The “islands” in the middle Rio Grande through Albuquerque are really nothing more than sandbars that have stabilized because the river hasn’t flooded in years. But with this spring’s high flows they’re turning into an interesting little ecosystem experiment.
Back in the day, before dams and levies channelized the rio, it meandered a wide sandy flood plain, scouring things every few springs when things were wet. That hasn’t really happened for probably five decades. The winter of 1940-41 was a hugely wet year, causing major flooding, and the folks who lived here over the next several decades built a system to protect their homes and farmland. It was an understandable response, but the result is a human-mediated ecosystem that bears little resemblance to the old river.
The cottonwoods are a case in point. Along both sides of the river, the last cohort of cottonwoods is all roughly the same size and age – fifty years or more. Babies, which used to sprout following the spring scouring, are rare. But this year, on those phony islands in the river’s midst, scoured by a slightly larger-than-normal floodiing, baby cottonwoods can be seen.
I spotted some yesterday morning on the islands in the middle of the old Alameda bridge at the north end of town. I took mom and dad back yesterday evening for a look. They’re lovely, and it’ll be interesting to see how they do over time.
Update 6/23/05 Johnny_Mango got a closer look and thinks you can see previous years’ growth on the cottonwoods I thought were babies. I really need to track down a cottonwood subject matter expert and get more info.
