Tundra
In physical geography, tundra is a type of biome where the tree growth is hindered by low temperatures and short growing seasons. The term tundra comes through Russian тундра from the Kildin Sami word tūndâr uplands, there are three types of tundra, Arctic tundra, alpine tundra, and Antarctic tundra. In tundra, the vegetation is composed of shrubs and grasses, mosses. Scattered trees grow in tundra regions. The ecotone between the tundra and the forest is known as the line or timberline. Arctic tundra occurs in the far Northern Hemisphere, north of the taiga belt, the word tundra usually refers only to the areas where the subsoil is permafrost, or permanently frozen soil. Permafrost tundra includes vast areas of northern Russia and Canada, the polar tundra is home to several peoples who are mostly nomadic reindeer herders, such as the Nganasan and Nenets in the permafrost area. Arctic tundra contains areas of landscape and is frozen for much of the year. The soil there is frozen from 25–90 cm down, and it is impossible for trees to grow, instead and sometimes rocky land can only support low growing plants such as moss and lichen.
There are two seasons and summer, in the polar tundra areas. During the winter it is cold and dark, with the average temperature around −28 °C. However, extreme temperatures on the tundra do not drop as low as those experienced in taiga areas further south. During the summer, temperatures rise somewhat, and the top layer of seasonally-frozen soil melts, the tundra is covered in marshes, lakes and streams during the warm months. Generally daytime temperatures during the rise to about 12 °C. Arctic tundras are sometimes the subject of conservation programs. In Canada and Russia, many of areas are protected through a national Biodiversity Action Plan. Tundra tends to be windy, with winds often blowing upwards of 50–100 km/h, however, in terms of precipitation, it is desert-like, with only about 15–25 cm falling per year. Although precipitation is light, evaporation is relatively minimal, there is a natural pattern of accumulation of fuel and wildfire which varies depending on the nature of vegetation and terrain
Biodiversity
Biodiversity, a contraction of biological diversity, generally refers to the variety and variability of life on Earth. One of the most widely used definitions defines it in terms of the variability within species and it is a measure of the variety of organisms present in different ecosystems. This can refer to genetic variation, ecosystem variation, or species variation within an area, terrestrial biodiversity tends to be greater near the equator, which seems to be the result of the warm climate and high primary productivity. Biodiversity is not distributed evenly on Earth, and is richest in the tropics and these tropical forest ecosystems cover less than 10 per cent of earths surface, and contain about 90 percent of the worlds species. Marine biodiversity tends to be highest along coasts in the Western Pacific, there are latitudinal gradients in species diversity. Biodiversity generally tends to cluster in hotspots, and has been increasing through time, the number and variety of plants and other organisms that exist is known as biodiversity.
It is a component of nature and it ensures the survival of human species by providing food, shelter, medicines. The richness of biodiversity depends on the conditions and area of the region. All species of plants taken together are known as flora and about 300,000 species of plants are known to date, all species of animals taken together are known as fauna which includes birds, fish, insects, molluscs, etc. Rapid environmental changes typically cause mass extinctions, more than 99 percent of all species, amounting to over five billion species, that ever lived on Earth are estimated to be extinct. Estimates on the number of Earths current species range from 10 million to 14 million, of which about 1.2 million have been documented and over 86 percent have not yet been described. More recently, in May 2016, scientists reported that 1 trillion species are estimated to be on Earth currently with only one-thousandth of one percent described, the total amount of related DNA base pairs on Earth is estimated at 5.0 x 1037 and weighs 50 billion tonnes.
