Desertification is a type of land degradation in which a dry area of land becomes a desert losing its bodies of water as well as vegetation and wildlife. It is caused by a variety of factors, such as through climate change and through the overexploitation of soil through human activity; when deserts appear automatically over the natural course of a planet's life cycle it can be called a natural phenomenon. Desertification is a significant global ecological and environmental problem with far reaching consequences on socio-economic and political conditions. Considerable controversy exists over the proper definition of the term "desertification" for which Helmut Geist has identified more than 100 formal definitions; the most accepted of these is that of the Princeton University Dictionary which defines it as "the process of fertile land transforming into desert as a result of deforestation, drought or improper/inappropriate agriculture". Desertification has been neatly defined in the text of the United Nations Convention to Combat Desertification as "land degradation in arid, semi-arid and dry sub-humid regions resulting from various factors, including climatic variations and human activities."Another major contribution to the controversy comes from the sub-grouping of types of desertification.
Spanning from the vague yet shortsighted view as the "man-made-desert" to the broader yet less focused type as the "Non-pattern-Desert". The earliest known discussion of the topic arose soon after the French colonization of West Africa, when the Comité d'Etudes commissioned a study on desséchement progressif to explore the prehistoric expansion of the Sahara Desert; the world's most noted deserts have been formed by natural processes interacting over long intervals of time. During most of these times, deserts have 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 core deserts, such as the Sahara, the largest hot desert. Desertification has played a significant role in human history, contributing to the collapse of several large empires, such as Carthage and the Roman Empire, as well as causing displacement of local populations. Historical evidence shows that the serious and extensive land deterioration occurring several centuries ago in arid regions had three epicenters: the Mediterranean, the Mesopotamian Valley, the Loess Plateau of China, where population was dense.
Drylands occupy 40–41% of Earth’s land area and are home to more than 2 billion people. It has been estimated that some 10–20% of drylands are degraded, the total area affected by desertification being between 6 and 12 million square kilometres, that about 1–6% of the inhabitants of drylands live in desertified areas, that a billion people are under threat from further desertification; as of 1998, the then-current degree of southward expansion of the Sahara was not well known, due to a lack of recent, measurable expansion of the desert into the Sahel at the time. The impact of global warming and human activities are presented in the Sahel. In this area, the level of desertification is high compared to other areas in the world. All areas situated in the eastern part of Africa are characterized by a dry climate, hot temperatures, low rainfall. So, droughts are the rule in the Sahel region; some studies have shown that Africa has lost 650,000 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 to the south over a stretch of land from west to east 6,000 km long; the survey, done by the research institute for development, had demonstrated that this means dryness is spreading fast in the Sahelian countries. 70% of the arid area has deteriorated and water resources have disappeared, leading to soil degradation. The loss of topsoil means that plants cannot take root and can be uprooted by torrential water or strong winds; the United Nations Convention says that about six million Sahelian citizens would have to give up the desertified zones of sub-Saharan Africa for North Africa and Europe between 1997 and 2020. Another major area, being impacted by desertification is the Gobi Desert; the Gobi desert is the fastest moving desert on Earth. This has destroyed many villages in its path. Photos show that the Gobi Desert has expanded to the point the entire nation of Croatia could fit inside its area.
This is causing a major problem for the people of China. They will soon have to deal with the desert. Although the Gobi Desert itself is still a distance away from Beijing, reports from field studies state there are large sand dunes forming only 70 km outside the city; as the desertification takes place, the landscape may progress through different stages and continuously transform in appearance. On sloped terrain, desertification can create 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. One outcome of this observation suggests an optimal plan
United Nations Framework Convention on Climate Change
The United Nations Framework Convention on Climate Change is an international environmental treaty adopted on 9 May 1992 and opened for signature at the Earth Summit in Rio de Janeiro from 3 to 14 June 1992. It entered into force on 21 March 1994, after a sufficient number of countries had ratified it; the UNFCCC objective is to "stabilize greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system". The framework sets non binding limits on greenhouse gas emissions for individual countries and contains no enforcement mechanisms. Instead, the framework outlines how specific international treaties may be negotiated to specify further action towards the objective of the UNFCCC Initially, an Intergovernmental Negotiating Committee produced the text of the Framework Convention during its meeting in New York from 30 April to 9 May 1992; the UNFCCC was adopted on 9 May 1992, opened for signature on 4 June 1992. The UNFCCC has 197 parties as of December 2015.
