EV; Project: Culberson

The Chihuahua Desert
The Trans-Pecos Sub-Ecoregion
Ecological Sustainability Plans
Self-Sufficiency Plans

(image credit: unknown)

The Chihuahua Desert

Of the four great North American Deserts, the Chihuahua Desert is the largest, and the easternmost and southernmost. In terms of numbers of species and endemism, it is one of the three most biodiverse desert ecoregions in the world.

The Chihuahua Desert lies in the intermountain basin areas between the Rocky Mountains, the Sierra Madre Oriental, and the Sierra Madre Occidental; and compared to most other deserts is primarily composed of high elevations, typically between 2,000 to 6,000 feet. Most of the Chihuahua Desert is in Mexico. The northern portion of the Chihuahua Desert extends into Texas mostly west of the Pecos River, into southern and central New Mexico, and into a small portion of southeastern Arizona.

The Chihuahua Desert is largely a basin and range desert which means it mainly consists of basins interrupted by many small mountain ranges. Some of these ranges are called sky islands, and due to their high elevations, have cooler and wetter climates that host coniferous and deciduous woodlands. The Chihuahua Desert is also largely a rainshadow desert, which means that as the wind blows, it is on the leeward side of Mexico’s two great mountain ranges, the Sierra Madre Oriental and the Sierra Madre Occidental. As the wind blows clouds up the windward sides of the mountains, the air cools and condenses, and rain falls. When the clouds reach the Chihuahua Desert, the warm air causes them to expand and dissipate. When it does rain, rainfall averages between 8 to 12 inches and occurs primarily during the late summer months (late June or early July to September) via the Mexican Monsoon.

There are many opinions concerning what the word ‘desert’ means. Ecoculture Village loosely defines the word ‘desert’ as a natural arid habitat that characteristically keeps little moisture; generally this means that it receives less than approximately 10 inches of precipitation per year and may also have a higher rate of evapotranspiration [water loss through both atmospheric evaporation and plant transpiration] than precipitation. Semiarid grasslands are also known as steppes and they typically receive between approximately 10 to 20 inches of rainfall per year and do not have a higher rate of transpiration than precipitation. Much of what is today called the Chihuahua Desert is actually wastified (commonly called “desertified” ¹) steppe that, because of mankind’s negative effects on the native flora and soils, now has a higher rate of evapotranspiration than precipitation.

¹ Deserts are naturally occurring ecosystems and in Ecoculture Village terms, ‘desertification’ is a natural geologic process in which a non-desert habitat evolves into a desert habitat. As such, I have given the name ‘wastification’ in reference to the broad category that is human induced habitat destruction. Others commonly call this unnatural and careless human occurrence “desertification”, even though these wastified areas in no way resemble healthy desert habitats. Wastification can be thought of as the disease that natural landscapes suffer from when mankind’s activities and processes are not harmonious with the activities and processes of the natural landscape. Wastification causes loss of soil fertility (soil’s ability to support plant communities). Loss of plant cover (e.g. from livestock overgrazing and agricultural expansion), soil compaction (e.g. from industry; cattle), and subsequent topsoil loss (e.g. from wind and rain runoff) all lead to loss of soil fertility, which in turn leads, not only to the loss of the intrinsic value of the ecosystem, but also to the loss of the human communal potential once inherent to the land.

It is important to understand that ecoregions traditionally outside of the Chihuahua Desert ecoregion have been significantly degraded by negative human activities, mostly overgrazing and irrational water use and agriculture. Thus, semiarid areas (mostly grasslands and shrub-grasslands) that were once not considered desert are included in the Chihuahua Desert ecoregion. As a result, the Chihuahua Desert is thought to have grown by approximately one-third of its original natural size, and these sub-ecoregions now thought of as a part of the Chihuahua Desert are now mostly dominated by desert shrubs which have displaced the native plants mostly due to overgrazing of once abundant native grasses.

