Geography of Australia: geology, climate, deserts, water bodies, natural resources, ecology and population. Deserts and semi-deserts - climate, wildlife and vegetation Tropical deserts of Australia animals and plants
The most arid central regions of the mainland occupy the largest areas of Australia. Here are various types of territories, from loose sands, salt marshes, rubble rocky areas to spiny forests. However, two groups dominate: 1) the acacia mulga-scrub formation; 2) a formation dominated by spinifex grass, or triodnium. The latter dominates in the most deserted central regions.
Acacia shrubs and undersized (3-5 m) tree-shrub deserts and semi-deserts are similar in nature to the dry prickly woodlands of Somalia or the Kalahari on the African continent. The northern variants of these groups with a short summer wet period and an abundance of tall termite mounds can also be considered as the extreme arid version of the savanna and light forest zone. The dominant plant almost everywhere is ours - veinless acacia - and other phyllodes. The number of eucalyptus and casuarina is small, they are confined to dry riverbeds and extensive depressions with a close occurrence of groundwater. The grass cover is often almost absent or represented by very sparse groups of grasses, saltworts, and other leafy succulents.
The sandy areas in the center and west of the continent are covered with thickets of extremely xeromorphic hard grasses from the genus triodia. In Queensland and New South Wales, prickly pear cactus has proliferated and become a noxious weed. Prickly pear was brought from South America in the 80s of the last century and settled on an area of about 24 million hectares.
Unlike the Sahara and the Namib, in the deserts of Australia there are no significant areas of "absolute" deserts, practically free from higher plants. In drainless basins and along the shores of salt lakes, halophytic formations are developed, formed by special species of widespread ancient genera (saltwort, quinoa, parnolistnik, prutnyak, saltpeter). Shober's saltpeter also grows in the semi-deserts of Eurasia. The Nullarbor Plain adjoining the Great Australian Bight has semi-desert vegetation, already developing in a subtropical, close to temperate climate. It is dominated by high (up to 1.5 m) bushes of various halophytes - representatives of haze (hospice, quinoa, etc.), which are considered a good fodder plant for sheep. On the plain, due to the wide distribution of karst phenomena, there are almost no surface water bodies.
Some botanists believe that real deserts in Australia are almost never found, and semi-deserts predominate. Indeed, the density of vegetation in the arid regions of the mainland is usually relatively large, which is associated with a regular short wet season. The annual amount of precipitation is nowhere below 100 mm, but usually it is close to 200-300 mm. In addition, in many places there is a shallow water-resistant horizon, where the moisture available to the roots of plants is stored for a long time.
Animal world. In the faunistic aspect, the fauna of the arid interior regions of Australia as a whole is a depleted variant of dry savanna and light forest groups. Most of the species are found both in deserts and savannahs, although a number of groups of animals are especially numerous in desert and semi-desert habitats. Of the mammals, such typical animals include the marsupial mole, the marsupial jerboa, comb-tailed marsupial mice and the comb-tailed marsupial rat. The entire central and western parts of the mainland are inhabited by large red kangaroos. These animals are numerous in many places and are considered undesirable competitors of sheep. The same applies to smaller types of wallabies. Of the smallest species of the kangaroo family (less than a rabbit), kangaroo rats are interesting for their ability to carry a "load" - an armful of grass, clasping it with their long tail. Many species of kangaroo rats widely inhabited almost the entire continent, but are now heavily exterminated by introduced dogs and foxes, and also displaced by rabbits, which inhabit and destroy their original habitats. Therefore, now they are better preserved precisely in desert regions, where the influence of introduced animals is less felt. Here the most common dog is the dingo. In some areas, feral one-humped camels bred, brought to the mainland in the last century as a vehicle on expeditions.