In comparison, the mass of the biosphere has been estimated to be as much as 4 TtC. In July 2016, scientists reported identifying a set of 355 genes from the Last Universal Common Ancestor of all living on Earth. The age of the Earth is about 4.54 billion years old, there are microbial mat fossils found in 3.48 billion-year-old sandstone discovered in Western Australia. Other early physical evidence of a substance is graphite in 3.7 billion-year-old meta-sedimentary rocks discovered in Western Greenland. More recently, in 2015, remains of life were found in 4.1 billion-year-old rocks in Western Australia. According to one of the researchers, If life arose relatively quickly on Earth, it could be common in the universe
Gobi Desert
The Gobi Desert is a large desert region in Asia. It covers parts of northern and northwestern China, and of southern Mongolia, the Gobi is most notable in history as part of the great Mongol Empire, and as the location of several important cities along the Silk Road. The Gobi is a rain shadow desert, formed by the Himalayan mountain range blocking rain-carrying clouds from the Indian Ocean reaching the Gobi territory, the Gobi measures over 1,600 km from southwest to northeast and 800 km from north to south. The desert is widest in the west, along the joining the Lake Bosten. It occupies an arc of land 1,295,000 km2 in area as of 2007, it is the fifth-largest desert in the world, much of the Gobi is not sandy but has exposed bare rock. The Gobi is a desert, with frost and occasionally snow occurring on its dunes. Besides being quite far north, it is located on a plateau roughly 910–1,520 metres above sea level. An average of approximately 194 millimetres of rain falls annually in the Gobi, additional moisture reaches parts of the Gobi in winter as snow is blown by the wind from the Siberian Steppes.
These winds cause the Gobi to reach extremes of temperature ranging from −40 °C or −40 °F in winter to 45 °C or 113 °F in summer, the climate of the Gobi is one of great extremes, combined with rapid changes of temperature of as much as 35 °C. These can occur not only seasonally but within 24 hours, in southern Mongolia, the temperature has been recorded as low as −32.8 °C. In contrast, in Alxa, Inner Mongolia, it rises as high as 37 °C in July, average winter minimums are a frigid −25 °C while summertime temperatures are warm to hot, with highs that range up to 50 °C. Most of the falls during the summer. Hence, the icy sandstorms and snowstorms of spring and early summer plus early January, the Gobi Desert is the source of many important fossil finds, including the first dinosaur eggs. They are occasionally visited by snow leopards, brown bears, drought-adapted shrubs in the desert included gray sparrows saltwort, gray sagebrush, and low grasses such as needle grass and bridlegrass. Several large nature reserves have established in the Gobi, including Gobi Gurvansaikhan National Park, Great Gobi A.
The area is vulnerable to trampling by livestock and off-road vehicles, in Mongolia, grasslands have been degraded by goats, which are raised by nomadic herders as source of cashmere wool. The economic trends of livestock privatization and the collapse of the economy have caused people to return to subsistence rural lifestyles. Large copper and gold deposits located at Oyuu Tolgoi, about 80 kilometres from the Chinese border into Mongolia, are being investigated for development as mining operations
Desert
A desert is a barren area of land where little precipitation occurs and consequently living conditions are hostile for plant and animal life. The lack of vegetation exposes the unprotected surface of the ground to the processes of denudation, about one third of the land surface of the world is arid or semi-arid. This includes much of the regions where little precipitation occurs. Deserts can be classified by the amount of precipitation falls, by the temperature that prevails. Deserts are formed by weathering processes as large variations in temperature between day and night put strains on the rocks which consequently break in pieces, although rain seldom occurs in deserts, there are occasional downpours that can result in flash floods. Rain falling on hot rocks can cause them to shatter and the resulting fragments and this picks up particles of sand and dust and wafts them aloft in sand or dust storms. Wind-blown sand grains striking any solid object in their path can abrade the surface, rocks are smoothed down, and the wind sorts sand into uniform deposits.
The grains end up as level sheets of sand or are piled high in billowing sand dunes, other deserts are flat, stony plains where all the fine material has been blown away and the surface consists of a mosaic of smooth stones. These areas are known as desert pavements and little further erosion takes place, other desert features include rock outcrops, exposed bedrock and clays once deposited by flowing water. Temporary lakes may form and salt pans may be left when waters evaporate, there may be underground sources of water in the form of springs and seepages from aquifers. Where these are found, oases can occur and animals living in the desert need special adaptations to survive in the harsh environment. Plants tend to be tough and wiry with small or no leaves, water-resistant cuticles, some annual plants germinate and die in the course of a few weeks after rainfall while other long-lived plants survive for years and have deep root systems able to tap underground moisture. Animals need to cool and find enough food and water to survive.