Larrea tridentata (Creosotebush) is nearly cosmopolitan to the Chihuahua Desert ecoregion and solely occupies many vast stretches. Other common widespread plants are Acacia spp. (Acacias), Prosopis spp. (Mesquites),and Yucca spp. (Yuccas). Flourensia cernua (Tarbush) is a more scattered indicator species which forms extensive stands where soil and moisture conditions are more favorable to them. Other plants characteristic of the Chihuahua Desert are Agave spp. (Agaves) such as Agave lechuguilla (Lechuguilla); Atriplex canescens (Fourwing Saltbush), Bouteloua eriopoda (Black Grama Grass), Condalia warnockii(Warnock’s Javelina Bush), Dasylirion spp. (Sotols), Ferocactus wislizenii (Barrel Cactus), Fouquieria splendens (Ocotillo), Hilaria mutica (Tobosa Grass), Koeberlinia spinosa (Allthorn), Mimosa spp. (Mimosas), Nolina spp. (Nolinas), and Opuntia spp. (Opuntias).

Some plants common to the northern Chihuahua Desert include Agaves (including Agave lechuguilla); shrubs such as Atriplex canescens (Four-winged Saltbush), Parthenium incanum (Mariola), and Prosopis glandulosa (Honey Mesquite); a variety of small to medium-sized cacti; and yuccas (Yucca elata and Yucca torreyi). Various associations of plants growing together in different areas are determined by many different factors, such as altitude, moisture, slope angle, and soil type. In the northernmost reaches of the Chihuahua Desert, Larrea tridentata (Creosotebush) is found growing dominantly along with Acacia neovernicosa (Viscid Acacia) and Florensia cernua (Tarbush).

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The Trans-Pecos Sub-Ecoregion

Paleoecological evidence suggests that long ago (as recently as ~10,000 years ago) much of the Trans-Pecos sub-ecoregion was mesic (moderately moist) coniferous woodland dominated by Juniperus spp. (Junipers) and Pinus spp. (Pines, notably Piñons and others). Because of geologic processes (including increased aridity) by the time Europeans settled in America, the Trans-Pecos had naturally evolved into grasslands. Since then, the landscape has been altered dramatically by mankind. So much so that the region has changed in terms of plant and animal life more during the last 150 years than ever before in mankind’s history. Primarily, these relatively recent changes are the result of livestock overgrazing, wildfire suppression, and frequent drought; and they continue today. Although drought is a factor, it could and should be locally compensated for by way of water use legislation, as it is the one factor that there seems to be no control over other than that part of it that may be the result of the manmade portion of global warming. Other significant causes of habitat decline (biodiversity loss) in the region are the spread of urbanization, agriculture, and irrational use of water; and the illegal collection of species, many of which are species of concern, whether endangered, threatened, or rare.

Ecoculture Village has acquired an 11.404 acre site just east of Van Horn, in Culberson County, which is the second county due east of El Paso County, in west Texas. The site is rented from me (Troy Boylan) at the cost of its annual property taxes. The site (see Image #1) is in the Rio Grande Basin Subsection (north of El Rio Grande) of the Northern Chihuahua Desert. For simplicity’s sake, I have named the site Ecoculture Village; Project: Culberson. It is located in an almost completely wastified site with little to zero topsoil and almost zero plant cover.

A landscape with no topsoil is a worst case scenario. Without topsoil, water is not conserved. Instead, rainwater hits the bare ground causing it to harden over into a crust as the smaller particles get compacted between the larger ones. As a consequence, seed germination becomes more difficult, and water runoff increases. Subsequently, water does not infiltrate into the soil as it once did when runoff was halted by grasses and other plants, and thus it does not percolate deeply as it once did; and it is not stored in plant roots as it once was.

The loss of the Trans-Pecos grasslands has decreased the ability of the land to store water, contributing to the fact that many of the springs, their cienegas (desert marshes) and creeks, and the plant and animal communities associated with them, that were once prevalent in the region have vanished. These riparian habitats teemed with life and many contained numerous rare plants, but most are now dry. The drying up of springs is also due to the large of number of wells that were dug in the region, which have drastically lowered the water table, and which have also pumped dissolved salts from the depths of the aquifers to the surface. Of the few springs that remain, only three are permanently conserved.