The most famous bird of the semi-desert regions of the mainland is the emu. This is the only species (sometimes two closely related species are distinguished) of a special family related to cassowaries. In all arid regions, weavers and small parrots are common, feeding on seeds of cereals (including triodia). These are the already mentioned zebra finches, budgerigars, and also nymph parrots. All these species nest in the hollows of dry trees. The nocturnal parrot is very typical for arid regions. It is indeed a nocturnal bird. She spends most of her time on the ground, the basis of nutrition is the seeds of the trio. Unlike most other parrots, the nocturnal one does not nest in hollows, but among thickets of prickly grasses.
Of the vertebrates, various reptiles are especially characteristic of the desert and semi-desert, of which lizards of the agamic, skink and monitor lizard families predominate. The scale-legged family characteristic of Australia, which includes snake-like lizards with reduced limbs, also has desert representatives. Among the agamas in the tropical northern regions of dry woodlands and semi-deserts, there are frilled lizards, which are also characteristic of the savannah. Species of this genus have the ability to run on two hind limbs. This way of movement was inherent in some Mesozoic dinosaurs. Several species of bearded lizards, similar to our common dragons, live in the deserts. The most original appearance of Moloch. This small, up to 20 cm, flat lizard is covered with outgrowths and spikes. Moloch's skin can absorb moisture. In lifestyle and appearance, it resembles American desert toad lizards. The basis of nutrition of Moloch is ants.
Skinks are represented mainly by genera endemic to Australia (sometimes including New Zealand), whose species live both in deserts and in other zones. There are especially many species of the endemic genus Ctenotus - small graceful lizards with smooth scales.
The exceptional originality and antiquity of the flora and fauna of Australia is explained by its long isolation. Most plant species (75%) and animals (90%) of Australia are endemic, that is, they are not found anywhere else in the world. There are few mammals among the animals, however, species extinct on other continents, including marsupials (about 160 species), have survived. Characteristic representatives of the Australian flora are eucalyptus (600 species), acacia (490 species) and casuarina. The mainland did not give the world valuable cultivated plants.
Australia is located in four geographical zones - from subequatorial to temperate. The change in natural zones is due to changes in temperature and precipitation patterns. The flat nature of the relief contributes to a well-defined, disturbed only in the east. The main part of the continent lies in tropical latitudes, therefore, tropical deserts and semi-deserts, occupying half the area of the mainland, have received the greatest development.
The central parts of the mainland in two geographical zones (tropical and subtropical) are occupied by deserts and semi-deserts. Australia is rightly called the continent of deserts (Great Sandy, Great Victoria Desert, Gibson Desert, etc.). Tropical deserts and semi-deserts dominate the Western Australian Plateau in a tropical continental climate. In stony and sandy riverbeds, thin forests of casuarinas stretch along the riverbeds. In the hollows of clayey semi-deserts, there are thickets of quinoa and salt-tolerant species of acacia and eucalyptus. Deserts are characterized by "pillows" of bushy cereal spinifex. Soils of semi-deserts are gray soils, deserts are primitive stony, clayey or sandy.
In the south of the mainland in the subtropics, deserts and semi-deserts occupy the Nullarbor plain (“treeless”) and the Murray-Darling lowland. They are formed in a subtropical continental climate on brown semi-desert and gray-brown soils. Against the background of dry rare cereals, wormwood and saltwort are found, tree and shrub vegetation is absent.
The shortage problem is the most acute in Australia. Previously, it was solved by pumping groundwater from numerous wells. But at present, a decrease in the water level in artesian basins has been recorded. The depletion of underground water reserves, along with a decrease in the full flow of rivers, has exacerbated the shortage of water in Australia, forcing the implementation of programs to conserve it.
One of the ways to preserve nature is the creation of specially protected natural areas. They occupy 11% of the area of the continent. One of the most visited is the Kosciuszko park in the Australian. In the north is one of the largest parks in the world - Kakadu, where not only wetlands are taken under protection, which serve as a habitat for many endemic birds, but also caves with Aboriginal rock art. In the Blue Mountains Park, stunning mountain landscapes with a variety of eucalyptus forests are protected. The nature of deserts has also been taken under protection (parks Great Victoria Desert, Simpson Desert). Ayers Rock, a giant red sandstone monolith sacred to the aborigines, has been recognized as a UNESCO World Heritage Site in Uluru-Katayuta Park. The fabulous world of corals is protected in the underwater park of the Great Barrier Reef.