Many are nocturnal and stay in the shade or underground during the heat of the day and they tend to be efficient at conserving water, extracting most of their needs from their food and concentrating their urine. Some animals remain in a state of dormancy for long periods and they reproduce rapidly while conditions are favorable before returning to dormancy. People have struggled to live in deserts and the surrounding lands for millennia. Nomads have moved their flocks and herds to wherever grazing is available, the cultivation of semi-arid regions encourages erosion of soil and is one of the causes of increased desertification. Many trade routes have been forged across deserts, especially across the Sahara Desert, large numbers of slaves were taken northwards across the Sahara
Ephemerality
Ephemerality is the concept of things being transitory, existing only briefly. Because different people may value the passage of time differently, the concept of ephemerality is a relative one, an ephemeral waterbody is a wetland, stream, pond or lake that only exists for a short period following precipitation or snowmelt. They are not the same as intermittent or seasonal waterbodies, which exist for longer periods, examples of ephemeral streams are the Luni river in Rajasthan, Ugab River in Southern Africa, and a number of small ephemeral watercourses that drain Talak in northern Niger. Other notable ephemeral rivers include the Todd River and Sandover River in Central Australia as well as the Son River, Batha River, any endorheic basin, or closed basin, that contains a playa or dry lake at its drainage lowpoint can become an ephemeral lake. Examples include Lake Carnegie in Western Australia, Lake Cowal in New South Wales, Mystic Lake and Rogers Lake in California, even the driest and lowest place in North America, Death Valley, became flooded with a short-lived ephemeral lake in the spring of 2005.
There are ephemeral islands such as Banua Wuhu and Home Reef and these islands appear when volcanic activity increases their height above sea level, but disappear over several years due to wave erosion. Bassas da India, on the hand, is a near-sea level island that appears only at low tide. Many plants are adapted to a lifestyle, in which they spend most of the year or longer as seeds before conditions are right for a brief period of growth. The spring ephemeral plant mouse-ear cress is a well-known example, animals can be ephemeral, with brine shrimp and the mayfly being examples. The placenta is considered an ephemeral organ present during gestation and pregnancy, ephemeral can be used as an adjective to refer to a fast-deteriorating importance or temporary nature of an object to a person. Brands are notoriously ephemeral assets, and magazine publishing was once much more ephemeral than it is today, a number of art forms can be considered ephemeral because of their temporary nature. Early land art and all sand sculptures, ice sculptures and chalk drawings on footpaths are examples of ephemeral art, G.
Augustine Lynas and Duthain Dealbh create ephemeral sculptures. Ephemeroptera Christine Buci-Glucksmann, Esthetique De Lephemere, Galilee, ISBN 2-7186-0622-3
Earth
Earth, otherwise known as the World, or the Globe, is the third planet from the Sun and the only object in the Universe known to harbor life. It is the densest planet in the Solar System and the largest of the four terrestrial planets, according to radiometric dating and other sources of evidence, Earth formed about 4.54 billion years ago. Earths gravity interacts with objects in space, especially the Sun. During one orbit around the Sun, Earth rotates about its axis over 365 times, Earths axis of rotation is tilted, producing seasonal variations on the planets surface. The gravitational interaction between the Earth and Moon causes ocean tides, stabilizes the Earths orientation on its axis, Earths lithosphere is divided into several rigid tectonic plates that migrate across the surface over periods of many millions of years. About 71% of Earths surface is covered with water, mostly by its oceans, the remaining 29% is land consisting of continents and islands that together have many lakes and other sources of water that contribute to the hydrosphere.
