Ecosystems of Mexico: The Desert

Mexico has a series of exceptional characteristics that make its mosaic of natural communities particularly varied and surprising from every point of view. In a little less than two million square kilometers (1,972,544 km2) you can find almost all the natural landscapes of our planet, from the arid deserts to the humid jungles and swamps.

In addition to this complex geographical panorama, climatic conditions are very diverse: in some places, precipitation is so scarce that it barely reaches 5 centimeters per year, while in others it reaches up to 5 meters. Temperatures are also very variable: some alpine peaks have an intense cold that keeps their snows perpetual, while in the Sonoran desert temperatures can reach 57'C.

Mexico is located in the transition zone between the tropical world of Central America and the Caribbean, and the subtropical and temperate world of North America. Flora and fauna from both origins meet in Mexico, blending in a complex way due to the diversity of altitudes, climates, soil, and rock types. Because of its immense geographic wealth, Mexico is considered one of the richest countries in terms of ecosystem diversity.

Ecosystems of Mexico

The ecosystem is the set formed by living beings, the environment in which they live, and the relationships established among them. These relationships can be both biotic (influences between organisms of the same or different species) and abiotic (physical-chemical factors such as light, temperature, humidity, etc.). Examples of ecosystems are a forest, a desert, etc.

Mexico's main ecosystems are evergreen jungle, deciduous jungle, evergreen forest, deciduous forest, desert, grassland, and mangrove. Getting to know the climate, biological diversity, resource use, deterioration and specific conservation of each of the ecosystems will help us understand and marvel at the biodiversity of Mexico.

The desert definition

Deserts are shrubby plant communities, typical of arid or semi-arid zones, with extreme temperatures. They are characterized by very low rainfall, usually associated with considerable sunshine.

The desert occupies approximately 40% of the country's surface and is, therefore, the largest of all vegetation types in Mexico: It covers most of the territory of the Baja California peninsula, as well as large extensions of the coastal plain and the low mountains of Sonora, covers almost the entire state of Coahuila and Nuevo León, part of Tamaulipas, most of the states of Zacatecas, San Luis Potosí, the northeastern region of Guanajuato, Aguascalientes and a large part of Querétaro, as well as the states of Hidalgo, Puebla and a small portion of Oaxaca. This ecosystem can be made up of different plant and animal species in such a way that, for example, the desert flora and fauna growing in Chihuahua is very different from that found in the deserts of Sonora or Puebla.

Climate

The desert climate is highly variable, ranging from very hot on the coastal plains to relatively cool in the high altiplano. The average annual temperature fluctuates between 12 and 26 degrees Celsius, constantly changing from day to night and from summer to winter. Sunshine is usually intense, humidity is low and, consequently, evaporation reaches very high values.

Average annual precipitation is generally less than 500 mm, in large extensions, it is between 100 and 400 mm per year and in the extreme northwest of Sonora as well as in large areas of Baja California, it is less than 100 mm. The aridest part of Mexico corresponds to a strip located along the boreal zone of the Gulf of California, where it rains less than 50 mm on average per year.

Rainfall, besides being scarce, is usually irregular, the number of dry months varies from 7 to 12 per year, but it is not uncommon for up to 18 months to pass without apparent rainfall. In the driest areas, there can be several years without significant rainfall.

The causes that originate the existence of desert zones are the presence of dry air in the upper part of the troposphere; the extensive downward movements of air and its warming, even in areas close to the sea; the lack of vertically developing clouds, which are the only ones that can cause precipitation; and the orographic shadow caused by mountain barriers that hinder the passage of humidity from the sea, especially in areas where winds blow persistently from the sea to the land. All these factors are present in Mexico and are the cause of the high percentage of arid zones.

Biodiversity

The floristic composition of the deserts is very varied. The Compositae family is very well represented, sometimes making up about a quarter of the flora. Legumes and grasses are also quantitatively important, the former mainly in hot climates, while the latter are generally more abundant in cooler climates. It can be estimated that the Mexican xerophytic flora is autochthonous since it has little resemblance with the flora of the arid zones of the United States, however, it presents certain similarities with the flora of some regions of South America.

About the fauna, the biological diversity in arid zones is very varied and inconstant in composition, varying according to the zone, the season, and the rainfall regime, however, each animal group has xerophilic representatives of the group of protozoa (unicellular animals), which are essentially aquatic, there are in the desert those that can encystify during the dry season, and then become active in the rainy season, feeding among the grains of wet sand. The cyst can remain dormant for years.

In oases and irrigated areas, annelid worms have some representatives. Mollusks (like some snails) form the visible element of the fauna of some desert regions, their activity is confined to the winter months and their mating occurs during the rains, in some parts of California deserts the ground may be bleached by their shells.

The group of arthropods such as ants, termites, spiders, scorpions, butterflies, moths, bumblebees, crickets, grasshoppers, locusts, flies, beetles, and solifuges is widely represented in desert areas. All of them present life cycles adapted to drought conditions -the time when the larval stages of development occur- and the rainy season with the presence of adults. Amphibians are not abundant in hot, dry climates due to the nature of their skin, however, frogs and toads are found in temporary pools, buried or on rocks next to watercourses.