The Great Barrier Reef has the largest variety of corals on the planet (up to 500 species). The threat, in addition to pollution of coastal waters and poaching, is the polyp-eating starfish crown of thorns. Rising ocean temperatures due to global warming are causing coral bleaching and death.
The main feature of the animal and plant world of Australia is the predominance of endemics. Australia is the most deserted continent. Global, depletion of water resources, depletion of flora and fauna pose a threat to the nature of the mainland. Specially protected natural areas occupy 11% of the continent's area.
Australia is often referred to as the desert continent. About 44% of the mainland's surface is occupied by desert and arid territories.
They are common on the Western Australian Plateau and on the plains of Central Australia.
In the driest regions of the center of the mainland, large areas are stony placers or shifting sands.
On the Western Australian Plateau, rocky deserts form on thick ferruginous crusts (a legacy of wet epochs). Their bare surface has a characteristic bright orange color.
On the Nullarbor Plain, composed of fissured limestones, the desert goes to the southern coast of the mainland.
Great Victoria Desert
The largest desert on the Australian continent.
Its size is about 424,400 km2.
The desert was first crossed by European explorer Ernest Giles in 1875 and named after Queen Victoria.
The average annual rainfall varies from 200 to 250 mm of rain. Thunderstorms are frequent (15-20 per year).
Daytime temperature in summer is 32-40 °C, in winter 18-23 °C.
It is generally accepted that the desert is an endless sand dunes or lifeless rocky plains. However, the Great Victoria Desert looks different. Huge variety of shrubs and small plants. After a rare rain, wild flowers and acacias contrasting on the red sand are an unforgettable sight.
Even without rain, the caves, rocks and gorges of the desert are mesmerizing.
Great Sandy Desert
The second largest after Victoria. The desert is located in the north of Western Australia, in the Kimberley region, east of the Pilbara. A small part of it lies in the Northern Territory.
The desert has an area of 360,000 km²
The Great Sandy Desert is the hottest region in Australia.
In the summer period from December to February, the average temperature reaches 35 ° C, in winter - up to 20 -15 ° C.
It is here that the famous Kata Tjuta National Park - Uluru (Ayers Rock) is located, which attracts travelers from all over the world.
Tanami
The rocky and sandy desert is located northwest of the city of Alice Springs, in the Northern Territory of Australia.
The average annual rainfall in this area is more than 400 mm, that is, there are quite a lot of rainy days for the desert. But the location of Tanami is such that high temperature prevails, and with it a high rate of evaporation.
The average daily temperature in the summer months (October-March) is around 38°C, at night 22°C. Temperature in winter: daytime - about 25 °C, night - below 10 °C.
The main landforms are dunes and sandy plains, as well as shallow water basins of the Lander River, in which there are water pits, drying marshes and salt lakes.
There is gold mining in the desert. Tourism has developed in recent years.
Gibson Desert
Sandy desert in the center of Western Australia. It borders the Great Sandy Desert to the north and the Great Victoria Desert to the south.
One of the first explorers of the region described it as "a huge hilly desert of gravel."
Soils are sandy, rich in iron, strongly weathered. In places there are thickets of veinless acacia, quinoa and spinifex grass, which bloom with bright flowers after rare rains.
Annual rainfall in the Gibson Desert can range from 200 to 250 millimeters. The climate is typically hot, in the south temperatures in summer can rise above 40°C, in winter the maximum is around 18°C and the minimum is 6°C.
Desert Simpson
The Simpson Desert is the main part of the Uluru-Kata Tjuta National Park in Australia.
This desert is famous for the fact that its sands are bright red and like scarlet waves continuously roll over the desert.
The landscapes of this place amaze the imagination: between high dunes there are areas of smooth clay crust and rocky plains strewn with turned stones. Simpson is the driest desert
The average temperature in summer (January) is 28-30 °С, in winter - 12-15 °С. In the northern part of the precipitation is less than 130 mm.