Previously, the Ecoculture Village; Project: Culberson site was part of the surrounding desert scrub bioregion that is present today. Even more previously, the site was a part of the desert grassland which was lightly interspersed with woody and succulent species.

The deep-rooted perennial, warm-season bunchgrasses (possibly including Andropogon spp. [Bluestems], Bouteloua curtipendula [Sideoats Grama], Bouteloua gracilis [Blue Grama], Digitaria californica [Arizona Cottontop], Heteropogon contortus [Tanglehead], Leptochloa dubia [Green Sprangletop], and Pleuraphis mutica [Tobosagrass]) that were the dominant species of the previous desert grassland are fire-tolerant, as they have growing points that remain protected underneath the soil. They are also assisted by or even dependent on periodic fires, as fire stimulates their seeds to germinate. On the other hand, fire kills off any woody species that have not grown high enough in between fires to escape the burning grasses. Many of the native grasses are historically reported to have been belly high to a horse; and so high only the heads of antelope could be seen above them.

Overgrazing numbers of livestock were introduced into the lush region, which selectively prefer the leafy perennial grasses over short-rooted annual grasses (including Aristida pp. [Threeawn], Bouteloua trifida [Red Grama], Scleropogon brevifolius [Burrograss], Tridens muticus [Slim Tridens]), and other Tridens spp. [Fluffgrass]. In the absence of the selective pressure that is the overgrazing of livestock, the grasses are allowed to fully photosynthesize, which is required for healthy root development, which is in turn necessary for resistance to drought. Also because of overgrazing, the deep-rooted fire-resistant bunchgrasses were unable to reach reproductive age and drop seeds, and they lost their dominance. Without the vast tracts of grasses, the area of wildfires declined, and desert woody species and short-rooted non-fire-tolerant annual grasses began to thrive in their place. But even so, the deep and spreading roots of the woody species decrease available water in the soil making it harder for even the most drought-tolerant of the short-rooted grasses to survive. Also, as mankind’s presence in the area continued to grow, subsequent fire suppression in what areas still had grasses allowed the woody plants to gain a dominant foothold across the region.

The subsequent desert grassy scrubland continued to be overgrazed but because woody species naturally displace grasses in the absence of fire, whether grazed or not, in many areas there are now no grasses at all. Dominant numbers of Acacia constricta (Whitethorn Acacia), cacti, Flourensia cernua (Blackbrush, Tarbush), Larrea tridentata (Creosotebush), and Prosopis glandulosa (Honey Mesquite) are characteristic of now wastified once thriving desert grassland areas in the lower elevations; and dominant numbers of Cylindropuntia spinosior (= Opuntia spinosior) [Cane Cholla], Gutierrezia sarothrae (Broom Snakeweed, Perennial Broomweed), Mimosa aculeaticarpa var. biuncifera (Catclaw Mimosa), Nolina texana (Sacahuiste), and Opuntia spp. (Prickly Pear) are characteristic of now wastified once thriving desert grassland areas in the higher elevations. As stated previously, it is estimated that the desert scrub habitat characteristic of most of the Chihuahua Desert has expanded by approximately one-third its size due to wastification.

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Ecological Sustainability Plans

Ecoculture Village; Project: Culberson, initially, plans to demonstrate how the wastification of a desert habitat can be reversed by applying rational land management principles. This process will include water conservation, soil fertility improvement, and indigenous habitat establishment and enhancement tactics; such as contour swaling, mulching, and other phytostabilization techniques.

Soil hydrology (water infiltration, retention, and deep percolation) and greater wildlife numbers and diversity are superiorly maintained by deep-rooted bunchgrasses, although shallow-rooted species are better than bare soil. Because of this fact, many desert grassland conservation projects in the Trans-Pecos ecoregion include prescribed burning to eliminate woody plant encroachment. Because of the small size of the Ecoculture Village; Project: Culberson site, and because of the need for onsite produced mulch material, Ecoculture Village will keep its woody plant population managed by way of cutting and not by prescribed burning. This will provide some of the much needed mulch required to rebuild the soil to fertility.

