Considered one of the most inhospitable environments to exist on the Earth’s surface, deserts are surprising due to the struggle of its organisms when faced with adversity. If we have a mental image of a vast territory in which no form of life can develop, we are wrong, because deserts hide a marvelous organic diversity, despite being one of the driest places on earth.
Deserts present precipitations below 250 millimeters a year, and there may even be a shortage of rain for years or decades, conditioning the existing forms of life even further, as well as the strange phenomena that take place when the soil captures the vital resource, as in the case of our country’s florid desert (analyzed further ahead).
Geographically, deserts are found in two separate ranges, between 15° and 35° latitude, in both the northern and southern hemisphere. Its temperatures usually fluctuate hugely between the day and the night due to the fact that the dry air and absence of clouds allow for a strong daily insolation and a drastic loss of heat at night. The maximum temperature usually goes over 40°C, while it can drop to below 0° after the sun goes down.
Deserts of the world
The following standout among the largest deserts of our planet:
– The Sahara Desert: it is the one that has the largest extension on the planet, surpassing 9 million square kilometers. It takes up most of the northern strip of Africa, from the Atlantic Ocean to the Red Sea. It spans the countries of Morocco, Algeria, Tunisia, Libya, Egypt, Sudan, Chad, Niger, Mali and Mauritania, although its boundaries can become diffuse on many occasions, due to the advancing of desert lands and the conflicts among certain countries. The Sahara presents itself as an elevated plain, with an average altitude of almost 400 masl. It is considered the hottest in the world. At noon, the sand is so hot it burns in a matter of seconds.
– The Gobi Desert: an extension of desert that spans from the north of China to the south of Mongolia. Considered a cold desert (it has extreme seasons, like hot summers and winters with temperatures that border 0°C), it takes up close to 1 million 300 thousand square kilometers of surface on the Asian continent. The terrain is continuously struck by winds and it lacks trees almost completely.
– The Kalahari Desert: it spans through the territories belonging to Botswana, Namibia and South Africa, at the south of the African continent. It reaches around 500 thousand square kilometers, presenting fairly arid conditions and sandy soils. Although it presents extreme conditions for most of the year, there is a higher abundance of precipitation.
– The Sonora Desert: it spans part of the southeast of California (U.S.A.) and part of northern Mexico. It is one of the hottest deserts in the world and owes its name to one of the Mexican states it is located in.
– Australian deserts: the Australian surface houses three important desertic formations. They are the Great Sand Desert, the Gibson desert and the Great Victoria desert. The first of them corresponds to an arid region located in northeast Australia, while the Gibson desert constitutes a natural reserve that not only plays host to important dunes, but also salt pans and pastures.Finally, we can say that the Great Victoria Desert is the one located farther south, spanning 750 kilometers from east to west.
Vegetation and aridity
The characteristic vegetation of desert areas has special characteristics in order to withstand great dry periods, with a constant shortness of water. Due to this, many of the typical bushes of this type of biome develop small leaves that are covered by impermeable substances that minimize the loss of the vital element as much as possible. In addition, there are some plants with leaves and stalks of considerable size, which serve as deposits for storing the greatest amount of water possible during the drier seasons. Also, the greenish color helps prevent superficial overheating.
Many of the plant species synchronize their life cycles to the periods of rain and only grow when there is enough humidity. When it rains over the arid surface, seeds germinate, plants develop and some even present eye-catching flowers.
The roots of bushes and cacti also have surprising modifications. They can vary among a few that have a superficial location, which take advantage of the scarce humidity to survive, and others that grow deeply in search of layers of underground waters.
In desert zones in which salinity is quite high, some bushes and cacti have developed salt excretory glands, benefiting their survival.
Fauna and survival
Surviving the extreme conditions of any desert is no easy task. All living beings must condition their organisms and behavior to the extreme temperatures, shortness of water and food, but even so, it is possible to find a great amount of rodents, insects, mammals and birds.
One of the most common behaviors is the nightly activity of the animals that live in the desert, like foxes, coyotes and hares. Many of them bury themselves during the day or remain in burrows to protect themselves from the heat and thus avoid predators. But as soon as the sun begins to set on the horizon, life reactivates surprisingly.
This way, we find species like the Desert Tarantula (Aphonopelma chalcodes), which passes the whole day in its burrow waiting for the sun to go down in order to quickly react before its pray, or the Desert Kangaroo Rat (Dipodomys deserti), which sleeps for the entire day underground in order to cover great distances at night in search of its food.
Staying on your feet for a long time is not possible either because, during the day, the temperature in deserts is quite high, the same as solar radiation. As there are very few areas with shade, some animals have developed a special behavior for walking and not burning their feet. The Collared Lizard (Crotaphytus collaris) refreshes its feet by lifting them off the ground, one or two at a time, while the bird called Roadrunner (Geococcyx californianus) prefers to run quickly over the surface in order to not burn itself.
Man and his impact on the desert
Just like the plant and animal organisms that inhabit it, Man has also made the desert his home. Although these territories are one of the areas with the lowest population density, we can find some peoples that have practiced grazing and agriculture (through assisted irrigation) for centuries.
Currently, desert regions of the Middle East have been invaded by the oil industry, considerably changing the natural landscape and invading the homes of many species. All of the waste produced even pollutes the desert environment and scarce food and water sources that exist in these sectors irreversibly.
In North America, the explosion of urban centers has reached some desert areas, bringing with it not only pollution problems proper of these settlements, but also incorporating irrigation agriculture to sustain the nutrition needs of the population.
This way, foreign species are introduced, the scarce hydro resources available run out and the desert becomes “green”, leaving its main characteristic behind: aridity.
Another of the great problems the areas next to deserts face is the desertification process, meaning, the expansion of deserts towards the periphery of natural deserts, which we will see in depth in later issues.