Vanishing Riparian Landscapes
Southwest Riparian Environments
by Jay W. Sharp
Late in the first millennium, Pueblo settlers began the process of clearing, modifying and polluting Southwestern rivers and streams and the riparian (or, bordering) woodlands, making way for a sedentary community life with villages, irrigated fields and commerce. Early in the third millennium, Euro-American settlers have very nearly finished the process, having profoundly altered an estimated 90 percent of the riparian landscape and having planned changes for much of the remaining 10 percent.
Before settlement, the Southwest riparian environments comprised the most diverse biological communities within the most biologically diverse region of the Unites States. The riparian systems endured relatively little damage at the hands of the Pueblos (whose total population probably never exceeded some 100,000), although the exhaustion of localized riparian resources and altered water flows probably helped force the abandonment of some villages. The systems have suffered far more at the hands of the Euro-American settlers (whose total Southwest population today equals roughly 7,000,000), especially during the last century and a half. Our riparian landscapes are now among the most threatened environmental systems in the entire U. S.
The Primal Riparian Systems
Spanish conquistadores found the Southwestern riparian systems mostly intact. Gaspar Perez de Villagra, chronicler of Juan de Onate’s expedition to establish the first European colony in the Southwest, spoke of the Rio Grandee’s "turbulent waters," "wide spreading trees," "grassy meadows," "countless birds" and "many fish" when the party struck the river just below today’s El Paso, following an agonizing passage north across the Chihuahua Desert in the spring of 1598.
Early Anglo-American explorers found many rivers and streams still in pristine condition at the mid-nineteenth century. "From the mouth of Bill Williams’ fork to the point above where we crossed the Rio Colorado, is about sixty miles " said Doctor J. M. Bigelow, who accompanied a railroad survey team across the Southwest in the 1850’s. "Along the valley of this river, alamo [cottonwood], mezquite, and willow form the principal, and almost entire, kinds of trees."
Free-flowing rivers and streams, with forested banks, issued from mountain ranges and wound through the arid Southwest basins like green threads woven through sand-colored tapestry. They supported long stretches of woodlands commanded by 60-foot tall Fremont cottonwood and willow trees and other stretches of park-like savannahs dominated by 60-foot tall mesquite trees.
They served as a cornucopia for Southwestern wildlife. For instance, they offered habitat, commissary and water to dozens of mammal species, ranging from shrews, pocket gophers, mice and rabbits to gray wolves, mountain lions, jaguars and grizzly bears. They sheltered hundreds of species of birds, both year-round residents and migratory visitors, including violet-crowned hummingbirds, thick billed parrots and ferruginous pygmy owls to great blue herons, ospreys and bald eagles. They harbored dozens of fish and amphibian species, including several which occurred nowhere else in the world.
Perhaps most importantly, the riparian systems knitted together varied biological strands which evolved in a region defined by its forested mountains and its sparsely vegetated desert basins. Their biodiversity, husbanding the genetic variability essential to help Southwest ecological systems adapt to changing environmental conditions, serves as a crucial gauge for the environmental health of the region.
The Southwest’s Great Drainage Systems
Most Southwest waterways connect either to the Rio Grande drainage system, on the eastern side of the Continental Divide, or to the Colorado River system, on the western side of the divide. The Rio Grande, which rises in the San Juan Mountains of southwestern Colorado, drains central New Mexico and all West Texas, a region of approximately 200,000 square miles (plus a comparable area in northeastern Mexico). Fed by a few perennial and many intermittent streams in the Southwest region, the Rio Grande flows nearly 1900 miles to the Gulf of Mexico. The Colorado River, with origins in the snowy mountain peaks of north central Colorado, drains western Colorado, southeastern Utah, southern Nevada, western New Mexico, virtually all Arizona, southeastern California plus southwestern Wyoming, an area of 430,000 square miles. Fed by six perennial tributary rivers and many intermittent streams, it flows approximately 1400 miles to the Gulf of California. Other, independent perennial and intermittent streams rise in mountains and foothills, their waters soaking into desert basin sands or evaporating into desert sky before reaching the major river systems.
The Roles of the Rivers
Collectively, the river systems and independent streams and their companion forests wander for thousands of miles across the arid Southwest. Although they blanket less than one percent of the region, they have performed the most vital of services for their neighboring plant and animal communities and for human settlers. First, the river and stream channels have conveyed that most important of all desert commodities water to sustain life and nurture growth and to recharge subsurface reservoirs. Their sandy soils have filtered sediments and nutrients to improve water quality. Their accumulated sediments have held water like a sponge, releasing it gradually, helping manage and prolong water flow during droughts. Their occasional floods, most often following spring thaws and the late summer rainy seasons, have stirred the biological pot, cutting new channels, distributing plant seeds, creating bottomland vegetational mosaics of forest, marsh and meadow. The forest canopies once shaded the water surface, cooling it, restraining evaporation, prolonging flow. Beaver dams once captured flood waters, trapped fresh alluvium, helped maintain water tables and encouraged riparian plant growth. River and forest game, fur bearers and fish once attracted hunters, trappers and anglers. Occasional fires swept the riparian woodlands, recycling nutrients, redefining vegetational patterns.
The Euro-American Settlers
When Euro-American settlers first arrived, they promptly began clearing the riparian woodlands, opening the bottomlands for communities, homesteads, roads, fields and pastures. They cut down the cottonwood and willow trees, using the timber to build towns, houses, furniture, barns, livestock pens and fences. They cut the mesquites from the savannahs, reducing the slow-burning wood to coke, a hotter burning fuel, which miners used for smelting gold and silver from nearby mines. They heavily stocked their new riparian pastures. They killed out predators, which threatened the livestock. They suppressed fires, which would have damaged property. They hunted riparian forests and fished the river waters, both for food and for sport.
