Brassica is a genus of plants in the mustard family. The members of the genus are informally known as cruciferous vegetables, cabbages, or mustard plants. Crops from this genus are sometimes called cole crops—derived from the Latin caulis, denoting the stem or stalk of a plant; the genus Brassica is known for its important agricultural and horticultural crops and includes a number of weeds, both of wild taxa and escapees from cultivation. Brassica species and varieties used for food include broccoli, cabbage, choy sum, rutabaga and some seeds used in the production of canola oil and the condiment mustard. Over 30 wild species and hybrids are in cultivation, plus numerous cultivars and hybrids of cultivated origin. Most are seasonal plants. Brassica plants have been the subject of much scientific interest for their agricultural importance. Six particular species evolved by the combining of chromosomes from three earlier species, as described by the Triangle of U theory; the genus is native to the Mediterranean and temperate regions of Asia.
Many wild species grow as weeds in North America, South America, Australia. A dislike for cabbage or broccoli can result from the fact that these plants contain a compound similar to phenylthiocarbamide, either bitter or tasteless to people depending on their taste buds. All parts of some species or other have been developed for food, including the root, leaves, flowers and seeds; some forms with white or purple foliage or flowerheads are sometimes grown for ornament. Brassica species are sometimes used as food plants by the larvae of a number of Lepidoptera species—see List of Lepidoptera that feed on Brassica. Brassica vegetables are regarded for their nutritional value, they provide high amounts of vitamin C and soluble fiber and contain nutrients with anticancer properties: 3,3'-diindolylmethane and selenium. Boiling reduces the level of anticancer compounds, but steaming and stir frying do not result in significant loss. Steaming these vegetable for three to four minutes is recommended to maximize sulforaphane.
Brassica vegetables are rich in indole-3-carbinol, a chemical which boosts DNA repair in cells in vitro and appears to block the growth of cancer cells in vitro. They are a good source of carotenoids, with broccoli having high levels. Researchers at the University of California at Berkeley have discovered that 3,3'-diindolylmethane in Brassica vegetables is a potent modulator of the innate immune response system with potent antiviral and anticancer activity. However, it is an antiandrogen but is known to be antiandrogenic only in hormone-sensitive prostate cancer cells; these vegetables contain goitrogens, some of which suppress thyroid function. Goitrogens can induce goiter in the absence of normal iodine intake. There is some disagreement among botanists on the classification and status of Brassica species and subspecies; the following is an abbreviated list, with an emphasis on economically important species. B. balearica: Mallorca cabbage B. carinata: Abyssinian mustard or Abyssinian cabbage, used to produce biodiesel B. elongata: elongated mustard B. fruticulosa: Mediterranean cabbage B. hilarionis: St Hilarion cabbage B. juncea: Indian mustard and leaf mustards, Sarepta mustard B. napus: rapeseed, rutabaga, Siberian kale B. narinosa: broadbeaked mustard B. nigra: black mustard B. oleracea: kale, collard greens, cauliflower, kai-lan, Brussels sprouts, kohlrabi B. perviridis: tender green, mustard spinach B. rapa: Chinese cabbage, rapini, komatsuna B. rupestris: brown mustard B. tournefortii: Asian mustard B. alba or B. hirta —see Sinapis alba B. geniculata —see Hirschfeldia incana B. kaber —see Sinapis arvensis Bayer CropScience announced it had sequenced the entire genome of rapeseed and its constituent genomes present in B. rapa and B. oleracea in 2009.
