The concept of a desert as an inhabited wasteland is incorrect. Deserts are unique natural habitats with their incredibly diverse flora and fauna and have been home to some the world's oldest civilizations. Besides we should also remember that the desert is easily damaged and is very-very slow to recover. Thus, fragile beauty and unique heritage of world's desert deserve protection.Intense solar radiation, lashing winds and little moisture, i.e., that is less than 25 cm of annual rainfall create some of the harshest living conditions in the biosphere called the 'hot deserts'. In hot deserts, the Sun quickly heats the land by day, producing the highest air temperature in the biosphere. In contrast, the nights are very cold as the temperature goes down tremendously due to loss of heat into the atmosphere through radiation. There is little water and temperature vary widely; one may bake during the day and freeze at night. High temperature during the daytime and persistent winds accelerate water evaporation and transpiration of water in the form of water vapours. High evapo-transpiration and low rainfall characterize all deserts, producing sparse perennial vegetation of widely spaced shrubs.

 

PLANT ADAPTATIONS 

Plants have evolved many adaptations for surviving the rigours of the deserts. There are three life forms of plants that are adapted to deserts: a) ephemeral annuals b) succulents and c) desert shrubs. Ephemeral annuals are also known as 'drought evaders' or 'drought escapers'. They germinate, grow, flower and release seeds within brief period when water is available and temperature is warm. The seeds remain dormant, resisting drought and heat until the following spring. The seeds wait out adverse environmental conditions, sometimes for decades, and will germinate and grow only when the right conditions are available. The succulent plants suffer from dryness in only external environment. There succulent, fleshy stems, leaves and roots serve as water storage organs which accumulate large amounts of water during brief rainy season. Opuntia, Aloe, Euphorbia etc. have mastered the art of enduring in the desert environment by economising in their expenditure of moisture. The desert shrubs or non-succulent perennials suffer from dryness both in their internal as well as external environments. Their morphological and physiological features include rapid elongation and extensive root system, high osmotic pressure and endurance of desiccation, ability to reduce transpiration and reduction in size of leaf blade.

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ANIMAL ADAPTATIONS

Desert animals are much more affected by extremes of temperature than desert plants because the biological processes of animal tissue can function properly only within a relatively narrow temperature range. When this range is exceeded, the animal may die. Thus, most of desert animals rely

on their behavioral, physiological and structural adaptations to avoid desert heat and dryness. The drought-resistant animals and carry out their normal function throughout the year. Their circumvent aridity and heat through morphological and physiological adaptations or by modifying their feeding and activity patterns. they remain in cool and humid underground burrows during the daytime and search for food at night. Mammals as a group are not well adapted to desert life because they excrete urea as an aqueous solution, which involves the loss of much water. Most of the mammals like the kangaroo rat, the pocket mouse and jerboa have adapted nocturnal habitat. They seal their burrows by day to keep their chamber moist, and can live throughout the year without water. They feed on dry seeds and dry plants even when succulent green plants are available. They remain in burrows and conserve water by excreted urine 

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