Among the reptiles, snakes and lizards are a striking and important element of the desert fauna. The latter are found in great numbers and are adapted to tolerate the heat, even above 40'C. Desert tortoises are rare and protect themselves from the heat by digging deep burrows beneath the surface. Among the birds, the most common are vultures, eagles, owls, and hawks; roadrunners are also very common.

Within the diversity of arid zone mammals, the best represented and most numerous group is that of rodents; examples include the kangaroo rat and squirrels. Another important group is that of carnivores; among them are hyenas, foxes, coyotes, felines, skunks, and ferrets. Among the lagomorphs, the best represented are the hebes. Bats are also found in this area and most cases they feed on insects.

Farming and livestock farming in the desert

Agriculture without the aid of irrigation is often practiced in less arid zones. Cotton, wheat, and soybeans are the most characteristic crops grown on irrigated land, while corn, barley, and sorghum are preferred for rainfed land. In some regions of Hidalgo, Tlaxcala and the State of Mexico there are plantations of maguey pulquero (Agave atrovirens and A. salmiana). The cultivation of prickly pear cactus (Opuntia sp ) is gaining more and more followers in some areas of the center of the country.

Although desert lands are arid and offer little food for livestock, livestock raising is often an optional activity. Goats usually predominate because of their better adaptation to the drought conditions and the use of the prevailing shrub vegetation, but in some areas, cattle, sheep and even horses are more abundant.

Mexico has a large number of forage, medicinal, and food plants that over thousands of years have adapted incredibly well to the climates of arid zones. The plants from which man obtains some non-timber benefits are, among others, forage grasses and potential species such as:

the crazy squash (Cucurbita foetidissima), which is mainly used as fodder for goats and cows,

guayule (Parthenium argentatum), a plant that produces large quantities of rubber,

candelilla, which is of enormous industrial importance in the states of Coahuila, Chihuahua, Zacatecas, Nuevo Leon, and Durango, is distributed over an area of approximately 350,000 km2; wax production is estimated at 3,000 million kilograms with close to 21,000 families benefited,

lettuce and palms (Yucca spp ), which are widely used by farmers as a source of ixtle fibers; unfortunately, these have to compete with the synthetic fiber market, so it is necessary to improve their quality to facilitate submerging in the market,

Nopal cactus (Opuntia spp.) is one of the most abundant plants in Mexico and for the inhabitants of desert areas it is an excellent option as food for its fruits or tender shoots, as well as for livestock feed, especially when forage is scarce,

agaves have had different uses since ancient times; in Mexico, they are mainly used for the production of fibers. The most cultivated species are Agave fourcroydes -commonly known as henequen- and Agave sisalana, although there are other species from which honey and fibers are obtained or used as living barriers for erosion control.

Other species also cultivated are Agave angustifolia, a small plant with a compact rosette and numerous pale green leaves and notable leaf production, and Agave amaniensis. Or blue sisal with long, heavy leaves that lack thorns and contain a large amount of fine fiber.

Deterioration in the desert and other causes

The main mechanism of degradation in the desert is overgrazing by all species: cattle, sheep, goats, etc. Its most notable effect on the xerophytic vegetation is the gradual substitution of plants palatable to livestock for others that they do not touch, an effect that is accentuated by intense and irrational use.

Another cause of the deterioration of the vegetation has been the illegal trade of cacti, which has been practiced for a long time. It is estimated that some 30 tons of these plants leave Mexico each month, and despite the existence of a law prohibiting this trade, it has not been respected, which is why many of the cacti are in danger of extinction. The deterioration of the habitat is a determining factor in the disappearance of numerous plant species, an example is the cactus Artocarpus kotshou beyanus, which is considered an endangered species due to the deterioration of its habitat.

An example of conservation

A few decades ago, ranchers in the states of Nuevo León, Coahuila, and Tamaulipas began the task of carrying out a conservation plan for the white-tailed deer, Odoco: leus virginanus texanus, which was in danger of extinction, implementing a total 5-year ban on all wild species found on their ranches.

At the end of this period, the populations of wild animals such as the collared wild boar (Drcotylestajacu), the black-tailed hare (Lepus californicus), the eastern rabbit (Sylinlagus floridanus), birds in all their varieties such as the quail (Lophortyx), the pigeon (Zenaida), pheasants of the genus Phasianus, the wild turkey (Meleagris gallopavo), some aquatic birds, mammals such as the puma (Felisconcolor), the wildcat (Lyns rufus), the coyote (Canis latrans) and the gray fox (Urocyon cmnereoargenteus), repopulated hundreds of hectares of these ranches.

In this way, the ranchers proved that it was possible to make rational use of natural resources. Other ranchers joined this plan to form what is now known as the National Association of Diversified Ranchers, which legalized the regular use of wildlife.

By Citlalli Álvarez Saulés, Source: Correo del Maestro