The B. rapa genome was sequenced by the Multinational Brassica Genome Project in 2011. This represents the A genome component of the amphidiploid crop species B. napus and B. juncea. ‘Brassica’ is Pliny's name for several cabbage-like plants. Media related to Brassica at Wikimedia Commons Data related to Brassica at Wikispecies
Molecular biology is a branch of biology that concerns the molecular basis of biological activity between biomolecules in the various systems of a cell, including the interactions between DNA, RNA, proteins and their biosynthesis, as well as the regulation of these interactions. Writing in Nature in 1961, William Astbury described molecular biology as:...not so much a technique as an approach, an approach from the viewpoint of the so-called basic sciences with the leading idea of searching below the large-scale manifestations of classical biology for the corresponding molecular plan. It is concerned with the forms of biological molecules and is predominantly three-dimensional and structural – which does not mean, that it is a refinement of morphology, it must at the same time inquire into function. Researchers in molecular biology use specific techniques native to molecular biology but combine these with techniques and ideas from genetics and biochemistry. There is not a defined line between these disciplines.
This is shown in the following schematic that depicts one possible view of the relationships between the fields: Biochemistry is the study of the chemical substances and vital processes occurring in live organisms. Biochemists focus on the role and structure of biomolecules; the study of the chemistry behind biological processes and the synthesis of biologically active molecules are examples of biochemistry. Genetics is the study of the effect of genetic differences in organisms; this can be inferred by the absence of a normal component. The study of "mutants" – organisms which lack one or more functional components with respect to the so-called "wild type" or normal phenotype. Genetic interactions can confound simple interpretations of such "knockout" studies. Molecular biology is the study of molecular underpinnings of the processes of replication, transcription and cell function; the central dogma of molecular biology where genetic material is transcribed into RNA and translated into protein, despite being oversimplified, still provides a good starting point for understanding the field.
The picture has been revised in light of emerging novel roles for RNA. Much of molecular biology is quantitative, much work has been done at its interface with computer science in bioinformatics and computational biology. In the early 2000s, the study of gene structure and function, molecular genetics, has been among the most prominent sub-fields of molecular biology. Many other areas of biology focus on molecules, either directly studying interactions in their own right such as in cell biology and developmental biology, or indirectly, where molecular techniques are used to infer historical attributes of populations or species, as in fields in evolutionary biology such as population genetics and phylogenetics. There is a long tradition of studying biomolecules "from the ground up" in biophysics. One of the most basic techniques of molecular biology to study protein function is molecular cloning. In this technique, DNA coding for a protein of interest is cloned using polymerase chain reaction, and/or restriction enzymes into a plasmid.
A vector has 3 distinctive features: an origin of replication, a multiple cloning site, a selective marker antibiotic resistance. Located upstream of the multiple cloning site are the promoter regions and the transcription start site which regulate the expression of cloned gene; this plasmid can be inserted into either bacterial or animal cells. Introducing DNA into bacterial cells can be done by transformation via uptake of naked DNA, conjugation via cell-cell contact or by transduction via viral vector. Introducing DNA into eukaryotic cells, such as animal cells, by physical or chemical means is called transfection. Several different transfection techniques are available, such as calcium phosphate transfection, electroporation and liposome transfection; the plasmid may be integrated into the genome, resulting in a stable transfection, or may remain independent of the genome, called transient transfection. DNA coding for a protein of interest is now inside a cell, the protein can now be expressed.
A variety of systems, such as inducible promoters and specific cell-signaling factors, are available to help express the protein of interest at high levels. Large quantities of a protein can be extracted from the bacterial or eukaryotic cell; the protein can be tested for enzymatic activity under a variety of situations, the protein may be crystallized so its tertiary structure can be studied, or, in the pharmaceutical industry, the activity of new drugs against the protein can be studied. Polymerase chain reaction is an versatile technique for copying DNA. In brief, PCR allows a specific DNA sequence to be modified in predetermined ways; the reaction is powerful and under perfect conditions could amplify one DNA molecule to become 1.07 billion molecules in less than two hours. The PCR technique can be used to introduce restriction enzyme sites to ends of DNA molecules, or to mutate particular bases of DNA, the latter is a method referred to as site-directed mutagenesis. PCR can be used to determine whether a particular DNA fragment is found in a cDNA library.