The majority of Earths polar regions are covered in ice, including the Antarctic ice sheet, Earths interior remains active with a solid iron inner core, a liquid outer core that generates the Earths magnetic field, and a convecting mantle that drives plate tectonics. Within the first billion years of Earths history, life appeared in the oceans and began to affect the Earths atmosphere and surface, some geological evidence indicates that life may have arisen as much as 4.1 billion years ago. Since then, the combination of Earths distance from the Sun, physical properties, in the history of the Earth, biodiversity has gone through long periods of expansion, occasionally punctuated by mass extinction events. Over 99% of all species that lived on Earth are extinct. Estimates of the number of species on Earth today vary widely, over 7.4 billion humans live on Earth and depend on its biosphere and minerals for their survival. Humans have developed diverse societies and cultures, the world has about 200 sovereign states, the modern English word Earth developed from a wide variety of Middle English forms, which derived from an Old English noun most often spelled eorðe.
It has cognates in every Germanic language, and their proto-Germanic root has been reconstructed as *erþō, earth was written in lowercase, and from early Middle English, its definite sense as the globe was expressed as the earth. By early Modern English, many nouns were capitalized, and the became the Earth. More recently, the name is simply given as Earth. House styles now vary, Oxford spelling recognizes the lowercase form as the most common, another convention capitalizes Earth when appearing as a name but writes it in lowercase when preceded by the. It almost always appears in lowercase in colloquial expressions such as what on earth are you doing, the oldest material found in the Solar System is dated to 4. 5672±0.0006 billion years ago. By 4. 54±0.04 Gya the primordial Earth had formed, the formation and evolution of Solar System bodies occurred along with the Sun
Atacama Desert
The Atacama Desert is a plateau in South America, covering a 1, 000-kilometre strip of land on the Pacific coast, west of the Andes mountains. It is the driest non-polar desert in the world, according to estimates, the Atacama Desert proper occupies 105,000 square kilometres, or 128,000 square kilometres if the barren lower slopes of the Andes are included. Most of the desert is composed of terrain, salt lakes, sand. The National Geographic Society considers the area of southern Peru to be part of the Atacama Desert. Peru borders it on the north and the Chilean Matorral ecoregion borders it on the south, to the east lies the less arid Central Andean dry puna ecoregion. The drier portion of this ecoregion is located south of the Loa River between the parallel Sierra Vicuña Mackenna and Cordillera Domeyko, to the north of the Loa lies the Pampa del Tamarugal. The Coastal Cliff of northern Chile west of the Chilean Coast Range is the topographic feature of the coast. The geomorphology of the Atacama Desert has been characterized as a low-relief bench similar to a giant uplifted terrace by Armijo and co-workers.
The intermediate depression forms a series of basins in much of Atacama Desert south of latitude 19°30’ S. North of this latitude the intermediate depression drains into the Pacific Ocean. Although the almost total lack of precipitation is the most prominent characteristic of the Atacama Desert, in 2012, the altiplano winter brought floods to San Pedro de Atacama. On 25 March 2015, heavy rainfall affected the part of the Atacama desert. Resulting floods triggered mudflows that affected the cities of Copiapo, Tierra Amarilla, Chanaral, the Atacama Desert is commonly known as the driest non-polar place in the world, especially the surroundings of the abandoned Yungay town. The average rainfall is about 15 mm per year, although some locations, such as Arica and Iquique, some weather stations in the Atacama have never received rain. Periods of up to four years have been registered with no rainfall in the sector, delimited by the cities of Antofagasta and Copiapó. Evidence suggests that the Atacama may not have had any significant rainfall from 1570 to 1971, the Atacama Desert may be the oldest desert on earth, and has experienced extreme hyperaridity for at least 3 million years, making it the oldest continuously arid region on earth.