The convention enjoys broad legitimacy due to its nearly universal membership. The parties to the convention have met annually from 1995 in Conferences of the Parties to assess progress in dealing with climate change. In 1997, the Kyoto Protocol was concluded and established binding obligations for developed countries to reduce their greenhouse gas emissions in the period 2008–2012; the 2010 United Nations Climate Change Conference produced an agreement stating that future global warming should be limited to below 2.0 °C relative to the pre-industrial level. The Protocol was amended in 2012 to encompass the period 2013–2020 in the Doha Amendment, which as of December 2015 had not entered into force. In 2015 the Paris Agreement was adopted, governing emission reductions from 2020 on through commitments of countries in Nationally Determined Contributions, lowering the target to 1.5 °C. The Paris Agreement entered into force on 4 November 2016. One of the first tasks set by the UNFCCC was for signatory nations to establish national greenhouse gas inventories of greenhouse gas emissions and removals, which were used to create the 1990 benchmark levels for accession of Annex I countries to the Kyoto Protocol and for the commitment of those countries to GHG reductions.
Updated inventories must be submitted annually by Annex I countries. "UNFCCC" is the name of the United Nations Secretariat charged with supporting the operation of the Convention, with offices in Haus Carstanjen, the UN Campus in Bonn, Germany. From 2010 to 2016 the head of the secretariat was Christiana Figueres. In July 2016, Patricia Espinosa succeeded Figueres; the Secretariat, augmented through the parallel efforts of the Intergovernmental Panel on Climate Change, aims to gain consensus through meetings and the discussion of various strategies. The United Nations Framework Convention on Climate Change was opened for signature at the 1992 United Nations Conference on Environment and Development in Rio de Janeiro. On 12 June 1992, 154 nations signed the UNFCCC, which upon ratification committed signatories' governments to reduce atmospheric concentrations of greenhouse gases with the goal of "preventing dangerous anthropogenic interference with Earth's climate system"; this commitment would require substantial reductions in greenhouse gas emissions Article 3 of the Convention states that Parties should act to protect the climate system on the basis of "common but differentiated responsibilities", that developed country Parties should "take the lead" in addressing climate change.
Under Article 4, all Parties make general commitments to address climate change through, for example, climate change mitigation and adapting to the eventual impacts of climate change. Article 4 states: The extent to which developing country Parties will implement their commitments under the Convention will depend on the effective implementation by developed country Parties of their commitments under the Convention related to financial resources and transfer of technology and will take into account that economic and social development and poverty eradication are the first and overriding priorities of the developing country Parties; the Framework Convention specifies the aim of developed Parties stabilizing their greenhouse gas emissions at 1990 levels, by the year 2000. After the signing of the UNFCCC treaty, Parties to the UNFCCC have met at conferences to discuss how to achieve the treaty's aims. At the 1st Conference of the Parties, Parties decided that the aim of Annex I Parties stabilizing their emissions at 1990 levels by the year 2000 was "not adequate", further discussions at conferences led to the Kyoto Protocol.