PCR has many variations, like reverse transcription PCR for amplification of RNA, more quantitative PCR which allow for quantitative measurement of DNA or RNA molecules. Gel electrophoresis is one of the principal tools of molecular biology; the basic principle is that DNA, RNA, proteins can all be separated by means of an electric field and size. In agarose gel electrophoresis, DNA and RNA can be separated on th
A hypersaline lake is a landlocked body of water that contains significant concentrations of sodium chloride or other salts, with saline levels surpassing that of ocean water. Specific microbial and crustacean species thrive in these high-salinity environments that are inhospitable to most lifeforms; some of these species enter a dormant state when desiccated, some species are thought to survive for over 250 million years. The water of hypersaline lakes has great buoyancy due to its high salt content; the most saline water body in the world is the Don Juan Pond, located in the McMurdo Dry Valleys in Antarctica. Its volume is some 3,000 cubic meters, but is changing; the Don Juan Pond has a salinity level of over 44%. Its high salinity prevents the Don Juan from freezing when temperatures are below −50 °C. There are larger hypersaline water bodies, lakes in the McMurdo Dry Valleys such as Lake Vanda with salinity of over 35%, they are covered with ice in the winter. The most saline lake outside of Antarctica is Lake Assal, in Djibouti, which has a salinity of 34.8%.
The best-known hypersaline lakes are the Dead Sea and the Great Salt Lake in the state of Utah, USA. The Dead Sea, dividing Israel and the Palestinian West Bank from Jordan, is the world's deepest hypersaline lake, the Araruama Lagoon in Brazil is the world's largest; the Great Salt Lake, located in Utah, while having nearly three times the surface area of the Dead Sea, is shallower and experiences much greater fluctuations in salinity than the Dead Sea. At its lowest recorded levels, it approaches 7.7 times the salinity of ocean water, but when its levels are high, its salinity drops to only higher than the ocean. Hypersaline lakes are found on every continent in arid or semi-arid regions; the Devon Ice Cap contains two subglacial lakes. Brine pool – An area of high density brine collected in a depression on the ocean floor Halocline – Stratification of a body of water due to salinity differences Halophile List of bodies of water by salinity Salt lake
Soil salinity control
Soil salinity control relates to controlling the problem of soil salinity and reclaiming salinized agricultural land. The aim of soil salinity control is to prevent soil degradation by salination and reclaim salty soils. Soil reclamation is called soil improvement, remediation, recuperation, or amelioration; the primary man-made cause of salinization is irrigation. River water or groundwater used in irrigation contains salts, which remain behind in the soil after the water has evaporated; the primary method of controlling soil salinity is to permit 10-20% of the irrigation water to leach the soil,that will be drained and discharged through an appropriate drainage system. The salt concentration of the drainage water is 5 to 10 times higher than that of the irrigation water, thus salt export matches salt import and it will not accumulate. Salty soils are soils; the predominant salt is sodium chloride. Saline soils are therefore sodic soils but there may be sodic soils that are not saline, but alkaline.
According to a study by UN University, about 62 million hectares, representing 20% of the world's irrigated lands are affected, up from 45 million ha in the early 1990s. In the Indo-Gangetic Plain, home to over 10% of the world's population, crop yield losses for wheat, rice and cotton grown on salt-affected lands could be 40%, 45%, 48%, 63%, respectively. Salty soils are a common feature and an environmental problem in irrigated lands in arid and semi-arid regions, resulting in poor or little crop production; the problems are associated with high water tables, caused by a lack of natural subsurface drainage to the underground. Poor subsurface drainage may be caused by insufficient transport capacity of the aquifer or because water cannot exit the aquifer, for instance if the aquifer is situated in a topographical depression. Worldwide, the major factor in the development of saline soils is a lack of precipitation. Most saline soils are found in arid regions and climates of the earth; the primary cause of man-made salinization is the salt brought in with irrigation water.