As communities and agricultural enterprises grew, the Euro-Americans diverted water, via laterals and ditches, from rivers and streams to irrigate yards and fields. They drew water from the rivers and streams and from subsurface reservoirs to meet municipal, industrial and domestic requirements. They "channelized" rivers, forcing water flows to stay within banks. They delivered their waste into the rivers, counting on the flowing waters for disposal. They built dams to impound water, both to restrain flooding and to assure a steady supply. (One hundred large dams now impound Rio Grande system waters. Two hundred and sixty five large dams impound Colorado River system waters, all now used or lost before reaching the Gulf of California. A "large dam" stands at least 50 feet high or impounds at least a half cubic mile of water.)
The Euro-American settlers and their descendants, in an epic undertaking, have raised metropolises, homes, ranches, farms, parks and roads in the desert wilderness, vesting us today with a heritage built on legendary courage, hardship, sweat, integrity, sacrifice and heroism.
It comes, however, with consequences.
While municipal, industrial, domestic and agricultural demands for water continue relentlessly, river and stream flows and underground reservoirs decline relentlessly, with inevitable economic consequences. Excessive irrigation of poorly drained fields has left a legacy of waterlogged soils, salt, alkali and ruined thousands of acres of cropland in some areas. Channel cutting, promoted by denuded and severely overgrazed landscapes, intrudes into shallow water deposits and drains them, lowering the water table. Rivers and streams, no longer shaded by forest canopies, give up more of their water to the sky. Intrusive plants, especially salt cedar, command exclusive control of impoverished river and stream banks, hogging water and reducing biodiversity.
If they are to survive in the coming decades, communities dependent on dwindling rivers and falling underground reservoirs will not only have to implement aggressive conservation programs, they will also have to expand their reach for new water supplies, drilling deeper wells, extending pipelines, adding pumping facilities, desalinating water, reclaiming waste water, consuming increasingly expensive power, charging higher rates. They face the possibility of having to limit growth, which is especially difficult in cities like El Paso, Texas, where much of the population boom is attributable less to new arrivals from other states and countries than to high birth rates among current resident families. The communities face the potential of having to divert water from agricultural to municipal uses, which would mean that river bottom farming a centuries-old industry could decline or even collapse. They face the prospect of population displacements and economic restructuring.
The clearing of riparian forests and savannahs, the management of water flows, the depletion of water resources and the uncontrolled disposal of our cultural detritus has produced a litany of environmental consequences. For example, biodiversity the paramount standard for environmental health has withered. Fragmented remnants of native riparian vegetational systems no longer remain biologically interactive and mutually supportive. Barren and overgrazed stream banks, stripped of native vegetation, increasingly yield sediments into rivers and streams and stand as red carpets for the invasive species such as salt cedar and Russian olive. Spring and fall floods no longer disburse native plant seeds (such as the Fremont cottonwood), sculpt new vegetation mosaics, distribute new bottomland alluvium, nor recharge water reservoirs. Wildlife populations have declined. Species, their ranges shrunk and/or fouled, have become endangered or even extinct. Rivers, receiving unimpeded runoff from heavily fertilized fields, mine tailings, industrial and municipal waste, reek in some stretches with pollution.
Quality of Life Consequences
As our primal riparian landscapes fade across the Southwest, the wilderness experience becomes increasingly diluted for families who love camping and the outdoors. The wildlife community declines, to the dismay of those who love the birds, the mammals, the reptiles, the butterflies. Populations of game birds, animals and fish shrivel, frustrating hunters and anglers. Channelized flows, bare river and stream banks and trash-filled waters impoverish the soul. Every fall, we listen anxiously for the call of the Canadian and snow geese migrating southward ahead of the first cold front of the season, and we feel a sense of relief when we hear them.
Public Health Consequences
While economic costs mount, environmental systems suffer, and our quality of life declines, public health concerns increase. Near Moab, Utah, for example, ground water contaminated by more than 10 millions tons of uranium mill wastes is seeping into the Colorado River, threatening the drinking water of more than 20 million Americans. That threat is compounded by increasing salinity, which comprises chlorides, calcium sulfates, sodium, magnesium and potassium compounds. Similarly, increasing salinity threatens the Rio Grande’s water quality, which also suffers from municipal, industrial and agricultural runoff, a potential witch’s brew of human fecal mater, industrial trace metals, pesticides, herbicides and fertilizers. The threats increase downstream of major communities, for instance, El Paso and Juarez, which have a combined population well in excess of two million.
In Search of Balance
Our vanishing Southwestern riparian landscape raises fundamental questions which transcend individual issues such as the provision of municipal water supplies, the continuation of bottomland agriculture, the restoration of biosystem fragments, the preservation of an endangered species, the establishment of new wilderness parklands, or the purification and protection of water flows. The broader questions are:
- Do we have the will, the skills, the technology and the financial resources to manage our riparian systems, not just to solve isolated problems such as pollution by uranium mine tailings, but to assure our collective economic health, environmental health, emotional and spiritual health, and public health?
- Will national, state and local leadership emerge, not just with concerns for particular constituencies or individual situations, but with the broader vision and will necessary to answer a multifaceted challenge?
- Will our educational system develop programs, not as adjunctive, but as core curriculum to teach our children about the links between the economy, environmental sustainability, wilderness recreation and human welfare?
The Southwest, perhaps the most environmentally fragile of any large region in the U.S., still has the glory of its mountains, the solitude of its deserts, the magnificence of its sunsets, but its rivers and streams, its riparian landscapes, its biologically diverse lifelines stand on the precipice of collapse. We face hard decisions.
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