The Kyoto Protocol sets emissions targets for developed countries which are binding under international law. The Kyoto Protocol has had two commitment periods, the first of which lasted from 2008-2012; the second one runs from 2013-2020 and is based on the Doha Amendment to the Protocol, which has not entered into force. The US has not ratified the Kyoto Protocol, while Canada denounced it in 2012; the Kyoto Protocol has been ratified by all the other Annex I Parties. All Annex I Parties, excluding the US, have participated in the 1st Kyoto commitment period. 37 Annex I countries and the EU have agreed to second-round Kyoto targets. These countries are Australia, all members of the European Union, Croatia, Kazakhstan, Norway, Sw
Iron ores are rocks and minerals from which metallic iron can be economically extracted. The ores are rich in iron oxides and vary in colour from dark grey, bright yellow, or deep purple to rusty red; the iron is found in the form of magnetite, goethite, limonite or siderite. Ores containing high quantities of hematite or magnetite are known as "natural ore" or "direct shipping ore", meaning they can be fed directly into iron-making blast furnaces. Iron ore is the raw material used to make pig iron, one of the main raw materials to make steel—98% of the mined iron ore is used to make steel. Indeed, it has been argued that iron ore is "more integral to the global economy than any other commodity, except oil". Metallic iron is unknown on the surface of the Earth except as iron-nickel alloys from meteorites and rare forms of deep mantle xenoliths. Although iron is the fourth most abundant element in the Earth's crust, comprising about 5%, the vast majority is bound in silicate or more carbonate minerals.
The thermodynamic barriers to separating pure iron from these minerals are formidable and energy intensive, therefore all sources of iron used by human industry exploit comparatively rarer iron oxide minerals hematite. Prior to the industrial revolution, most iron was obtained from available goethite or bog ore, for example during the American Revolution and the Napoleonic Wars. Prehistoric societies used laterite as a source of iron ore. Much of the iron ore utilized by industrialized societies has been mined from predominantly hematite deposits with grades of around 70% Fe; these deposits are referred to as "direct shipping ores" or "natural ores". Increasing iron ore demand, coupled with the depletion of high-grade hematite ores in the United States, after World War II led to development of lower-grade iron ore sources, principally the utilization of magnetite and taconite. Iron-ore mining methods vary by the type of ore being mined. There are four main types of iron-ore deposits worked depending on the mineralogy and geology of the ore deposits.
These are magnetite, massive hematite and pisolitic ironstone deposits. Banded iron formations are sedimentary rocks containing more than 15% iron composed predominantly of thinly bedded iron minerals and silica. Banded iron formations occur in Precambrian rocks, are weakly to intensely metamorphosed. Banded iron formations may contain iron in carbonates or silicates, but in those mined as iron ores, oxides are the principal iron mineral. Banded iron formations are known as taconite within North America; the mining involves moving tremendous amounts of waste. The waste comes in two forms, non-ore bedrock in the mine, unwanted minerals which are an intrinsic part of the ore rock itself; the mullock is mined and piled in waste dumps, the gangue is separated during the beneficiation process and is removed as tailings. Taconite tailings are the mineral quartz, chemically inert; this material is stored in regulated water settling ponds. The key economic parameters for magnetite ore being economic are the crystallinity of the magnetite, the grade of the iron within the banded iron formation host rock, the contaminant elements which exist within the magnetite concentrate.
The size and strip ratio of most magnetite resources is irrelevant as a banded iron formation can be hundreds of meters thick, extend hundreds of kilometers along strike, can come to more than three billion or more tonnes of contained ore. The typical grade of iron at which a magnetite-bearing banded iron formation becomes economic is 25% iron, which can yield a 33% to 40% recovery of magnetite by weight, to produce a concentrate grading in excess of 64% iron by weight; the typical magnetite iron-ore concentrate has less than 0.1% phosphorus, 3–7% silica and less than 3% aluminium. Magnetite iron ore is mined in Minnesota and Michigan in the U. S. Eastern Canada and Northern Sweden. Magnetite bearing banded iron formation is mined extensively in Brazil, which exports significant quantities to Asia, there is a nascent and large magnetite iron-ore industry in Australia. Direct-shipping iron-ore deposits are exploited on all continents except Antarctica, with the largest intensity in South America and Asia.
