Desert Essay ⋆ Environment Essay Examples ⋆ EssayEmpire

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De se rts cover a bou t 35 percent of the earth’s surface and are mainly located between the latitudes of 5-35 degrees north of the equator. They are regions characterized by high aridity, little vegetation cover and large surfaces of bare soil, and highly adaptable plants and animals that can survive long droughts. According to bioecological definitions, the world’s deserts represent all ecoregions of the world that harbor desert vegetation, identified by xerophilous life forms and the general desert-adapted physiognomy of the dominant plants.

Among these, aridity is the most prominent indicator, commonly measured by the Aridity Index, an estimator for the ratio between mean annual precipitation and mean annual potential evapotranspiration, which is less than 1.57 inches (-40 millimeters) for arid deserts and -.79 inches (-20 millimeters) for semideserts. Aridity is highest in the Saharan and Chilean-Peruvian deserts, followed by the Arabian, East African, Gobi, Australian, and South African deserts, and lower in the Thar and North American deserts. Desert climate can be hot or cold. Among the hot deserts, there are two that have two rainy seasons-Somora and Karoo. Three have one rainy season: Northern Sahara, Mohave, Middle-Asian. Deserts with summer rains include southern Sahara, inner Namib, and Atacama. Central Australia is a desert characterized with few rains during any season. Coastal deserts that have fog but no rain include the North Chilean Coastal desert and outer Namib. Finally, deserts without any rain or vegetation include the Central Sahara.

Precipitation

Desert climate is characterized by precipitation of less than 9.84 inches (250 millimeters) with high variability, high diurnal variations of temperature, and strong solar radiation. The high aridity as well as typical pulse-type variations in desert environments are caused by global atmospheric and oceanic phenomena, such as the position of the jet streams, the movement of polar-front boundaries, the intensity of the summer monsoon, El Nino southern Oscillation events, and even longer-term ocean cycles, such as the Pacific Decadal Oscillation. Driven by these large-scale forces, the intensity of midlatitude continentality, ocean upwellings, and rain shadows-the major factors modulating the distribution of arid lands-the intensity and frequency of rain pulses on a local scale may vary substantially with time, and in a seemingly unpredictable fashion. This structures desert ecosystems in a way that requires a physical and behavioral adaptation to the patch dynamics of primary production, water, and nutrient cycling in scales of space and time. During pulses of bounty, the fragile seedlings of desert plants can germinate, establish, and prepare for long droughts by burying their roots deep in the desert soils. To a large extent, it is the heterogeneity of pulses that drives the high biodiversity of desert ecosystems.

Typical desert soils are aridisols, characterized by little weathering of the maternal rocks and low organic matter in the surface layer, formed under the typical influences of desert conditions by strong winds, scattered but torrential rains, and high temperatures. The materials in these soils are often cemented together, forming water-impervious hard-pans, sometimes containing salts or gypsum. The low soil cover exposes deserts to much more wind and water erosion than any other environment as a result of steep slopes.

Humans living in deserts undergo considerable dehydration, and therefore have learned to cope with the dry environment for their survival with a panoply of behavioral, cultural and technological adaptations. Traditionally, desert livelihoods were made of three types-hunter-gatherers, pastoralists, and farmers. To adapt to the patchiness of the desert ecosystems, for instance, the movements of pastoralists mimic the variability and unpredictability of the landscape, and range reserves provide saving banks and buffers against periods of scarcity in food, water, and money. Desert agriculture occurs mostly around oases and desert rivers, which often provide silt and nutrients through flooding cycles. These ways of life, however, are changing rapidly, from hunter-gatherers to cattle ranchers, and from nomadism and transhumance to tourist-targeted activities. In recent times, extraction of minerals, use of vast spaces for military facilities, energy-intensive urban developments, and tourism have increasingly changed the ways of life for some desert populations.

However, due to the extremely slow rate of biological activity in deserts, these ecosystems take decades, if not centuries, to recover from even slight damage. Moreover, because traditional livelihoods in deserts require large areas, they are particularly vulnerable to political and environmental changes. Irreversible damages have been caused in previously good agricultural grounds in deserts by large-scale modern developments, such as dam constructions for water and energy supplies. Finally, the specific aesthetic features and atmospheres of deserts, their silence, wideness, beauty, bareness and emptiness, have always created an intimate spiritual relationship between humans and the desert landscape. All three monotheistic religions have roots in desert regions, where they still remain places of spiritual inspiration and meditation.

Bibliography:

W. Breckle, Sustainable Land Use in Deserts (Berlin Springer, 2001) D. Jasper, The Sacred Desert: Religion, Literature, Art, and Culture (Oxford, 2004);
Monem Balba, Management of Problem Soils in Arid Ecosystems (CRC Press, 1995);
Maryam Niamir-Fuller, , Managing Mobility in African Rangelands: The Legitimization of Transhumance (Intermediate Technology Publications Ltd., 1999);
J. Skuijns, Semiarid Lands and Deserts: Soil Resource and Reclamation (Marcel Dekker, 1991);
Walter Whitford, Ecology of Desert Systems (Elsevier, 2002).