Recent Biology Articles Ecology
Recent Biology Articles Ecology
Introduction to Deserts
In this brief introduction we will discuss the geographical location of deserts, some of their main physical characteristics, flora and fauna impact on climate and human use.
Main locations and types of deserts
A desert is a landscape or region receives a very small amount of rainfall less than enough to support the growth of plants. Deserts are defined as areas with an average annual rainfall less than 250 mm (10 in) per year, or as areas where more water is lost through evapotranspiration than falls as precipitation. Deserts are part of a broad classification regions that at an average annual basis, have a moisture deficit (ie they can potentially lose more than is received). Deserts are located where vegetation cover is sparse to almost nonexistent, and make up about one-third (33%) of the Earth's surface. This brief introduction focusing on hot deserts. Hot deserts have usually a large diurnal and seasonal temperature range with high daytime temperatures and low night temperatures (because of extremely low humidity). In hot deserts temperature in daytime may reach 45 ° C/113 ° F or higher in summer and dip to 0 ° C/32 ° F or lower during the winter. Dry desert air is unable to block sunlight during the day or trapping heat at night.
Thus during daylight most of the sun's heat reaching the earth, and once the sun goes down over the desert cools quickly by radiating its heat into space. Urban areas in deserts lack large (more than 14 ° C/25 ° F) daily temperature variations, partial caused by the urban heat island effect. Many deserts are formed by rain shadows, mountains blocking the way of precipitation to the desert (the lee side of the mountain). Deserts are often composed of sand and rock surfaces. Sand dunes called ergs and stony surfaces called Hamada. Exposures of rocky terrain are typical, and reflect minimal soil development and thin vegetation. The soil is rocky because of the low chemical weathering. The largest hot desert is the Sahara in northern Africa, covering 9,000,000 square kilometers and 12 countries. Other big hot deserts include Arabian Desert, Kalahari Desert, Great Victoria Desert, Great Basin Desert and the Syrian desert. Deserts are also classified by their geographical location and dominant weather pattern as trade wind, mid-width, rain shadow, coastal, monsoon, or polar deserts. Former desert areas presently in non-arid environments is paleodeserts eg Nebraska Sand Hills. Montane deserts are arid places with a very high altitude, the most prominent example is found north of the Himalayas, especially in Ladakh region Jammu and Kashmir, in parts of the Kunlun Mountains and the Tibetan Plateau.
Many places in this category have elevations exceeding 3,000 meters (10,000 ft) and the thermal regime can hemiboreal. These places owe their profound drought (the average annual rainfall is often less than 40 mm or 1.5 in) to be very far from the nearest accessible sources of moisture. Montane deserts are normally cold. Rain shadow deserts are formed when high mountain ranges block clouds from reaching areas in the direction the wind is going. When the air moves over the mountains, it cools and moisture condenses, as rainfall on the wind side. When the air when the lee side is dry, because it has lost most of its moisture, resulting in a desert. The air then warms, expands, and blows across the desert. The warm, dry air takes the remaining moisture in the desert. An example of a rain shadow desert, Death Valley, located in the rain shadow of the Pacific Coast Ranges of California and the Sierra Nevada Mountains.
Main Physical Properties
Sand covers only about 20 percent of Earth's deserts. Most of the sand in sand sheets and sand seas-large regions of undulating dunes. In general, there are six forms of deserts: 1) Mountain and basin deserts 2) Hamada deserts, which consist of plateau landforms 3) Reg consisting of rock pavements 4) ergs, which is formed by sand seas 5) Intermontane Basins and 6) Badlands which are located on the edge of dry land include clay-rich Earth Nearly all desert surfaces plains where Eolian deflation-removal of fine-grained material by the wind-has exposed loose gravel consisting predominantly of pebbles but with occasional setts. The remaining surfaces of arid soil is composed of exposed bedrock outcrop, desert soils and flood deposits, including alluvial fans, Playas, desert lakes and oases. The rock outcrop occur as small mountains surrounded by extensive erosion plains. Several different types of dunes exist. Bark Ancestors produced by strong winds blowing across a flat surface and are crescent shaped. Longitudinal or Seif dunes are dunes that are parallel with a strong wind that blows in one general direction. Transverse dunes run at a right angle to the constant wind direction. Star dunes are star-shaped and have edges that spread out around a point. Oases are vegetated areas moistened by springs, wells or irrigation. Many are artificial. Oases are often the only places in deserts that support crops and permanent habitation.