Most large hematite iron-ore deposits are sourced from altered banded iron formations and igneous accumulations. DSO deposits are rarer than the magnetite-bearing BIF or other rocks which form its main source or protolith rock, but are cheaper to mine and process as they require less beneficiation due to the higher iron content. However, DSO ores can contain higher concentrations of penalty elements being higher in phosphorus, water content and aluminum. Export grade DSO ores are in the 62–64% Fe range. Granite and ultrapotassic igneous rocks segregate magnetite crystals and form masses of magnetite suitable for economic concentration. A few iron ore deposits, notably in Chile, are formed from volcanic flows containing significant accumulations of magnetite phenocrysts. Chilean magnetite iron ore deposits within the Atacama Desert have formed alluvial accumulations of magnetite in s
Tropical rainforests are rainforests that occur in areas of tropical rainforest climate in which there is no dry season – all months have an average precipitation of at least 60 mm – and may be referred to as lowland equatorial evergreen rainforest. True rainforests are found between 10 degrees north and south of the equator. Within the World Wildlife Fund's biome classification, tropical rainforests are a type of tropical moist broadleaf forest that includes the more extensive seasonal tropical forests. Tropical rainforests can be characterized in two words: wet. Mean monthly temperatures exceed 18 °C during all months of the year. Average annual rainfall is no less than 1,680 mm and can exceed 10 m although it lies between 1,750 mm and 3,000 mm; this high level of precipitation results in poor soils due to leaching of soluble nutrients in the ground. Tropical rainforests exhibit high levels of biodiversity. Around 40% to 75% of all biotic species are indigenous to the rainforests. Rainforests are home to half of all the living plant species on the planet.
Two-thirds of all flowering plants can be found in rainforests. A single hectare of rainforest may contain 42,000 different species of insect, up to 807 trees of 313 species and 1,500 species of higher plants. Tropical rainforests have been called the "world's largest pharmacy", because over one quarter of natural medicines have been discovered within them, it is that there may be many millions of species of plants and microorganisms still undiscovered in tropical rainforests. Tropical rainforests are among the most threatened ecosystems globally due to large-scale fragmentation as a result of human activity. Habitat fragmentation caused by geological processes such as volcanism and climate change occurred in the past, have been identified as important drivers of speciation. However, fast human driven habitat destruction is suspected to be one of the major causes of species extinction. Tropical rain forests have been subjected to heavy logging and agricultural clearance throughout the 20th century, the area covered by rainforests around the world is shrinking.
Tropical rainforests have existed on earth for hundreds of millions of years. Most tropical rainforests today are on fragments of the Mesozoic era supercontinent of Gondwana; the separation of the landmass resulted in a great loss of amphibian diversity while at the same time the drier climate spurred the diversification of reptiles. The division left tropical rainforests located in five major regions of the world: tropical America, Southeast Asia and New Guinea, with smaller outliers in Australia. However, the specifics of the origin of rainforests remain uncertain due to an incomplete fossil record. Several biomes may appear similar-to, or merge via ecotones with, tropical rainforest: Moist seasonal tropical forest Moist seasonal tropical forests receive high overall rainfall with a warm summer wet season and a cooler winter dry season; some trees in these forests drop some or all of their leaves during the winter dry season, thus they are sometimes called "tropical mixed forest". They are found in parts of South America, in Central America and around the Caribbean, in coastal West Africa, parts of the Indian subcontinent, across much of Indochina.
Montane rainforests These are found in cooler-climate mountainous areas, becoming known as cloud forests at higher elevations. Depending on latitude, the lower limit of montane rainforests on large mountains is between 1500 and 2500 m while the upper limit is from 2400 to 3300 m. Flooded rainforests Tropical freshwater swamp forests, or "flooded forests", are found in Amazon basin and elsewhere. Rainforests are divided into different strata, or layers, with vegetation organized into a vertical pattern from the top of the soil to the canopy; each layer is a unique biotic community containing different plants and animals adapted for life in that particular strata. Only the emergent layer is unique to tropical rainforests, while the others are found in temperate rainforests; the forest floor, the bottom-most layer, receives only 2% of the sunlight. Only plants adapted to low light can grow in this region. Away from riverbanks and clearings, where dense undergrowth is found, the forest floor is clear of vegetation because of the low sunlight penetration.