The long history of aridity raises the possibility that supergene mineralisation, under the conditions, can form in arid environments. This desert is so arid, many mountains higher than 6,000 m are free of glaciers. Only the highest peaks have some permanent snow coverage, the southern part of the desert, between 25 and 27°S, may have been glacier-free throughout the Quaternary, though permafrost extends down to an altitude of 4,400 m and is continuous above 5,600 m
Xeriscaping
Xeriscaping is landscaping and gardening that reduces or eliminates the need for supplemental water from irrigation. It is promoted in regions that do not have easily accessible, plentiful, or reliable supplies of fresh water, Xeriscaping may be an alternative to various types of traditional gardening. In some areas, terms as water-conserving landscapes, drought-tolerant landscaping, plants whose natural requirements are appropriate to the local climate are emphasized, and care is taken to avoid losing water to evaporation and run-off. The specific plants used in xeriscaping depend upon the climate, Xeriscaping is different from natural landscaping, because the emphasis in xeriscaping is on selection of plants for water conservation, not necessarily selecting native plants. Public perception of xeriscaping has frequently been negative as many assume that these types of landscapes are ugly expanses of cactus, studies have shown that education in water conservation practices in the landscape can greatly improve the publics perception of xeriscaping.
The term zero-scaping or zeroscaping is sometimes substituted for xeriscaping due to phonetic similarity, when used seriously, zero-scaping usually refers to a different type of low-water landscaping that is often devoid, or nearly devoid of plants. Because the term was derived from the Greek root xeros, xeriscaping is sometimes misspelled xeroscaping, lowered consumption of water, Xeriscaped landscapes use up to two thirds less water than regular lawn landscapes. Makes more water available for domestic and community uses and the environment. Reduce Maintenance, Aside from occasional weeding and mulching Xeriscaping requires far less time, Xeriscape plants in appropriate planting design, and soil grading and mulching, takes full advantage of rainfall retention. Less cost to maintain, Xeriscaping requires less fertilisers and equipment, reduced waste and pollution, Lawn clippings can contribute to organic waste in landfills and the use of heavy fertilisers contributes to urban runoff pollution.
Xeriscape style may not conform to local aesthetics, Some homeowners associations have rules requiring a certain percentage of land to be used as lawns. Refutation, Because of drought and improved education, these rules either have been or are in the process of being overturned in many areas. Xeriscape contains hazardous plants, Some styles of xeriscaping include plants such as cacti and agave having thorns or serrated edges that may harm pets, There are many xeric plants that possess no sharp points, and many familiar plants like rose bushes and raspberry plants have thorns. Xeriscape installation cost is high, If a non-xeric landscape was originally present, For new construction, xeric landscaping can cost much less than a lawn. Whether new or a replacement, the water-saving cost benefit of a xeric landscape over a one is self-evident. Over time the cost savings can pay for the installation, in arid and semi-arid areas, drought-based water restrictions may necessitate the reduction of turf areas that would be likely to die due to a lack of water already occurring because of the drought.
Originally conceived by Denver Water, the seven principles of xeriscaping have since expanded into simple and applicable concepts to creating landscapes that use less water. Plan and design, Create a diagram, drawn to scale, once a base plan of an existing site has been determined, the creation of a conceptual plan that shows the areas for turf, perennial beds, screens, etc. is undertaken
Interglacial
An interglacial period is a geological interval of warmer global average temperature lasting thousands of years that separates consecutive glacial periods within an ice age. The current Holocene interglacial began at the end of the Pleistocene and these long glacial periods were separated by more temperate and shorter interglacials. During interglacials, such as the present one, the climate warms, forests return to areas that once supported tundra vegetation. Interglacials are identified on land or in shallow epicontinental seas by their paleontology and faunal remains of species pointing to temperate climate and indicating a specific age are used to identify particular interglacials. Commonly used are mammalian and molluscan species and plant macro-remains, many other fossil remains may be helpful, ostracods, diatoms, etc. Recently, ice cores and ocean sediment cores provide more quantitative and accurately dated evidence for temperatures, the interglacials and glacials coincide with cyclic changes in the Earths orbit.
