Ciénega de Flores

A ciénega (also spelled ciénaga) is a wetland system unique to the American Southwest. Ciénagas are alkaline, freshwater, spongy, wet meadows with shallow-gradient, permanently saturated soils in otherwise arid landscapes that often occupy nearly the entire widths of valley bottoms. That description satisfies historic, pre-damaged ciénagas, although few can be described that way now. Incised ciénagas are common today. Ciénagas are usually associated with seeps or springs, found in canyon headwaters or along margins of streams. Ciénagas often occur because the geomorphology forces water to the surface, over large areas, not merely through a single pool or channel. In a healthy ciénaga, water slowly migrates through long, wide-scale mats of thick, sponge-like wetland sod. Ciénaga soils are squishy, permanently saturated, highly organic, black in color or anaerobic. Highly adapted sedges, rushes and reeds are the dominant plants, with succession plants— Goodding's willow, Fremont cottonwoods and scattered Arizona walnuts—found on drier margins, down-valley in healthy ciénagas where water goes underground or along the banks of incised ciénagas.

Ciénagas are not considered true swamps due to their lack of trees, which will drown in historic ciénagas. However, trees do grow in many damaged or drained ciénagas, making the distinction less clear.

Current state

Undamaged ciénagas, essentially nonexistent today, were characterized by a slow-moving, broad flow through extensive emergent vegetation as just described. But today, the ongoing region-wide erosion that followed the arrival of Europeans in the American Southwest and the subsequent alteration of the land by settlers firmly entrenched water flow between vertical walls, resulting in an ever-worsening incision process, a drawdown of local water tables and the drying up of most marshland environments, leaving behind scarcely few undamaged ciénagas. Many that remain today look and function like a creek: narrow, incised and continuing to degrade. "Since the late 1800s, natural wetlands in arid and semi-arid desert grasslands of the American Southwest and Northern Mexico have largely disappeared."
File:San Solomon Ciénega.jpg, San Solomon Spring-fed ciénega, near Balmorhea, is in arid West Texas. The springs have a tremendous flow of 22 to 28 million gallons a day. (2009)
File:1 - Healthy Cloverdale Cienaga.jpg, Cloverdale Ciénega in the Bootheel area of southwest New Mexico. This illustrates what an undamaged ciénaga looks like under normal conditions: marsh-like, broad, shallow, slow migrating water through thick vegetation. (2008)
File:1.5 Healthy Slightly Incised.jpg, Cienequita, Las Ciénegas, north of Tucson, Arizona. With very little incising, this is a smaller, functioning ciénaga. (2012)
File:2- Healthy Cienaga after Flood.jpg, Canelo Hills, Arizona. This is what a healthy ciénaga looks like after a flood, erosion is avoided by plants that lie down and spring back after heavy flows. (2009)
File:3 - Incised Cienaga-crop.jpg, Burro Ciénaga on the Pitchfork Ranch south of Silver City, New Mexico. Today, many of the few remaining ciénagas that still have water look like this, deeply incised by fast flowing water trapped between vertical walls. (2005)
File:4 - Narrow Incised Cienaga.jpg, Burro Ciénaga down channel about a quarter mile from the previous photograph. This section is more severely incised and creek-like: narrow rather than wide enough to cover the entire valley floor, historically reaching the toes of the canyon on both sides. (2006)
File:5 - Dead Cienaga.jpg, Former San Simon Ciénega on the Arizona/New Mexico Border. Now dead, this ciénaga is beyond any possible recovery due to serious water overdraft, despite determined, long-term government effort. (2010)

Properties

Ciénegas occur at intermediate elevations (1000-2000 m) and are characterized by saturated, reducing soils with reliable water supply via seepage. Sedges, rushes, and grasses are the dominant plants, with a few trees that can withstand saturated soils, such as willows. Ciénegas trap organic matter from their surroundings, and are thus highly productive ecosystems.

The structure of a natural ciénega is influenced by long-term climatic cycles of wet and dry periods. During dry periods, falling water tables lead to a reduction in vegetation. Prolonged wet periods lead to increased vegetation and trapping of sediment, while brief periods of high rainfall may lead to carving of gullies. Runaway gully growth, as can occur when vegetation is artificially removed (e.g., by overgrazing), can lead to channelization and loss of the ciénega.

Importance and conservation

As a primary source of water in arid environments, ciénegas support a broad range of terrestrial life, including numerous endangered species. For instance, in Arizona, 19% of threatened, endangered, or candidate threatened or endangered species are directly associated with ciénegas. Ciénegas also purify surface water and mitigate flooding when heavy precipitation occurs, and help to cycle nutrients between water and soil. Humans have also long relied on the water provided by ciénegas: Indigenous Americans used ciénegas for water and hunting grounds, and a majority of pre-historic agricultural settlements occurred in the vicinity of ciénegas. Indigenous inhabitants of the American Southwest also gave spiritual significance to ciénegas and local watering holes.

The decline of ciénegas has been caused largely by changes in land use, primarily overgrazing (which removes water-absorbing vegetation) and overexploitation of ground water for agriculture and urban use. Direct removal of vegetation from the vicinity of wetlands has also been a cause of ciénega loss, as has the extirpation of beaver from the region. Preservation of existing ciénegas, and restoration of degraded ciénegas, depends on reversing these trends in land use and preventing their recurrence in the vicinity of ciénegas. This preservation is complicated by the fact that a majority of ciénegas are found on privately-owned land, most of which do not have binding conservation agreements or easements in place.

Occurrence

It is likely that there were many hundreds of long lost ciénagas when the Southwest was Indian country, although there are only 155 identified or named ciénagas since the European arrival in the entire International Four Corners Region of the Southwest — that is, Arizona and New Mexico in the United States and Chihuahua and Sonora in Mexico. As shown in Table 2 below, fewer than half (44%) of known ciénagas are functional or restorable, while 56% have no potential for restoration or are dead.

In late 2018, as part of his effort to create a wetland action plan for the state of New Mexico, retired former New Mexico botanist Robert Sivinski discovered via satellite an additional 119 small ciénagas in New Mexico. This surprising number of previously unidentified or unstudied ciénagas suggests there may be more to be found. A working ciénaga inventory is maintained at the University of Texas Austin with access to numerous papers, google maps and other ciénaga materials

See also

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References

{{DEFAULTSORT:Cienega
Topography
Wetlands
Springs (hydrology)