Cuatro Cienegas Oasis and 70+ Endemic Species Bound for Extinction

Evan Carson, a biologist at the University of New Mexico who specializes in the evolution genetics of desert fish, has been conducting research in the the Cuatro Cienegas Basin in the north of Mexico since 1998. He refers to this pocket of unique bio-diversity as being, “without question, one of the most remarkable natural systems on Earth.” The pools, springs, and rivers of the Cuatro Cienegas Basin give life to an ecosystem that does not have a compliment anywhere else in this world.

Read more on EnviroChronicle: Cuatro Cienegas ecosystem here

But this oasis ecosystem in the middle of the Chihuahuan desert, which has survived in some form since the time of Pangaea, is on the verge of dying in the time of man. The rapid decline of water levels in the spring fed pools and streams have lead Carson to conclude that the aquifers, which breath life into the bio-diversity here, are being sucked dry by large scale agricultural exploitation in the surrounding valleys. The entire Cuatro Cienegas ecosystem appears to be on the verge of collapse, with some of the pools having already dried up. The fear is that this trend will continue, and that the pools, the 70+ unique species of fish, snails, and reptiles, along with bacterial mats — life forms that scientists have only just begun to gauge the importance of — will disappear within the next few years.

Evan Carson provides vagabondjourney.com with a deeper look into what may be the last days of this remarkable ecosystems in the following interview:

Could you provide us with a quick summary of the ecosystem in the Cuatro Ciénegas area and what makes it unique in the world? What do we stand to lose if the reserve dries up and dies? 

The Cuatro Cienegas basin is composed of a great variety of springs, rivers and streams, as well as marshes, lagunas, small pools, and various habitats at habitat margins and interfaces. These habitats range from large to small (for springs, rivers, marshes, and lagunas) and span an environmental gradient that includes springs that are temporally stable (over seasons and years) to marsh, laguna, and peripheral habitats that exhibit large and often severe fluctuations in temperature, salinity, and water level. The latter habitats can fluctuate dramatically over hours in temperature and over days to weeks in salinity, temperature, and water level. The most stable habitats generally occur in upper reaches of each system and tend to have a diverse aquatic fauna, including numerous fish and hydrobiid snail species, more than half of which are endemic and almost all the rest native. The environmentally severe habitats occur farther downstream, especially at the terminus of each system. These habitats are home to very few fish and snail species, but the fishes found there can be highly abundant. These fishes also experience natural boom-bust population cycles, often directly related to natural, seasonal drying of the habitat. Intermediate habitats connect the source and terminal habitats, and they host an intermediate number of fish and snail species.

There are 16 fishes historically associated with the basin, at least nine of which are endemic. These include species from various regions and families. Similarly, bacterial diversity is extreme, though this is probably the case in several spots around the world. The hydrobiid snail fauna is mostly endemic and includes many species. Part of what makes Cuatro Cienegas unique is that it not only contains so many endemic species, but within each of these groups (snails, fishes, bacteria, etc.) the endemic species are represented by a relatively diverse combination of evolutionary lineages. Few places in the world can boast of such a concentrated and diverse level of endemism. While this is remarkable, it also places the fauna at tremendous risk because the basin is small enough that all habitats could be lost fairly easily and quickly, as appears to be happening.

Cuatro Cienegas map

If these species and habitats are driven to demise, the loss will be
twofold. The obvious loss is to biodiversity. Mexico is fortunate to possess such a biologically valuable resource. However, it also is at great risk of losing one of the more special places on Earth and this loss would be especially severe in terms of regional biodiversity. Less talked about, though, is that loss of the water resources in the valley would also be severe for the people of Cuatro Cienegas. The town depends on water for its economic prosperity. If you have ever been to Cuatro Cienegas, you might be tempted to think it is a rather poor place. But if you also visited the neighboring towns of Sacramento and Nadadores, neither of which have meaningful water resources, you would have seen where the Town of Cuatro Cienegas could be headed. Without water, Cuatro Cienegas will be just another dusty, poor, depopulated town in the middle of the Chihuahuan desert. Cuatro Cienegas has a lot of history, including being the birthplace of Venustiano Carranza, a leader in the Mexican Revolution and a former President of Mexico. So, yes, loss of the aquatic habitats in Cuatro Cienegas would ultimately come at a social and economic cost locally, but the larger effects would also be cultural. I suspect many Mexicans throughout the country would come to regret and feel shame over loss of the Biodiversity of Cuatro Cienegas, in part because it is not only unique habitats and species that are at stake.