Three orbital variations contribute to interglacials, the first is a change in the Earths orbit around the sun, or eccentricity. The second is a shift in the tilt of the Earths axis, the third is precession, or wobbling motion of Earths axis. Warm summers in the Southern hemisphere occur when that hemisphere is tilted toward the sun, cool summers occur when the Earth is farthest from the sun during that season. These effects are more pronounced when the eccentricity of the orbit is large, when the obliquity is large, seasonal changes are more extreme. Interglacials are a tool for geological mapping and for anthropologists. Brief periods of climate that occurred during the last glacial are called interstadials. Most interstadials are shorter than interglacials, Interstadial climate may have been relatively warm but this is not necessarily so. Because the colder periods have often very dry, wetter periods have been registered in the sedimentary record as interstadials as well. The oxygen isotope ratio obtained from seabed sediment core samples, a proxy for average global temperature, is an important source of information about changes in the climate of the earth.
The climatic optimum of an interglacial follows, and is followed by, phases that are within the same interglacial, during an interglacial optimum, sea levels rise to their highest values, but not necessarily exactly at the same time as the climatic optimum. In the present interglacial, the Holocene, the climatic optimum occurred during the Subboreal and our current climatic phase following this climatic optimum is still within the same interglacial. This warm period was followed by a decline until about 2,000 years ago
Sahara
The Sahara is the largest hot desert and the third largest desert in the world after Antarctica and the Arctic. Its area of 9,200,000 square kilometres is comparable to the area of the United States. The desert comprises much of North Africa, excluding the fertile region on the Mediterranean Sea coast, the Atlas Mountains of the Maghreb, and the Nile Valley in Egypt and Sudan. It stretches from the Red Sea in the east and the Mediterranean in the north to the Atlantic Ocean in the west, where the landscape gradually changes from desert to coastal plains. To the south, it is bounded by the Sahel, a belt of tropical savanna around the Niger River valley. The Sahara can be divided into several regions including, the western Sahara, the central Ahaggar Mountains, the Tibesti Mountains, the Aïr Mountains, the Ténéré desert, the name Sahara is derived from ṣaḥārā, the plural of the Arabic word for desert. The Sahara covers large parts of Algeria, Egypt, Mali, Morocco, Western Sahara, Sudan and it covers 9 million square kilometres, amounting to 31% of Africa.
If all areas with an annual precipitation of less than 250 mm were included. It is one of three physiographic provinces of the African massive physiographic division. The Sahara is mainly rocky hamada, Ergs form only a minor part, wind or rare rainfall shape the desert features, sand dunes, dune fields, sand seas, stone plateaus, gravel plains, dry valleys, dry lakes, and salt flats. Unusual landforms include the Richat Structure in Mauritania, several deeply dissected mountains, many volcanic, rise from the desert, including the Aïr Mountains, Ahaggar Mountains, Saharan Atlas, Tibesti Mountains, Adrar des Iforas, and the Red Sea hills. The highest peak in the Sahara is Emi Koussi, a volcano in the Tibesti range of northern Chad. The central Sahara is hyperarid, with sparse vegetation, the northern and southern reaches of the desert, along with the highlands, have areas of sparse grassland and desert shrub, with trees and taller shrubs in wadis, where moisture collects. In the central, hyperarid region, there are subdivisions of the great desert, the Ténéré, the Libyan Desert, the Eastern Desert.
These extremely arid areas often receive no rain for years, the northern limit corresponds to the 100 mm isohyet of annual precipitation. To the south, the Sahara is bounded by the Sahel, the southern limit of the Sahara is indicated botanically by the southern limit of Cornulaca monacantha, or northern limit of Cenchrus biflorus, a grass typical of the Sahel. According to climatic criteria, the limit of the Sahara corresponds to the 150 mm isohyet of annual precipitation. The Sahara is the worlds largest low-latitude hot desert and this steady descending airflow causes a warming and a drying effect in the upper troposphere
Desertification
Desertification is a type of land degradation in which relatively dry area of land becomes increasingly arid, typically losing its bodies of water as well as vegetation and wildlife. It is caused by a variety of factors, such as climate change. Desertification is a significant global ecological and environmental problem, considerable controversy exists over the proper definition of the term desertification for which Helmut Geist has identified more than 100 formal definitions. Another major contribution to the controversy comes from the sub-grouping of types of desertification, the worlds most noted deserts have been formed by natural processes interacting over long intervals of time. During most of times, deserts have grown and shrunk independent of human activities. Paleodeserts are large sand seas now inactive because they are stabilized by vegetation, some extending beyond the present margins of deserts, such as the Sahara. Drylands occupy approximately 40–41% of Earth’s land area and are home to more than 2 billion people.