Flora and Fauna
Deserts have a reputation for supporting very little life, but in reality deserts often have high biodiversity, including animals that remain hidden during daylight hours for to control body temperature or to limit moisture needs. Some animals, for example, in the Mojave Desert include brush mice, cactus mice, gray fox, porcupine, kangaroo rat, coyote, jack rabbits and many kinds of lizards. In the Australian desert we have Bilby, Perentie, Thorny Devil, Bearded Dragon, Red Kangaroo and Dingo as examples. These animals are adapted to to live in the desert called xerocoles. Many desert animals (and plants) show especially clear evolutionary adaptations for water conservation or heat tolerance, and so often studied in comparative physiology, ecophysiology and evolutionary physiology.
A well studied example is the specializations of mammalian kidneys clear of desert-inhabiting species. Many examples of convergent evolution have been identified in desert organisms, including among cacti and Euphorbia, kangaroo rats and jerboas, Phrynosoma and Moloch lizards. Some flora includes shrubs, Prickly Pears, Desert Holly, and Brittlebush. Most desert plants drought-or salt-tolerant, such xerophytes. Some store water in their leaves, roots and stems. Other desert plants have long taproots that penetrate to the water table if present, or have adapted to the weather by having large fragrant roots to absorb water from a larger area of land. Another adaptation is the development of small, prickly leaves that will look less moisture than deciduous leaves with large areas.
Stems and leaves of some plants lower the surface velocity sand-carrying winds and protect the soil against erosion. Even small fungi and microscopic plant organisms found on the surface (known as cryptobiotic soil) can be a vital link in preventing erosion and providing support to other living organisms. Deserts typically have a vegetation cover is sparse but enormously diverse. The giant Saguaro cacti in the Sonoran Desert provide nests for desert birds and serve as "trees" in the desert. Saguaro grows slowly but can live up to 200 years. When nine years old, they are about 15 centimeters (6 in) high. After about 75 years, developing the cactus their first branches. When full-grown, Saguaro cactus is 15 meters high and weighs as much as 10 tons. They dot the Sonoran and reinforce the general impression of deserts as cactus-rich land. Although cacti are often regarded as characteristic desert plants, other types of plants well adapted to dry environments. They include the pea and sunflower families. Cold deserts have grasses and shrubs as dominant vegetation.
Biodiversity Case Study – The Atacama
Atacama is the driest places on earth and is largely sterile because it is blocked from moisture on both sides of the Andes and the Chilean Coastal Range. The cold Humboldt Current and anti-cyclonic in the Pacific is critical to keep dry climate Atacama. The average rainfall in the Chilean region of Antofagasta is just 1 mm per year. Some weather stations in the Atacama have never received rain. Suggests that Atacama may not have had any significant precipitation from 1570 to 1971. It is so dry that mountains that reach as high as 6,885 meters (22,590 feet) are completely free of glaciers and in the south from 25 ° S to 27 ° S, may have been glacier-free throughout the Quaternary, though permafrost extends down to an altitude of 4400 meters and is continuously over 5600 meters.
Some places in the Atacama receive a marine fog known locally as the Camanchaca providing sufficient moisture for hypolithic algae, lichens and even some cacti. But in the region in the "fog shadow" of the high coastal crest-line, which averages 3,000 meters (10,000 ft) m height for about 100 km (60 miles) south to Antofagasta, the soil has been compared to Mars. Because of its otherworldly appearance, the Atacama has been used as a location for filming Martian scene. Desert was also primarily featured in the 2008 James Bond film Quantum of Solace. In 2003, a team of researchers report in Science magazine titled "Mars-like Soils in the Atacama Desert, Chile and the dry Limit of Microbial Life "in which they overlapped tests used by the Viking 1 and Viking 2 Mars Landers to discover their lives and were unable to detect any signs in Atacama Desert soil. The region may be unique on Earth in this area and is used by NASA to test instruments for future Mars missions. Let us take a closer look at some of the biology of a particular region of Atacama – the nearby Pan de Azucar National Park.
