblance of natural water flow.

“Optimizing the spring runoff is a really important strategy, because ecologically a whole bunch is tied to that,” said Paul Tashjian, director of freshwater conservation for Audubon Southwest. “The silvery minnow spawns during the pulse. Cottonwood seeds are flying during the pulse. Neotropical migrants are nesting during the pulse. If it happens a month earlier, it’s a misfire. It doesn’t provide those benefits.”

One strategy is to store water in reservoirs and allow it to be released at the right ecological time—easier said than done with so little water to go around, and most of it committed to farms and ranches.

Thomas Archdeacon is a US Fish and Wildlife Service fish biologist in Albuquerque charged with helping preserve the dwindling silvery minnow during a mega-drought. He and his colleagues placed window screens to capture silvery minnow eggs as they flowed downstream. They planned to take the eggs to a federal fish hatchery, where the fish are bred. But there were no eggs on the morning we visited.

Another fundamental problem is that low flows and irrigation cause the river to dry up in the summer, resulting in large-scale die-offs. “If 30 miles of river dries,” Archdeacon said, “it will kill all the fish.”

Come July, Archdeacon and others will rush out to the dwindling river and catch fish stranded in pools and take them below a nearby dam, where they can survive in deeper, cooler water for a while longer.

The increasing frequency and size of forest fires is also taking a toll on the Rio Grande. As we drove along the river near Santa Fe in early May, we could see giant clouds of smoke pouring out of the raging forest fires.

“After the Las Conchas fire [near Los Alamos in 2011] there were huge impacts on the Rio Grande,” said Allen. “It was an extreme fire, and it caused extreme flooding and debris flow. It added an incredible amount of sediment and turbidity, and it changed the chemistry and biota. The macroinvertebrates and fish were wiped out.”

An effort is ongoing in New Mexico to thin large tracts of forest to reduce the risk of major wildfires and prevent further fire damage to rivers.

Martin Baca has seen the changes firsthand. He was born and grew up on a family ranch along the river near Bosque, New Mexico, where he raises hay and bucking bulls for rodeos. He shows off a belt buckle the size of a bagel that he was awarded for high-quality bucking bulls. Normal, he said, seems to be over. “There has been less water for irrigating and a lot more wind,” he said. “You can irrigate, and five days later it’s dry. That hot wind is like a hair dryer. And there’s no dew. You need to have dew. It helps the grass grow. But you can’t get dew with that wind.”

“The climate is changing,” he said, pushing up the brim of his cowboy hat. “I didn’t believe it in the beginning, but I do now.”

Reporting for this article was supported by a grant from The Water Desk, an initiative based at the University of Colorado Boulder’s Center for Environmental Journalism.