Ecoculture Village seeks to reverse the wastification of the Ecoculture Village; Project: Culberson site with wildlife habitat in mind, to the effect that:

(1) a desert scrubland is reestablished in some areas; and
(2) a small-scale (actually an edge-habitat or a viable balance between the two previous habitats) desert grassland interspersed with woody and succulent species, is reestablished in other areas.

The main problem with reestablishing the original grassland bioregion at the Ecoculture Village; Project: Culberson site other than the site size limitations which restrict prescribed burning; is limited or lack of knowledge/availability of original native grass species. These can be researched and speculations can be made, but it might also be that some or all of the original species in any given area are extinct.

In addition to keeping scrub growth in check physically, the success of the latter habitat will rely on introducing into the site, deep-rooted perennial, as well as annual grasses indigenous to the greater bioregion. Some of these grasses might be able to benefit from some sparse shrub cover, which should prove to be enhancing to the habitat with its edge effect. Perhaps we will find that certain species of grasses and certain species of shrub or tree function as companion plants, a potentially or actually evolved relationship previously kept from observation by wastification.

Thus, a main feature of Ecoculture Village; Project: Culberson will be wildlife habitat buffer zones. These zones will be implemented and managed in order to reestablish, conserve, and improve wildlife habitat to the effect of maximum biodiversity, and Ecoculture Village will continue to consult and perhaps work with the Texas Parks and Wildlife Department (TPWD) Private Lands and Habitat Program to this end. I am planning to coordinate Ecoculture Village’s wildlife conservation efforts with the assistance of the TPWD Landowner Incentive Program and the following 2008 Farm Bill Programs and any other relevant programs to the fullest extent possible: Conservation Stewardship Program and the Wildlife Habitat Incentive Program.

The following is a partial list of species of concern, which have a potential or known presence in the habitat indigenous, prior to its wastification, to the Ecoculture Village; Project: Culberson site, and which Ecoculture Village seeks to be able to provide for with, and if possible to introduce into, wildlife habitat buffer zones:

• Agave glomeruliflora (Chisos Agave); rare
This species grows in gravelly or rocky soils in oak-juniper woodlands and mesquite-creosote bush-invaded grasslands at elevations of about 600-1800 m (1950-5900 ft); flowering mid-spring to early fall.

• Lycium texanum (Texas Wolf-berry); rare
This species grows in semi-desert grasslands and thorn shrublands on sandy, gravelly, and/or loamy soils, on very gently sloping terrain as well as in rocky areas in canyons, often over limestone at moderate elevations; flowering March-October.

• Nolina arenicola (Sand Sacahuista); rare
This species grows on windblown quaternary sand in dune areas east of Van Horn; also in shrublands on steep Permian limestone slopes in the Guadalupe Mountains; flowering March-August.

• Phrynosoma cornutum (Texas Horned Lizard); threatened (state status)
This species is the largest horned lizard in Texas. It lives in open, arid and semi-arid regions with sparse vegetation, including grass, cactus, scattered brush or scrubby trees; soil may vary in texture from sandy to rocky; burrows into soil, enters rodent burrows, or hides under rock when inactive; breeds March-September. Much of its decline is the result of wastification, in the form of plowing. The lizards hibernate and lay their eggs underground during the winter and summer, and tilling the earth disturbs that process. Chemicals such as pesticides and defoliants are also directly and indirectly suspect. Other factors include pet collection, road kill, and urbanization. In recent years, their decline is perhaps also due to the spreading of the introduced Solenopsis invicta (Red Fire Ant), which has arguably contributed to the decline of many animal species over the last two decades. The logic is that the fire ants feed on Pogonomyrmex barbatus (Harvester Ants [which feed mainly on seeds but also on dead insects]), which, along with grasshoppers and beetles, are a main food source for the lizards. Fire ants might also feed directly on the lizards and their eggs.

• Sphingicampa raspa (A Royal Moth); rare
The preferred host food plant for Sphingicampa raspa (A Royal Moth) caterpillar is Acacia angustissima (Prairie Acacia). A good density of these will be planted in the wildlife conservation buffer zone(s) to provide food, shelter, and reproductive cover for Sphingicampa raspa and other species. Acacia angustissima is a pioneering leguminous nitrogen-fixing tree species with protein-rich seeds edible to both wildlife and humans.