Small Sandy Desert
The Little Sandy Desert is a piece of land in Western Australia, located south of the Great Sandy Desert, and in the east it merges into the Gibson Desert.
There are several lakes in the territory of the Little Sandy Desert, the largest of which is Lake Disapointment, and it is located in the north. Seyviori is the main river that runs through this area. It flows into Lake Disapointet.
The area of the region is 101 thousand km². The average annual precipitation, which falls mainly in the summer, is 150-200 mm.
Average summer temperatures range from 22 to 38.3° C, in winter this figure is 5.4-21.3° C
Tirari Desert
It occupies an area of 15 thousand square kilometers, and it is located in the eastern part of South Australia.
The desert contains salt lakes and large dunes of sand. There are quite severe conditions, high temperatures and very little precipitation, the average annual amount of which does not exceed 125 millimeters.
It is also part of the rocky ecoregion of Australia.
The Pinnacles
A small desert in the southwest of Western Australia. The name of the desert is translated as "desert of pointed rocks". The desert got its name for towering 1-5 meters of free-standing stones in the middle of a sandy plain. The nearest settlement is the city of Cervantes, from which it is a 20-minute drive to the desert. Stones are rocks or peaks.
The Pinnacles is part of the Nambung National Park.
The landscapes in this part are exceptional, you might think that you are on another planet.
If you are a visitor to the Nambung National Park, do not miss the opportunity to see the beautiful nature of the Te Pinnacles desert.
It does not have a single sea, there are not even large stable lakes and rivers. The zones of central and western Australia are especially deserted. Here, no more than 250 mm of water reaches the surface of the earth in a year, yet the prevailing part of the deserts is covered with vegetation. The predominant plant species are triode and acacia cereals. Sometimes these areas are used for grazing livestock. However, the animals require very large territories, because. the vegetation is sparse and not very nutritious.
The flora of the deserts of Australia is quite diverse, only more than 2 thousand species of endemics are found here. Eucalyptus trees are very diverse and frequent. In places with a lot of food, you can meet animals. The largest is the kangaroo. In general, marsupials are characteristic of Australia. Marsupial shrews, moles, badgers, martens, etc. live in the desert. Many deserts are completely "dressed" with sand dunes, although they are also fixed by sparse vegetation. Only rocky deserts are practically lifeless. Moving sand dunes are very rare.
Rivers and lakes are filled with water occasionally - during rare rains. The largest lake Air, located in the desert. It is replenished with water very rarely, even in the rainy season the water of the screams (temporary rivers) does not always reach it. big desert Victoria a rather harsh place, but nevertheless it became native to some tribes (Kogara, Mirning). There is no economic activity in the desert. Maybe that's why they set up a biosphere reserve here. The Simpson Desert is quite arid, although it has a number of salt lakes. In addition, it is rich in artesian waters, but they do not contribute to the development of vegetation. The surface of the desert is sandy ridges interspersed with stony-gravel plains.
Great Sandy Desert
An area of 360 thousand square meters. km is located in the northwestern part of the continent, and is extended by a wide strip (over 1300 km) from the coast of the Indian Ocean to the McDonnell Ranges. The surface of the desert is elevated above sea level to a height of 500-700 m. A typical form of relief is latitudinal sand ridges. The amount of precipitation in the desert varies from 250 mm in the south to 400 mm in the north. There are no permanent streams, although there are many other dry channels along the periphery of the desert.
Great Australian Desert
Aboriginal people who moved to Australia 50 thousand years ago are directly responsible for the fact that most of the country's territory has turned into a desert. According to CNN , recent studies conducted by scientists from the Green Continent and the United States showed that the cause of the natural disaster that destroyed most of the flora in the country could be bonfires lit by natives. "The fire-making methods of the ancient inhabitants of Australia could lead to consequences that changed the country's climate and landscape," says Gifford MILLER from the University of Colorado USA ( Gifford Miller).