As of 1998, the then-current degree of expansion of the Sahara was not well known, due to a lack of recent. Causes of desertification in Sahel, The impact of global warming, in this area, the level of desertification is very high compared to other areas in the world. All areas situated in the part of Africa are characterized by a dry climate, hot temperatures. So, droughts are the rule in the Sahel region, development of the desertification process in Sahel, Some studies have shown that Africa has lost approximately 650000 km² of its productive agricultural land over the past 50 years. The propagation of desertification in this area is considerable, Some statistics have shown that since 1900, the Sahara has expanded by 250 km, covering an additional area of 6000 square kilometers. Impacts of desertification in Sahel, The survey, done by the institute for development, had demonstrated that this dryness is spreading fast in the Sahelian countries. Desertification in the Sahel can affect more than one billion of its inhabitants, 70% of the arid area has deteriorated and water resources have disappeared, leading to soil degradation.
The loss of topsoil means that plants take root firmly. The United Nations Convention says that six million Sahelian citizens would have to give up the desertified zones of sub-Saharan Africa for North Africa. As the desertification takes place, the landscape may progress through different stages, on gradually sloped terrain, desertification can create increasingly larger empty spaces over a large strip of land, a phenomenon known as Brousse tigrée. A mathematical model of this phenomenon proposed by C, klausmeier attributes this patterning to dynamics in plant-water interaction
Chihuahuan Desert
The Chihuahuan Desert is a desert and ecoregion designation covering parts of Mexico and the United States. It occupies much of West Texas and parts of southern New Mexico and it is bordered on the west by the extensive Sierra Madre Occidental range, along with northern portions of the Sierra Madre Oriental range. With an area of about 362,000 km2, it is the third largest desert of the Western Hemisphere and the second largest in North America, after the Great Basin Desert. There are a few areas within the desert, the largest is Ciudad Juárez with almost two million inhabitants and Torreón, the US cities of El Paso and Albuquerque. Las Cruces and Roswell are among the significant cities in this ecoregion. Saltillo and Santa Fe are located near the Chihuahuan desert, according to the World Wide Fund for Nature the Chihuahuan Desert may be the most biologically diverse desert in the world as measured by species richness or endemism. The region has been degraded, mainly due to grazing. Many native grasses and other species have become dominated by native plants, including creosote bush and mesquite, due to overgrazing.
The Mexican wolf, once abundant, has been extirpated, the desert has a dry climate with only one rainy season in the summer and smaller amounts of precipitation in early winter. Most of the summer rains falls between late June and early October, during the North American Monsoon when moist air from the Gulf of Mexico penetrates into the region, the average annual temperature in the desert is 24 °C, which varies with altitude. The hottest temperatures in the occur in lower elevation areas. Northern areas have more severe winters than the portion and can receive snowstorms. The mean annual precipitation for the Chihuahuan Desert is 235 mm with a range of approximately 150–400 mm, nearly two-thirds of the arid zone stations have annual totals between 225 and 275 mm. Snowfall is scant except at the higher elevation edges, the desert is fairly young, existing for only 8000 years. Creosote bush is the dominant plant species on gravelly and occasional sandy soils in areas within the Chihuahuan Desert.
The other species it is found depends on factors such as the soil, altitude. Viscid acacia, and tarbush dominate northern portions, as does broom dalea on sandy soils in western portions and Opuntia species are abundant in foothill edges and the central third, while Arizona rainbow cactus and Mexican fire-barrel cactus inhabit portions near the US–Mexico border. Herbaceous plants, such as muhly, blue grama, gypsum grama
This article incorporates text available under the CC BY-SA 3.0 license. World Wide Fund for Nature. "Deserts and Xeric Shrubland Ecoregions". Archived from the original on 2012-04-25.
