River flows provide vital lifeline through parched valley
When water in the Rio Grande was unexpectedly released in March, two months earlier than in recent years, I was relieved that the riverbed and surrounding water table would be replenished again – and especially so, given the severe to extreme drought conditions we in southern New Mexico have long been experiencing. Daring some cautious optimism, I also hoped that the increased moisture would have tangible benefits for the riverside vegetation and the many birds and pollinators that depend upon those habitats.
With a fully flowing river, the moisture in the surrounding floodplain nourishes not only the native willows and other trees growing alongside the river, but also the many layers of shrubs and wildflowers that break dormancy and emerge in the floodplain and beyond. These plants, in turn, support countless insects and other invertebrates, which then provide vital fodder for a great many species of migrating and breeding birds.
This complex web of life associated with the river is a major reason why the Rio Grande has been such an important migratory corridor through the ages. Its north-south track and historically perennial flows through what is known as the Central Flyway have made it a verdant ribbon through the desert, and during times of prolonged drought an especially critical lifeline.
Over millennia the Rio’s course has shifted and seasonal flows have varied, depending on snow melt and monsoonal rains, but its importance as an ecosystem hasn’t wavered – even in the last century when much of our stretch of river has been diverted and channeled into concrete ditches. The natural reaches, to the extent that they remain and are allowed to go unmanaged and unmown, continue to provide essential habitat for myriad creatures.
When the water flow is “turned off” at Elephant Butte and the riverbed goes dry, much of that network of life slowly depletes as well, and although some organisms may be able to bide their time indefinitely until the water is “turned back on,” many others struggle or succumb. I have a feeling that such was the case the two previous spring seasons, when the Rio went dry for eight months, with no flow until late May.
The dry riverbed during spring migration those years undoubtedly discouraged some of the more sensitive, river-associated bird species from breeding. Both yellow-billed cuckoos and Bell’s vireos, both of which were regular breeders along a nearby stretch of river in past years, were scarce or not detected at all those two summers and, as species that are entirely insect-eaters, it’s likely that the desiccated vegetation was a factor.
This year, the corridor is now a much healthier green, thanks to the early water release. Even so, the Bell’s vireos haven’t reappeared and the very low hummingbird numbers continue to be worrisome, unfortunately, but we have recently heard a cuckoo calling in the neighborhood several times, so I’m holding out hope that they’ll return to breed once again.
In the meantime, I continue to question the wisdom of tweaking our great river as much as we do, expecting that we can turn it on and off at will and not suffer consequences. There’s a thoughtful and beautifully done film that explores the Rio’s many historical and cultural uses and current challenges, “Requiem for a River,” by Mary Patierno, that will be screened on Wednesday, June 26th, 6:00-8:30pm, at NMSU’s Domenici Hall, Room 106. Its creator plans to participate (remotely) in a community discussion following the screening.
Marcy Scott is a local birder, botanizer, and author of "Hummingbird Plants of the Southwest." Along with her husband, Jimmy Zabriskie, she operates Robledo Vista Nursery in the North Valley, www.robledovista.com, specializing in native and adapted plants for birds and wildlife habitat. She can be reached at HummingbirdPlantsSW@gmail.com.
This article originally appeared on Las Cruces Sun-News: River flows provide vital lifeline through parched valley