This more open quality permits the easy movement of larger animals such as: ungulates like the okapi, Sumatran rhinoceros, apes like the western lowland gorilla, as well as many species of reptiles and insects. The forest floor contains decaying plant and animal matter, which disappears because the warm, humid conditions promote rapid decay. Many forms of fungi growing here help decay the plant waste; the understory layer lies between the forest floor. The understory is home to a number of birds, small mammals, insects and predators. Examples include leopard, poison dart frogs, ring-tailed coati, boa constrictor, many species of Coleoptera; the vegetation at this layer consists of shade-tolerant shrubs, small trees, large woody vines which climb into the trees to capture sunlight. Only about 5% of sunlight breaches the canopy to arrive at the understory causing true understory plants to grow to 3 m; as an
Monrovia is the capital city of the West African country of Liberia. Located on the Atlantic Coast at Cape Mesurado, Monrovia had a population of 1,010,970 as of the 2008 census. With 29% of the total population of Liberia, Monrovia is the country's most populous city. Founded on April 25, 1822, Monrovia was the second permanent Black American settlement in Africa after Freetown, Sierra Leone. Monrovia's economy is shaped by its harbour and its role as the location of Liberia's government offices. Monrovia is named in honor of U. S. President James Monroe, a prominent supporter of the colonization of Liberia and the American Colonization Society. Along with Washington, D. C. it is one of two national capitals to be named after a U. S. President. In 1816, with the aim of establishing a self-sufficient colony for emancipated American slaves, something, accomplished in Freetown, the first settlers arrived in Africa from the United States, under the auspices of the American Colonization Society, they landed at Sherbro Island in present-day Sierra Leone.
Many settlers died in the landing. On January 7, 1822, a second ship rescued the settlers and took them to Cape Mesurado, establishing the settlement of Christopolis. In 1824, the city was renamed Monrovia after James Monroe President of the United States, a prominent supporter of the colony in sending freed Black slaves and ex-Caribbean slaves from the United States of America and Caribbean islands to Liberia and who saw it as preferable to emancipation in America. In 1845, Monrovia was the site of the constitutional convention held by the American Colonization Society which drafted the constitution that would two years be the constitution of an independent and sovereign Republic of Liberia. At the beginning of the 20th century, Monrovia was divided into two parts: Monrovia proper, where the city's Americo-Liberian population resided and was reminiscent of the Southern United States in architecture. Of the 4,000 residents, 2,500 were Americo-Liberian. By 1926, ethnic groups from Liberia's interior began migrating to Monrovia in search of jobs.
In 1979, the Organisation of African Unity held their conference in the Monrovia area, with president William Tolbert as chairman. During his term, Tolbert improved public housing in Monrovia and decreased by 50% the tuition fees at the University of Liberia. A military coup led by Samuel Doe ousted the Tolbert government in 1980, with many members being executed; the city was damaged in the First and Second Liberian Civil Wars, notably during the siege of Monrovia, with many buildings damaged and nearly all the infrastructure destroyed. Major battles occurred between Samuel Doe's government and Prince Johnson's forces in 1990 and with the NPFL's assault on the city in 1992. A legacy of the war is a large population of homeless children and youths, either having been involved in the fighting or denied an education by it. In 2002, Leymah Gbowee organized the Women of Liberia Mass Action for Peace with local women praying and singing in a fish market in Monrovia; this movement helped bring an end to the Second Liberian Civil War in 2003 and the election of Ellen Johnson Sirleaf in Liberia, the first African nation with a female president.
In 2014, the city was affected by the 2014 West Africa Ebola outbreak. The Ebola virus epidemic in Liberia was declared over on 3 September 2015. Monrovia lies along the Cape Mesurado peninsula, between the Atlantic Ocean and the Mesurado River, whose mouth forms a large natural harbor; the Saint Paul River lies directly north of the city and forms the northern boundary of Bushrod Island, reached by crossing the "New Bridge" from downtown Monrovia. Monrovia is located in Montserrado County and is Liberia's largest city and its administrative and financial center. Under the Köppen climate classification, Monrovia features a tropical monsoon climate. During the course of the year Monrovia sees a copious amount of precipitation. Monrovia averages 4,624 mm of rain per year. In fact, Monrovia is the wettest capital city, receiving more annual precipitation on average, than any other capital in the world; the climate features a wet season and a dry season, but precipitation is seen during the dry season.