Pan de Azucar NP is divided into two ecosystems: the coastal desert Taltal and steppe desert of the Sierra vicuna Mackenna. There are more than 20 cactus species in the area, especially of the genus Copiapoa The guanaco is the main mammal found in park. Other mammals include Culpeo Fox, Chilla Fox and the European hare. The coastline area is home to marine mammals such as Marine Otter and the South American Sea Lion. Among the birds are Humboldt Penguin and Peruvian pelican. Also reptile species of the genera Tropidurus and Callopistes inhabit the park.
Human User
Mineral Resources
Deserts may contain large quantities of mineral resources over their entire surface. This event in minerals also determines the color. For example is the red color in many desert true by the occurrence of Laterite. . Some mineral deposits also formed, improved, or preserved by geological processes occur in arid lands due to climate. Groundwater seeps ore minerals and redeposit them in zones near the water table. This leaching concentrates these minerals as iron ore, can be extracted. Evaporation in arid lands enriches mineral accumulation in their lakes. Lake beds known as the Playas can be sources of mineral deposits formed by evaporation. Water evaporation in closed basins precipitates minerals such as gypsum, salts (including sodium nitrate and sodium chloride), and borates.
The minerals formed in these evaporites deposits depends of composition and temperature saline waters at the time of deposition. Significant evaporites resources occur in the Great Basin Desert in the United States, mineral deposits made famous of "20-mule teams" that once pulled borax-laden wagons from Death Valley to the railroad. Boron, from borax and borate evaporites, is an essential ingredient in the manufacture of glass, enamel, agricultural chemicals, water softeners, and pharmaceuticals. Borates derived from evaporites deposits at Searles Lake, California and other desert locations. The total value of chemicals produced from Searles Lake substantially exceeds U.S. $ 1 billion of the Atacama Desert in Chile is unique among the deserts of world in its great abundance of saline minerals. Sodium nitrate has been mined for explosives and fertilizer in the Atacama since the middle of the 19th century. Nearly 3 million tonnes was mined during World War II first Visit our group Chile Mining and Power on www.chronosconsulting.com and our other mining articles about Base articles.
Valuable minerals located in arid lands include copper in the USA, Chile, Peru, and Iran, iron and lead zinc ore in Australia, and gold, silver and uranium deposits in Australia and the USA. Nonmetalic Mineral Resources and rocks as beryllium, mica, lithium, clays, pumice, and scoria also occur in arid areas. Sodium carbonate, sulfate, borate, nitrate, lithium, bromine, iodine, calcium, and strontium compounds come from sediments and near-surface saline lakes formed by evaporation of inland waters, often during geologically recent times. Green River Formation of Colorado, Wyoming, and Utah contains alluvial fan deposits and playa evaporites created in a huge lake whose level fluctuated for millions of years. Economics significant instances of Trona, a major source of sodium compounds, and thick layers of oil shale were created in dry environments.
Some of the more productive petroleum areas on Earth found in arid and semi-arid regions of Africa and the Mideast, although the oil fields were originally formed in shallow marine environments. Recent climate changes have placed these reservoirs in a dry environment. It is noteworthy that Ghawar, the world's largest and most productive oilfield is mostly under theEmpty Quarter and Al-Dahnadeserts. For more information see oil out www.chronosoil.com Other oil reservoirs, however, presumed to be Eolian origin and are presently found in humid environments. The Rotliegendes, a hydrocarbon reservoir in the North Sea, is associated with extensive evaporites deposits. Many of the major U.S. hydrocarbon resources may come from Eolian sand. Ancient alluvial fan sequences may also hydrocarbons.