Geological studies have shown that 125,000 years ago the climate of Australia was much wetter than it is today. The fires caused by the fires of the natives could drastically reduce the area of forests, thus changing the concentration of water vapor in the atmosphere. It became insufficient for the formation of clouds, and the climate became more arid. Similar assumptions are also confirmed by computer modeling of variants of changes in climatic conditions on the continent. Paleontologists also argue that the animals that inhabited most of Australia in antiquity were better adapted to life in forests, rather than in deserts and semi-deserts. Scientists believe that it is man who is to blame for the fact that by the arrival of Europeans in Australia, 85 percent of the varieties of large animals, such as eight-meter-long lizards and car-sized turtles, had died out.
At the moment, deserts, some of which are completely devoid of any vegetation, cover more than half of the territory of Australia. A significant part of the Australian deserts, namely those that occupied the western part of the continent, are located on some elevation - on a huge plateau about 200 meters high above sea level. Some deserts rise even higher, up to 600 meters. In Australia, there are several large sand and pebble deserts, there are deserts and pure sand, but most are covered with rubble and pebbles. All the deserts of Australia are in approximately equal weather conditions - there is very little precipitation here, on average 130-160 millimeters per year. The temperature is positive all year round - in January it is about +30 Celsius, in July it is not less than +10.
Great Victoria Desert
The climatic conditions of Australia are determined by its geographical location, orographic features, the vast Pacific Ocean and the proximity of the Asian mainland. Of the three climatic zones of the southern hemisphere, the deserts of Australia are located in two: tropical and subtropical, with most of them occupied by the latter zone. In the tropical climatic zone, which occupies the territory between the 20th and 30th parallels in the desert zone, a tropical continental desert climate is formed.
The subtropical continental climate is common in the southern part of Australia, adjacent to the Great Australian Bight. These are the outskirts of the Great Victoria Desert. Therefore, in summer, from December to February, average temperatures reach 30°С, and sometimes even higher, and in winter (July-August) they decrease to an average of 15-18°С. In some years, during the entire summer period, temperatures can reach 40 ° C, and winter nights in the neighborhood of the tropics drop to 0 ° C and below. The amount and territorial distribution of precipitation is determined by the direction and nature of the winds. The main source of moisture is the "dry" southeast trade winds, since most of the moisture is retained by the mountain ranges of Eastern Australia.
The central and western parts of the country, corresponding to about half of the area, receive an average of about 250-300 mm of precipitation per year. The Simpson Desert receives the least amount of precipitation, from 100 to 150 mm per year. The rainy season in the northern half of the continent, where the monsoon change of winds dominates, is confined to the summer period, and, in its southern part, arid conditions prevail during this period. It should be noted that the amount of winter precipitation in the southern half decreases as one moves inland, rarely reaching 28°S. In turn, summer precipitation in the northern half, having the same tendency, does not spread south of the tropic. Thus, in the zone between the tropic and 28°S. there is a dry zone.
Australia is characterized by excessive variability in average annual precipitation and uneven precipitation throughout the year. The presence of long dry periods and high average annual temperatures prevailing over a large part of the continent cause high annual evaporation rates. In the central part of the mainland, they are 2000-2200 mm, decreasing towards its marginal parts. The surface waters of the mainland are extremely poor and extremely unevenly distributed over the territory. This is especially true for the desert western and central regions of Australia, which are practically drainless, but make up 50% of the continent's area. The hydrographic network of Australia is represented by temporary drying watercourses (creeks). The drainage of the rivers of the deserts of Australia belongs partly to the basin of the Indian Ocean and the basin of Lake Eyre.
The hydrographic network of the mainland is supplemented by lakes, of which there are about 800, and a significant part of them are located in deserts. The largest lakes - Eyre, Torrens, Carnegie and others - are salt marshes or dried-up basins covered with a powerful layer of salts. The lack of surface water is compensated by the richness of groundwater. A number of large artesian basins stand out here (Desert Artesian Basin, Northwest Basin, Northern Murray River Basin and part of Australia's largest groundwater basin, the Great Artesian Basin).