All irrigation water derived from rivers or groundwater, however'sweet', contains salts that remain behind in the soil after the water has evaporated. For example, assuming irrigation water with a low salt concentration of 0.3 g/l and a modest annual supply of irrigation water of 10,000 m³/ha brings 3,000 kg salt/ha each year. In the absence of sufficient natural drainage and without a proper leaching and drainage program to remove salts, this would lead to a high soil salinity and reduced crop yields in the long run. Much of the water used in irrigation has a higher salt content than in this example, compounded by the fact that many irrigation projects use a far greater annual supply of water. Sugar cane, for example, needs about 20,000 m3/ha of water per year; as a result, irrigated areas receive more than 3,000 kg/ha of salt per year and some receive as much as 10,000 kg/ha/year. The secondary cause of salinization is waterlogging in irrigated land. Irrigation causes changes to the natural water balance of irrigated lands.
Large quantities of water in irrigation projects must go somewhere. In irrigation projects it is impossible to achieve 100% irrigation efficiency where all the irrigation water is consumed by the plants; the maximum attainable irrigation efficiency is about 70% but it is less than 60%. This means that minimum 30%, but more than 40% of the irrigation water is not evaporated and it must go somewhere. Most of the water lost this way is stored underground which can change the original hydrology of local aquifers considerably. Many aquifers cannot absorb and transport these quantities of water and so the water table rises leading to water logging. Waterlogging causes three problems: The shallow water table and lack of oxygenation of the root zone reduces the yield of most crops It leads to an accumulation of salts brought in with the irrigation water as their removal through the aquifer is blocked With the upward seepage of groundwater more salts are brought into the soil and the salination is aggravatedAquifer conditions in irrigated land and the groundwater flow have an important role in soil salinization, as illustrated here: Illustration of the influence of aquifer conditions on soil salinization in irrigated land Normally, the salinization of agricultural land affects a considerable area of irrigation projects, on the order of 20 to 30%.
When the agriculture in such a fraction of the land is abandoned, a new salt and water balance is attained, a new equilibrium is reached, the situation becomes stable. In India alone, thousands of square kilometres have been salinized. China and Pakistan do not lag much behind. A regional distribution of the 3,230,000 km² of saline land worldwide is shown in the following table derived from the FAO/UNESCO Soil Map of the World. Although the principles of the processes of salinization are easy to understand, it is more difficult to explain why certain parts of the land suffer from the problems and other parts do not, or to predict which part of the land will fall victim; the main reason for this is the variation of natural conditions in time and space, the uneven distribution of the irrigation water, the seasonal or yearly changes of agricultural practices. Only in lands with undulating topography is the prediction simple: the depressiona
Dryland farming and dry farming encompass specific agricultural techniques for the non-irrigated cultivation of crops. Dryland farming is associated with drylands, areas characterized by a cool wet season, followed by a warm dry season, they are associated with arid conditions or areas prone to drought or having scarce water resources. Additionally, arid-zone agriculture is being developed for this purpose. Dryland farming is used in the Great Plains, the Palouse plateau of Eastern Washington, other arid regions of North America such as in the Southwestern United States and Mexico, the Middle East and in other grain growing regions such as the steppes of Eurasia and Argentina. Dryland farming was introduced to southern Russia and Ukraine by Ukrainian Mennonites under the influence of Johann Cornies, making the region the breadbasket of Europe. In Australia, it is practiced in all states but the Northern Territory. Dryland farmed crops may include winter wheat, beans, sunflowers or watermelon.
Successful dryland farming is possible with as little as 230 millimetres of precipitation a year. Native American tribes in the arid Southwest survived for hundreds of years on dryland farming in areas with less than 250 millimetres of rain; the choice of crop is influenced by the timing of the predominant rainfall in relation to the seasons. For example, winter wheat is more suited to regions with higher winter rainfall while areas with summer wet seasons may be more suited to summer growing crops such as sorghum, sunflowers or cotton. Dryland farming has evolved as a set of techniques and management practices used by farmers to continually adapt to the presence or lack of moisture in a given crop cycle. In marginal regions, a farmer should be financially able to survive occasional crop failures for several years in succession. Survival as a dryland farmer requires careful husbandry of the moisture available for the crop and aggressive management of expenses to minimize losses in poor years.