Solar energy resources
Deserts are increasingly seen as sources of solar energy. Negev Desert and the surrounding area including the Arava valley are the sunniest parts of Israel and a little of this land is cultivated, which is why it has become the center of Israeli solar energy industry. David Faiman, a world expert on solar energy, says energy needs in a country like Israel could be met by building solar plants in Negev. Faiman also believes the technology now exists to deliver all the world's electricity needs by 10 percent of the Sahara. Solel has nine fields of solar collectors in the Mojave desert in California, it has recently signed a contract to build the Mojave Solar Park, who will become the world's largest solar power plant.
Human Life in the desert
A desert is a hostile and potentially deadly environment for unprepared humans. In hot deserts, high temperatures cause rapid loss of water due to sweating, and lack of water sources to rebuild it can result in dehydration and death within a few days. Moreover, unprotected people also suffered from heat stroke. People may also have to adapt sandstorms in some deserts, not only in their negative effects on the respiratory tract and eyes, but also in their potentially harmful effects on equipment such as filters, vehicles and communications equipment. Sand storms can last several hours, sometimes even days. This makes surviving in the desert quite difficult for humans. Despite this, some cultures made hot desert their homes for thousands of years, including Bedouin, Tuareg and Pueblo people.
Modern technology, including advanced irrigation systems, desalinization and air conditioning have made deserts much more hospitable. In the United States and Israel for example, desert farming found widespread use and places like Las Vegas owes much to the air conditioning. In cold deserts, hypothermia and frostbite are the chief hazards and dehydration in the absence of a heat source to melt ice for drinking water. Falling through the pack ice or surface ice layer in ice-cold water is a particular danger requiring emergency measures to prevent rapid hypothermia. Hunger is also a danger at low temperatures the body requires much more food energy to maintain body heat and move. As with hot deserts. Some people like the Inuit have adapted to the harsh conditions of cold deserts, most traditional life in desert are nomadic. It depends in hot deserts to find water, and the following rare rainfall for grazing by livestock. In cold deserts, depends that of finding good hunting and fishing grounds for shelter from snowstorms and winter extremes, and storing enough food for the winter. Permanent solution in both kinds of deserts requires permanent water and food sources and appropriate shelter, or the technology and energy sources to provide it. Many deserts are flat and featureless, lacking landmarks, or composed of repeating landforms, such as sand dunes or messy ice-fields of glaciers. Advanced skills or equipment are required to navigate through these landscapes and the inexperienced traveler may perish if supplies run out after being dropped. In addition, sand storms or snowstorms can cause disorientation in highly reduced visibility.
The danger of wild animals in the desert have been in the explorers' accounts but does not cause a higher death than in other environments such as rain forests or savannah woodland, and generally not as even affect human distribution. Defence against polar bears may be advisable in some areas of the Arctic that can be precautions against poisonous snakes and scorpions in choice locations where to camp for some hot deserts. But it is hard to overestimate the importance of deserts in our cultural and historical background. Three of the world's largest religions, Christianity, Islam and Judaism began and is located on a desert backdrop. All three religions are monotheistic and today have enormous geopolitical influence extends far beyond their origin area, see articles on Christianity here at Article Base and Biblon www.biblon.com. Deserts are now also an important source of tourism and travel interests such as Joshua Tree, Death Valley National Parks and crucial to the film industry.
Deserts are also vital areas of scientific interest. – Specific examples include Deep Canyon on the western edge of Colorado Desert is associated with the University of California, Riverside is located in PL Boyd Deep Canyon Desert Research Center. It receives a number of visiting scientists and students, and in addition to research, addresses conservation issues from the surrounding environment, such as the fate of small-toed lizard. Another desert center established by a visionary biologist, is Gobabeb Training and Research Centre, located in Namibia in the driest part of the coastal Namib Desert in the Namib-Naukluft Park. The United Nations Environment Programme concludes that "People have lived in deserts for millennia as hunter-gatherers, farmers and livestock breeders, and some people still do it today. But other people now live in urban development located in deserts, or enjoy deserts temporarily for tourism and leisure. But others are extracting profits from mining or other non-renewable resource. Deserts are a large and probably growing environment globally, and their future will be better supported if it is based on a thorough understanding of their structure and function, and influence of people's activities in the past, present and future. "
Dr Simon Harding
www.chronosconsulting.com
www.coberongreen.com
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