The soil cover of deserts is very peculiar. In the northern and central regions, red, red-brown and brown soils are distinguished (characteristic features of these soils are an acid reaction, coloring with iron oxides). Serozem-like soils are widespread in the southern parts of Australia. In western Australia, desert soils are found along the outskirts of drainless basins. The Great Sandy Desert and the Great Victoria Desert are characterized by red sandy desert soils. Salt marshes and solonetzes are widely developed in drainless internal depressions in southwestern Australia and in the basin of Lake Eyre.
The Australian deserts are divided into many different types in terms of landscape, among which Australian scientists most often distinguish mountainous and foothill deserts, structural plains deserts, rocky deserts, sandy deserts, clay deserts, plains. Sandy deserts are the most common, occupying about 32% of the continent's area. Along with sandy deserts, rocky deserts are also widespread (they occupy about 13% of the area of arid territories.
Piedmont plains are an alternation of large-stony deserts with dry channels of small rivers. This type of desert is the source of most of the country's desert streams and has always served as a habitat for the aborigines. Deserts of structural plains are found in the form of a plateau with a height of no more than 600 m above sea level. After sandy deserts, they are the most developed, occupying 23% of the area of arid territories confined mainly to Western Australia.
Australian desert flora
All the deserts of Australia lie within the Central Australian region of the Australian floral kingdom. Although, in terms of species richness and level of endemism, the desert flora of Australia is significantly inferior to the flora of the western and northeastern regions of this continent, however, compared with other desert regions of the globe, it stands out both in the number of species (more than 2 thousand) and the abundance of endemics.
Species endemism here reaches 90%: it has 85 endemic genera, of which 20 are in the Asteraceae family, 15 are haze and 12 are cruciferous. Among the endemic genera there are also background desert grasses - Mitchell's grass and triodia. A large number of species are represented by the families of legumes, myrtle, protea and Compositae. Significant species diversity is demonstrated by the genera eucalyptus, acacia, protea - Grevillea and Hakeya.
In the very center of the mainland, in the gorge of the McDonnell Desert Mountains, narrow-range endemics have been preserved: low-growing liviston palm and macrosamia from cycads. Even some types of orchids settle in the deserts - ephemera, germinating and blooming only in a short period after the rains. Sundews also penetrate here. The depressions between the ridges and the lower part of the slopes of the ridges are overgrown with clumps of prickly grass triodia.
The upper part of the slopes and the crests of the dune ridges are almost completely devoid of vegetation, only individual kurtiles of the prickly grass Zygochloi settle on loose sand. In interdune depressions and on flat sandy plains, a sparse stand of casuarina, individual specimens of eucalyptus, and veinless acacia is formed. The dwarf shrub layer is formed by Proteaceae - these are Hakeya and several types of Grevillea. Saltwort, ragodia and euhylena appear in depressions in slightly saline places.
After the rains, the depressions between the ridges and the lower parts of the slopes are covered with colorful ephemera and ephemeroids. In the northern regions on the sands in the Simpson Desert and Bolshoy Peschanoy, the species composition of background grasses changes somewhat: other types of triodia, plectrachne and shuttle beard dominate there; becomes the diversity and species composition of acacias and other shrubs. Along the channels of temporary waters they form gallery forests of several species of large eucalyptus trees. The eastern fringes of the Great Victoria Desert are occupied by sclerophyllous shrubbery of scrub mom. In the south-west of the Great Victoria Desert dominated by undersized.
Ayers Rock
Ayers Rock is the oldest and largest monolithic rock on earth (its age is approximately 500 million years), rising in the middle of a flat red desert. Tourists and photographers from all over the world flock here to admire the fantastic change of colors at sunrise and sunset, when the rock passes through all shades from brown-brown to intense glowing red, to gradually “cool down”, turn into a black silhouette with sunset. Ayers Rock was and remains a sacred rock of the Aboriginal people, and many rock paintings have survived at its foot. Excursions to Northern Territory gems such as Mount Olgas (Mt. Olgas/Kata Tjuta) and Kings Canyon also depart from here.