Dryland farming involves the constant assessing of the amount of moisture present or lacking for any given crop cycle and planning accordingly. Dryland farmers know that to be financially successful they have to be aggressive during the good years in order to offset the dry years. Dryland farming is dependent on natural rainfall, which can leave the ground vulnerable to dust storms if poor farming techniques are used or if the storms strike at a vulnerable time; the fact that a fallow period must be included in the crop rotation means that fields cannot always be protected by a cover crop, which might otherwise offer protection against erosion. Some of the theories of dryland farming developed in the late 19th and early 20th centuries claimed to be scientific but were in reality pseudoscientific and did not stand up to empirical testing. For example, it was alleged that tillage would seal in moisture, but such "dust mulching" ideas are based on what people imagine should happen, or have been told, rather than what testing confirms.
The book Bad Land: An American Romance explores the effects that this had on people who were encouraged to homestead in an area with little rainfall. Capturing and conservation of moisture – In regions such as Eastern Washington, the average annual precipitation available to a dryland farm may be as little as 220 millimetres. Moisture must be captured until the crop can utilize it. Techniques include summer fallow rotation, preventing runoff by terracing fields. "Terracing" is practiced by farmers on a smaller scale by laying out the direction of furrows to slow water runoff downhill by plowing along either contours or keylines. Moisture can be conserved by leaving crop residue to shade the soil. Effective use of available moisture – Once moisture is available for the crop to use, it must be used as as possible. Seed planting depth and timing are considered to place the seed at a depth at which sufficient moisture exists, or where it will exist when seasonal precipitation falls. Farmers tend to use crop varieties which are heat-stress tolerant.
Thus the likelihood of a successful crop is hedged. Soil conservation – The nature of dryland farming makes it susceptible to erosion wind erosion; some techniques for conserving soil moisture are at odds with techniques for conserving topsoil. Since healthy topsoil is critical to sustainable dryland agriculture, its preservation is considered the most important long-term goal of a dryland farming operation. Erosion control techniques such as windbreaks, reduced tillage or no-till, spreading straw, strip farming are used to minimize topsoil loss. Control of input costs – Dryland farming is practiced in regions inherently marginal for non-irrigated agriculture; because of this, there is an increased risk of crop failure and poor yields which may occur in a dry year. Dryland farmers must evaluate the potential yield of a crop throughout the growing season and be prepared to decrease inputs to the crop such as fertilizer and weed control if it appears that it is to have a poor yield due to insufficient moisture.
Conversely, in years when moisture is abundant, farmers may increase their inpu
Botswana the Republic of Botswana, is a landlocked country in Southern Africa. The British protectorate of Bechuanaland, Botswana adopted its new name after becoming independent within the Commonwealth on 30 September 1966. Since it has maintained a tradition of stable representative republic, with a consistent record of uninterrupted democratic elections and the best perceived corruption ranking in Africa since at least 1998, it is Africa's oldest continuous democracy. Botswana is topographically flat, with up to 70 percent of its territory being the Kalahari Desert, it is bordered by South Africa to the south and southeast, Namibia to the west and north, Zimbabwe to the northeast. Its border with Zambia to the north near Kazungula is poorly defined but is, at most, a few hundred metres long. A mid-sized country of just over 2 million people, Botswana is one of the most sparsely populated countries in the world. Around 10 percent of the population lives in the capital and largest city, Gaborone.
