Along New Mexico’s Rio Grande Midstream, Bosque is the largest cottonwood forest in the country, stretching nearly 200 miles throughout New Mexico.
Cottonwood seeds fly through the air on white, cottony puffs (hence the name).
The 1941 flood washed large amounts of sediment into the Rio Grande, creating a fertile bed for the beginning of the Bosque.. But the flood also destroyed farms and towns. In the 1960s, construction progressed on the massive Cochiti Dam, 50 miles north of Albuquerque, to block the flow of water and sediment down the river. It worked — at a cost.
The dam also stopped the flood pulsation. This prevented the young poplars from establishing themselves, leaving only the 80-year-old trees that grew after the flood. Craig Allen, a former ecologist with the U.S. Geological Survey and a resident of Santa Fe, New Mexico, calls it a “zombie forest.”
“It’s a living corpse,” he said. “Entire riverbank systems have turned drier.” Invasive fire-prone tree species such as tamarisk have moved under older cottonwoods. Once unheard of, Bosque forest fires are commonplace.
Dams are also used to intercept gravel, silt, and other sediments carried by rivers and to build new ecological features during floods. The fine sediments trapped behind dams contain essential nutrients, “undermining the base of the food chain,” says Matt Condorf, a professor of environmental planning at the University of California, Berkeley. increase.
The dams also reduce the flow of rivers, “simplifying the waterways,” he said. “So all the places that used to have gravel beds, pools and streams are washed away and end up in the shape of a bowling alley.