We need to avoid riparian hysteria
At a recent workshop on riparian ecosystems sponsored by the Tonto National Forest and Arizona Game and Fish Department, biologists dutifully presented their litanies on the inhabitants, histories and importance of steamside environments.
Although the theme of this symposium was understanding and not preservation, several speakers offered up the statistic du jour: 95 percent of the Southwest's riparian communities have been lost during a few centuries of human settlement. The prevailing attitude was that riparian communities are in such crisis that only extraordinary efforts might save the few forests remaining.
There's a danger in overstatement.
Scare tactics quickly lose impact, and in this case, a dire prognosis is misleading and focuses attention on the wrong priorities. The larger truth is that ecosystems are as temporary as we are. Conservationists need a victory from time to time to keep the juices flowing, and in the Southwest, most existing riparian communities can be considered victories.
My experience, from some 30 years as a field biologist in the Southwest, is that riparian vegetation has improved immensely since the 1960s and early 1970s. Entire forests of cottonwood and willows have sprung up where previously I saw only barren strands of gravel. Most of the mixed broadleaf forests that I monitor appear healthier than before. Sycamore and other deciduous tree saplings now populate stream channels in more than sufficient numbers to replace the parental giants that must fall before many more years have passed. Streams that formerly sank into cow-stomped sand now gurgle downward another 100 yards or more. Where earlier I saw the ravages of erosion and channel-cutting, I now see sediment rebuilding and healing banks.
These observations are not some trick of memory. Recent photos of Southwestern streamsides commonly show a marked thickening of gallery forests when compared to earlier photographs. The Hassayampa and Santa Maria rivers in west-central Arizona, Arivaca and Knipe ciénagas in southern Arizona, the rios San Pedro and Santa Cruz near the Mexican border, Animas Creek in New Mexico - all show signs of recent revitalization.
Why? Cattle, the bugaboo inhibiting reproduction by cottonwoods and willows, are fewer now at streamside as some ranchers try more enlightened management practices. Not a few streams and cienegas have been acquired by conservation organizations that protect them from grazing. The change in some of these communities can only be termed remarkable, and attests more to riparian resilience than frailty. Helpful, too, has been the ending of an era in which taxpayer dollars paid for stream channelization, clearing away water-loving plants, and other "water salvage" projects.
But the foremost factor has been climatic serendipity. Riparian forests are successional by evolutionary design and dynamic by nature. Comparatively short-lived and adapted to spring flooding, riparian trees were greatly handicapped by the dry winters that characterized the middle of the 20th century. Conversely, these relicts of the pre-Ice-Age world were uniquely positioned to take advantage of the bountiful runoffs that came in the springs of 1968, 1979-1981, 1983 and 1993. So great was the production of seedlings after these events that only the most intense cattle predation could negate the gains. Had it not been for the catastrophic summer floods that occurred in 1970, 1983, and locally in other years, our riparian forests would have attained even greater grandeur.
Now for the bad news
Unfortunately, rejuvenation of our streamside flora did little for native riparian fauna. Stream-dependent animals, from willow flycatchers to otters, are now absent from many Southwestern rivers, and nearly all of Arizona's native fishes face regional expiration if not extinction. Moreover, the problems confronting these native fish cannot be overcome by increasing streamflows or decreasing cattle-stocking rates. Nor can dams and groundwater-pumping - the usual culprits - always be blamed. Habitat loss is not always the simple cause of an animal's extinction.
What ails our aquatic animals is largely of the biologists' doing, and hence, difficult for them to acknowledge, much less resolve. One hundred years of translocating predatory game fish, live bait and bullfrogs have finally taken their toll. Mosquitofish replacing native Gila topminnows, red shiners replacing native minnows like the spikedace: Biologists were right there making it happen.
Of course, no one imagined that the consequences of introducing these aliens could be so damaging or the effects so long-lasting. Now in many ways it's too late. Eliminating spawn-inhaling channel cats, like preventing cowbirds from laying eggs in flycatcher nests, may not be feasible. Let's hope that agency fish biologists don't now embark on "remedies' as ineffectual and faddish as volunteers planting tiny cottonwoods.
David E. Brown, a former biologist for the Arizona Game and Fish Department, is now an adjunct professor of zoology at Arizona State University in Tempe.
