Deserts of the World

A desert is a region that is characterised by very high or very low temperatures, scanty rainfall and sparse vegetation. Roughly 20% of the earth’s land is covered by deserts. Deserts can be hot deserts with high temperatures or cold deserts with freezing cold temperatures. These deserts present very harsh conditions for human habitation. The people who inhabit these areas adapt to these difficult conditions in order to survive. Due to very little rainfall, the vegetation in desert areas adapts to conserve water as much as possible. The Sahara Desert in Africa, with 9.2 million sq km, is the largest hot desert in the world. Deserts in the world occur naturally, but due to anthropological causes, deserts are expanding or fertile lands are being desertified, which is a growing concern for humanity.

Deserts on Earth have formed over millions of years due to various geological and anthropogenic factors. Geological factors include tectonic movements, ocean currents, wind patterns etc. Anthropogenic factors include environmental degradation by the overuse of natural resources, climate change etc.

The tectonic movements create mountain ranges that can prevent passage of moist air leading to less precipitation on the leeward side. Due to lack of rainfall these regions have the potential to get converted into deserts overtime. The atmospheric circulation of air around 30 degrees north and south of the equator also known as Hadley cells circulation creates dry, high-pressure zones which is why many of the world’s largest deserts are located in this zone. Ocean currents also play an important role in the formation of deserts. The warm ocean currents often lead to hot coastal deserts while the cold ocean currents help in the formation of cold coastal deserts. Geological changes are majorly responsible for the formation of deserts. However, role of anthropogenic factors also plays significant role. Global warming and climate change due to human influence can lead to increased evaporation and reduced precipitation, contributing to desertification which is one of the major issues of present times.

Deserts are those regions of the world which receive very little precipitation, often less than 250 millimeters (10 inches) of rain annually. These regions have extreme temperatures, arid climate and sparse vegetation. Deserts are found on every continent and are mainly of two types - Hot and Cold deserts.

Hot deserts and Cold deserts

Hot deserts : These are the deserts that are characterized by extremely high temperatures and dry climate. Temperature often exceeds 40 degree Celsius in these regions. Vegetation is sparse in these deserts and typically consists of drought-resistant plants like cacti, succulents, and shrubs.

Examples : Sahara desert (Africa), Kalahari Desert (Africa), Mojave Desert (North America), Sonoran Desert (North America) and Arabian Desert (Middle East), Thar desert (India).

Cold deserts : These are the deserts that are characterized by extremely low temperatures . Cold deserts receive minimal precipitation, often in the form of snow rather than rain. Cold deserts are generally located at high elevations.

Examples : Antarctic Desert (Antarctica), Patagonian Desert (South America), Great Basin Desert (North America), Gobi Desert (Asia), Atacama Desert (South America), Ladakh cold desert (India).

• The nature of vegetation in the desert is dictated by the low rainfall and large diurnal temperature range. In hot or cold deserts, the conditions are very unfavourable for the growth of vegetation. Still, there is some form of vegetation found in these deserts, like scrub, grass, roots or bulbs, weeds, etc. But deserts without any vegetation are rare.
• The soil in the hot desert is poor. Due to the high evaporation rate, the salinity of the soil increases. Also, the rate of decomposition is very low because of the low moisture, so humus is not present.
• Due to the prevailing conditions in the deserts, the plants undergo a very specialised adaptation, such as:
  • To deal with a deficiency of water, the roots of plants are long and well spaced, which enables the plant to search for water in the ground.
  • To reduce water loss through transpiration, plant leaves are waxy, hairy, leathery or needle-shaped. In some cases, there are no leaves, and only thorns are present. Some shed their leaves during long droughts.
  • The stems of these plants, such as cacti, store water to deal with long droughts.
  • Seeds also have to adapt to these conditions. They have thick and tough skin and remain dormant until they receive moisture from some rainfall.
• Plants in the hot desert are known as Xerophytic or drought resistant scrubs.
• Polar Vegetation: In polar deserts, the conditions that inhibit plant growth are very low temperatures and low drainage. The ground is frozen for many months; hence the drainage is low. Even in the warmest months, the temperature is low for vegetation growth. Due to the above conditions, the vegetation is primarily mosses, lichens, and sedges.

• Animals in the desert also adapt to the harsh conditions of the desert.
  • Some animals live in underground burrows to avoid water loss and heat. For example, snakes and lizards in the desert remain underground during the day.
  • Many animals have thick skin and are nocturnal by nature.
• Although the desert conditions are not suitable for human habitation, humans have inhabited the deserts around the world by certain site-specific adaptations and lifestyle changes. These inhabitants can be grouped into the following groups:
  • Primitive hunters and gatherers: Some tribes who live in the desert are primitive in their lifestyle and primarily rely on hunting and food collection for their survival. They do not pursue agriculture or herd animals. They collect water by using primitive techniques, for example, collecting the dew early in the morning and carefully storing it in ostrich shells. They prey on animals that are few and far between. They wear clothes, which protect them from heat and retain water. Following are a few important hunters and gathering tribes:
    • Bushmen tribes of the Kalahari desert.
    • Bindibu or Aborigines of Australia
  • Nomadic Herdsmen: They rear animals such as sheep, goats, camels, etc. They rely on these animals for milk, meat, and hides. They wander from places to places for water and green pastures for their animals.
    • Bedouin tribes of the Arabian Desert.
    • Tuareg tribes of the Sahara Desert.
  • Caravan Traders: Before modern transportation, these traders used to travel through the deserts of the Sahara or Russian Turkestan and carry out trade. They primarily used camels for transporting the goods. Now these traders are greatly reduced due to modern transport.
  • Settled Cultivators: They cultivate crops with the help of irrigation systems such as oasis, rivers, dams on the river, and intricate networks of canals. Dams on the Nile and surrounding civilisation are prime examples of this type of settlement.
  • Mining Settlers: Many important minerals are found in the desert, such as gold, copper, silver, diamonds, oil, etc. For mining these minerals, humans settle in these regions, and the whole region is developed for the convenience of settlers. Oil extraction is carried out in the Sahara and Arabian Desert which has transformed these regions.

Deserts are characterised by extreme temperatures, very low precipitation, and sparse vegetation. Life in deserts is difficult for both flora and fauna. Over the years, humans have overcome these harsh conditions and adapted to the climate of deserts. Now there are many minerals that are mined from these deserts and put to use. But this has brought new sets of challenges related to pollution and the displacement of native populations. Also, there are emerging sets of challenges relating to the desertification of fertile lands and the expansion of deserts. The UNCCCD (United Nations Convention to Combat Desertification) has warned of an unprecedented emergency on a global level where a large section of land will become desert. Hence, it calls for the urgent attention of all the member nations to address this massive challenge in a concerted manner.