One of the poorest countries in the world—with a GDP per capita of about US$70 per year in the late 1960s—Botswana has since transformed itself into one of the world's fastest-growing economies. The economy is dominated by mining and tourism. Botswana boasts a GDP per capita of about $18,825 per year as of 2015, one of the highest in Africa, its high gross national income gives the country a high standard of living and the highest Human Development Index of continental Sub-Saharan Africa. Botswana is a member of the African Union, the Southern African Development Community, the Commonwealth of Nations, the United Nations; the country has been among the hardest hit by the HIV/AIDS epidemic. Despite the success in programmes to make treatments available to those infected, to educate the populace in general about how to stop the spread of HIV/AIDS, the number of people with AIDS rose from 290,000 in 2005 to 320,000 in 2013; as of 2014, Botswana has the third-highest prevalence rate for HIV/AIDS, with 20% of the population infected.
The country's name means "land of the tswana", referring to the dominant ethnic group in Botswana. The term Batswana was applied to the Tswana, still the case. However, it has come to be used as a demonym for all citizens of Botswana. Many English dictionaries recommend the term Botswanan to refer to people of Botswana. Archaeological digs have shown. Stone tools and fauna remains have shown that all areas of the country were inhabited at least 400,000 years ago. Evidence left by modern humans such as cave paintings are about 73,000 years old; the original inhabitants of southern Africa were the Khoi peoples. Both speak Khoisan languages and hunted and traded over long distances; when cattle were first introduced about 2000 years ago into southern Africa, pastoralism became a major feature of the economy, since the region had large grasslands free of tsetse fly. It is unclear when Bantu-speaking peoples first moved into the country from the north, although AD 600 seems to be a consensus estimate.
In that era, the ancestors of the modern-day Kalanga moved into what is now the north-eastern areas of the country. These proto-Kalanga were connected to states in Zimbabwe as well as to the Mapungubwe state; these states, located outside of current Botswana's borders, appear to have kept massive cattle herds in what is now the Central District—apparently at numbers approaching modern cattle density. This massive cattle-raising complex prospered until 1300 AD or so, seems to have regressed following the collapse of Mapungubwe. During this era, the first Tswana-speaking groups, the Bakgalagadi, moved into the southern areas of the Kalahari. All these various peoples were connected to trade routes that ran via the Limpopo River to the Indian Ocean, trade goods from Asia such as beads made their way to Botswana most in exchange for ivory and rhinoceros horn; the arrival of the ancestors of the Tswana-speakers who came to control the region has yet to be dated precisely. Members of the Bakwena, a chieftaincy under a legendary leader named Kgabo II, made their way into the southern Kalahari by AD 1500, at the latest, his people drove the Bakgalagadi inhabitants west into the desert.
Over the years, several offshoots of the Bakwena moved into adjoining territories. The Bangwaketse occupied areas to the west, while the Bangwato moved northeast into Kalanga areas. Not long afterwards, a Bangwato offshoot known as the Batawana migrated into the Okavango Delta in the 1790s; the first written records relating to modern-day Botswana appear in 1824. What these records show is that the Bangwaketse had become the predominant power in the region. Under the rule of Makaba II, the Bangwaketse kept vast herds of cattle in well-protected desert areas, used their military prowess to raid their neighbors. Other chiefdoms in the area, by this time, had capitals of 10,000 or so and were prosperous; this equilibrium came to end during the Mfecane period, 1823–1843, when a succession of invading peoples from South Africa entered the country. Although the Bangwaketse were able to defeat the invading Bakololo in 1826, over time all the major chiefdoms in Botswana were attacked and impoverished.
The Bakololo and Amandebele raided and took large numbers of cattle and children from the Batswana—most of whom were driven into the desert or sanctuary areas such as hilltops and caves. Only after 1843, when the Amandebele moved into western Zimbabwe, did this threat subside. During th
The Makgadikgadi Pan, a salt pan situated in the middle of the dry savanna of north-eastern Botswana, is one of the largest salt flats in the world. The pan is all that remains of the enormous Lake Makgadikgadi, which once covered an area larger than Switzerland, but dried up several thousand years ago; the name Makgadikgadi is derived from the same root as the name for the desert Kalahari, meaning a dry thirsty place in the languages of the San people. Lying southeast of the Okavango Delta and surrounded by the Kalahari Desert, Makgadikgadi is technically not a single pan, but many pans with sandy desert in between, the largest being the Sua and Nxai Pans; the largest individual pan is about 1,900 sq mi. In comparison, Salar de Uyuni in Bolivia is a single salt flat of 4,100 sq mi has much water, is claimed to be the world's largest salt pan. A dry, clay crust most of the year, the pans are seasonally covered with water and grass, are a refuge for birds and animals in this arid part of the world.