A major portion of the Ecoculture Village; Project: Culberson site, which qualifies as agricultural land, will be used for wildlife habitat management. Ecoculture Village will be engaged in specific wildlife habitat management activities.

Grazing Management:

Grazing livestock and other attempts at non-through-gate access to the Ecoculture Village; Project: Culberson site will be denied by a thick border of impassable ‘living fences’ or hedges of thorny species such as Agave lechuguilla (Little Lettuce Agave), Fouquieria splendens (Ocotillo), Opuntia ficus-indica (Indian Fig Opuntia), and Yucca (Yucca). These species are of value to wildlife as food, shelter, and reproductive cover; and to humans as food, medicine, and utility. The absence of grazing livestock will allow the grasses to grow unimpeded so they can photosynthesize properly, which is required for healthy root development, which is necessary for resistance to drought, enabling them to reach reproductive age and drop seeds.

Wildlife Restoration:

In restoring wildlife to the site, and because of the small size of the site, consequently to adjacent areas as well; Ecoculture Village will be:

1) restoring and improving habitat to good condition for several targeted species and
2) reintroducing and managing several TPWD-approved native species’ within the habitat’s carrying capacity as part of a TPWD-approved restoration area.

Supplemental Water:

… by way of swales, possibly ponds, rainwater catchment, and runoff diversion.

Supplemental Shelter:

… for wildlife by way of brush piles, establishing woody plants, living fence management, and nest/bat boxes (if applicable), etc.

Census and Monitoring of Endangered, Threatened, or Protected, and Non-game Wildlife Species:

Through periodic counts, management will be improved and knowledge of the local, regional, or state status of the species’ will be increased. These practices will include developing checklists of wildlife diversity on the site and adjacent and other nearby areas and will be a part of a comprehensive wildlife management plan.

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Self Sufficiency Plans

Swales will be dug on contour throughout the site. The mounds up-slope and down-slope of the swales will be heavily mulched, and nitrogen-fixing tree species will be planted along with native food, medicine, and utility tree, shrub, cactus, and herb species.

A ‘food forest’, fenced in, would feature trees and shrubs that are not necessarily indigenous to the area, but that are compatible with the climate and soil conditions. The area would be heavily mulched, and would provide a variety of edible fruits, and also serve as forage habitat for chickens, which would in turn fertilize and ‘encourage’ the soil. Within the confines of the food forest fence would be a chicken house. Optionally, rather than fencing surrounding the food forest, one or more mobile chicken pens would serve to keep the chickens confined to the food forest.

Appropriate technologies featured will include a large (1000+ sq. ft.) rain-water catchment structure with cisterns; moldering toilets; solar cookers; solar heated showers; and solar water distillers. Eventually, photovoltaic and wind turbine technology may be implemented.

Ecoculture Village; Project: Culberson will ultimately grow to be an excellent example of how many of the possibilities inherent to an integrative, yield-intensive, rural site in an arid/semi-arid climate can be attained. Visitors will be welcome, and a visitor center providing material information about the project and the surrounding region is also an option.

Table #1: Van Horn, TX; Monthly Average Precipitation in Inches, High and Low Fahrenheit Temperatures, and Record High and Low Fahrenheit Temperatures (year).

Table #1, continued: Van Horn, TX; Monthly Average Precipitation in Inches, High and Low Fahrenheit Temperatures, and Record High and Low Fahrenheit Temperatures (year).

References:

Hastings, James Rodney; Vegetation Change and Arroyo Cutting in Southeastern Arizona; Journal of the Arizona Academy of Science, Vol. 1, No. 2 (Oct., 1959); pages 60-67; Arizona-Nevada Academy of Science.

Richardson, Calvin; Trans-Pecos Vegetation: A Historical Perspective, Trans-Pecos Wildlife Management Series Leaflet No. 7; June 2003Texas Parks and Wildlife.

Van Devender, T. R.; Desert Grassland History; M. P. McClaran and T. R. Van Devender, Eds.; The Desert Grassland; 1995; pages 68-99; Univ. of Arizona Press, Tucson.

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