Introduced aquatic animals, so far as is known to me, include only one snail (the Malaysian Melanoides tuberculata.) and a handful of fishes (common carp Cyprinus carpio, blue tilapia Oreochomis aureus, the jewel cichlid Hemichromis guttatus, and Florida Bass Micropterus floridianus). The jewel cichlid is far and away the most problematic, as it is tremendously abundant in several places and appears to compete with native species; the others are uncommon or rather confined (for now at least), though the bass had interbred with the native and possibly endemic) bass species.

What is the current state of the Cuatro Ciénegas reserve now?

Dire. The reserve suffers from numerous problems, including insufficient recognition of the problem and inadequate protection of water resources, among others. Water extraction is grossly beyond sustainability, such that a crisis point has been reached, and very possibly passed, with respect to drawdowns of the aquifer(s) on which the basin’s habitats depend.

You recently reported that the Churince spring is “basically dead,” is there anyway to revive it? Do you think that the other springs and areas of Cuatro Ciénegas will soon dry out and meet the same fate?

I am afraid Churince is lost. At this point, I think focusing on whether Churince can be revived is an understandable but counterproductive pursuit. The question is: How (Can ?) what is left be saved. My fear is that it is a situation of dead springs flowing- only a matter of time before others dry, even if water extraction ceased today. The problem is that effects of water extraction are not immediate. There is a lag-time, and recharge rates (rainwater percolation into the aquifer) are very low. In all likelihood, reduction in the aquifer (from human activity) will take an enormous amount of time to reverse. Given that we appear to be transitioning into a period of aridification (not simply drought) in the entire region, recharge rates are likely to be in decline themselves, which means restoration of the aquifer(s) will take even longer.

Unfortunately, the unique aquatic habitats and fauna of Cuatro Cienegas are in a perilous state, and they cannot wait out aquifer recovery. The upshot is that essentially all aquatic habitats and species associated with them are in serious danger of meeting the same fate as Churince. I am afraid it is only a matter of time, and my guess is loss will come sooner rather than later. I personally doubt, if current trends continue, that in 30, 40, 50 years from now the aquatic habitats and fauna of Cuatro Cienegas will even remotely approach what we see today, should anything of consequence even remain.

If changes are not made soon with water usage policies, how long do you predict the cyanobacteria colonies in particular and the unique aspects of the ecosystem will survive?

I am not sure why you emphasize cyanobacterial communities. It is the entire system that is threatened with collapse. In many habitats, bacteria (broadly speaking) will be the last to go, not the first. As for time frame, the truth is no one knows. As I stated before, I doubt we are talking decades, but anything more specific might be counterproductive. But if you look at the changes that have occurred in Cuatro Cienegas over the last 100 years or so (drop in water table due to water use), especially in the last half century and last decade, you can only be deeply concerned. The progression of habitat loss in the western side of the basin has accelerated, and the direction appears to be towards the headwaters of the Rio Mesquites. If the source of the major river system in the basin is cut off, you can kiss the biodiversity of Cuatro Cienegas goodbye. All evidence suggests time is running out to arrest decline- quickly running out.

Before and after photos of the Cuatro Cienegas ecosystem

All photos below provided by Evan Carson.

Upper System Peripheral Habitat Before

Upper System Peripheral Habitat After

Laguna Grande Before

Laguna Grande After

Laguna Intermedia Before

Laguna Intermedia After

Lower Rio Churince Before

Lower Rio Churince After

Middle Rio Churince Before

Middle Rio Churince After

Upper Rio Churince Before

Upper Rio Churince After

Lower Pool Habitat Before

Lower Pool Habitat After

Close-up of Dead Stromatloites at Laguna Intermedia

Churince System 1960s

To find out more about the Cuatro Cienegas Basin, the unique life that lives there, and current conservation efforts, visit Evan Carson’s website as well as In Cuatro Cienegas Coahuila Water is Everything (in English) and En Cuatro Cienegas El Aqua lo es Todo (in Spanish). Desert Fishes also offers resources on the Cuatro Cienegas ecosystem.