The climate with regular annual rains. The main water source is the Nata River, called Amanzanyama in Zimbabwe, where it rises at Sandown about 37 mi from Bulawayo. A smaller amount of water is supplied by the Boteti River from the Okavango Delta; these salt pans cover 6,200 sq mi in the Kalahari Basin and form the bed of the ancient Lake Makgadikgadi, which evaporated many millennia ago. Archaeological recovery in the Makgadikgadi Pan has revealed the presence of prehistoric man through abundant finds of stone tools. Pastoralists herded grazing livestock here; the lowest place in the basin is Sua Pan with an elevation of 2,920 feet. As the ancestral Lake Makgadikgadi shrank, it left relict shorelines, which are most evident in the southwestern part of the basin; as the lake shrank numerous smaller lakes formed with progressively smaller shorelines. The relict shorelines at elevations of 3100 feet and 3018 feet can be seen easily on Gidikwe Ridge, west of the Boteti River; the geologic processes behind the formation of the basin are not well understood.
It is conjectured that there was a gentle down-warping of the crust, with accompanying mild tectonics and associated faulting. The main axis of the developing graben runs northeast-southwest. Kubu Island and Kukome Island are igneous rock "islands" in the salt flat of Sua pan. Kubu Island lies in the southwestern quadrant of Sua Pan, contains a number of baobab trees, is protected as a national monument; the pans themselves are salty desert. However the fringes of the pan are salt marshes and further out these are circled by grassland and shrubby savanna; the prominent baobab trees found in the area function as local landmarks. One of them, named after James Chapman, served as an unofficial post office for 19th-century explorers. Little wildlife can exist here during the harsh dry season of strong hot winds and only salt water, but following a rain the pan becomes an important habitat for migrating animals including wildebeest and one of Africa's biggest zebra populations, the large predators that prey on them.
The wet season brings migratory birds such as ducks and great white pelicans. The pan is home of one of only two breeding populations of greater flamingos in southern Africa, only on the Soa pan, part of the Makgadikgadi pans; the other breeding population is in the Northern part of Namibia. The only birds here in the dry season are chestnut-banded plover and Kittlitz's plover; the grasslands on the fringes of the pan are home to reptiles such as tortoises, rock monitor and lizards including the endemic Makgadikgadi spiny agama. The region's salt water is home to the cladoceran crustacean Moina belli; the salt pans are inhospitable and human intervention has been minimal so they remain undisturbed, although land surrounding the pans is used for grazing and some areas have been fenced off, preventing the migration of wildlife. Modern commercial operations to extract salt and soda ash began on Sua Pan in 1991, there are plans to divert water from the Nata River for irrigation, which would cause severe damage to the salt pan ecosystem.
Another threat is the use of quad bikes and off-road vehicles by tourists, which disturbs breeding colonies of flamingos. Illegal hunting in the national parks is a persistent problem. There are some protected areas within Nxai Pan National Park; the Makgadikgadi Pans Game Reserve is the scene of large migrations of zebra and wildebeest from the Boteti River across to Nwetwe Pan, while the Nata Sanctuary in Sua Pan is a place to see birdlife and antelopes. In Nxai Pan the baobabs painted by 19th century British artist; the area can be accessed from the town of Gweta. Daphnia barbata Lovenula africana Sigara Top Gear: Botswana Special Images from the Mkgadikgadi Pans "Zambezian halophytics". Terrestrial Ecoregions. World Wildlife Fund