Temperatures remain constant throughout the year averaging around 26.4 °C. The city of Monrovia consists of several districts, spread across the Mesurado peninsula, with the greater Metropolitan area encircling the marshy Mesurado river's mouth; the historic downtown, centered on Broad Street, is at the end of the peninsula, with the major market district, Waterside to the north, facing the city's large natural harbor. Northwest of Waterside is the low-income West Point community. To the west/southwest of downtown lies Mamba Point, traditionally the city's principal diplomatic quarter, home to the Embassies of the United States and United Kingdom as well as the European Union Delegation. South of the city center is Capitol Hill, where the major institutions of national government, including the Temple of Justice and the Executive Mansion, are located. Further east down the peninsula is the Sinkor section of Monrovia. A suburban residential district, today Sinkor acts as Monrovia's bustling mid-town, hosting many diplomatic missions, as well as major hotels, businesses, as well as several residential neighborhoods, including informal communities such as Plumkor, Jorkpentown and Fiamah.
Sinkor is home to the city's secondary airport, Spriggs Payne, the area nearby, called Airfield, is a major nightlife district for the whole city. Further east of the Airfield is the Old Road section o
Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. At room temperature and pressure, another solid form of carbon known as graphite is the chemically stable form, but diamond never converts to it. Diamond has the highest hardness and thermal conductivity of any natural material, properties that are utilized in major industrial applications such as cutting and polishing tools, they are the reason that diamond anvil cells can subject materials to pressures found deep in the Earth. Because the arrangement of atoms in diamond is rigid, few types of impurity can contaminate it. Small numbers of defects or impurities color diamond blue, brown, purple, orange or red. Diamond has high optical dispersion. Most natural diamonds have ages between 1 billion and 3.5 billion years. Most were formed at depths between 150 and 250 kilometers in the Earth's mantle, although a few have come from as deep as 800 kilometers. Under high pressure and temperature, carbon-containing fluids dissolved minerals and replaced them with diamonds.
Much more they were carried to the surface in volcanic eruptions and deposited in igneous rocks known as kimberlites and lamproites. Synthetic diamonds can be grown from high-purity carbon under high pressures and temperatures or from hydrocarbon gas by chemical vapor deposition. Imitation diamonds can be made out of materials such as cubic zirconia and silicon carbide. Natural and imitation diamonds are most distinguished using optical techniques or thermal conductivity measurements. Diamond is a solid form of pure carbon with its atoms arranged in a crystal. Solid carbon comes in different forms known as allotropes depending on the type of chemical bond; the two most common allotropes of pure carbon are graphite. In graphite the bonds are sp2 orbital hybrids and the atoms form in planes with each bound to three nearest neighbors 120 degrees apart. In diamond they are sp3 and the atoms form tetrahedra with each bound to four nearest neighbors. Tetrahedra are rigid, the bonds are strong, of all known substances diamond has the greatest number of atoms per unit volume, why it is both the hardest and the least compressible.
It has a high density, ranging from 3150 to 3530 kilograms per cubic metre in natural diamonds and 3520 kg/m³ in pure diamond. In graphite, the bonds between nearest neighbors are stronger but the bonds between planes are weak, so the planes can slip past each other. Thus, graphite is much softer than diamond. However, the stronger bonds make graphite less flammable. Diamonds have been adapted for many uses because of the material's exceptional physical characteristics. Most notable are its extreme hardness and thermal conductivity, as well as wide bandgap and high optical dispersion. Diamond's ignition point is 720 -- 800 °C in 850 -- 1000 °C in air; the equilibrium pressure and temperature conditions for a transition between graphite and diamond is well established theoretically and experimentally. The pressure changes linearly between 1.7 GPa at 0 K and 12 GPa at 5000 K. However, the phases have a wide region about this line where they can coexist. At normal temperature and pressure, 20 °C and 1 standard atmosphere, the stable phase of carbon is graphite, but diamond is metastable and its rate of conversion to graphite is negligible.
However, at temperatures above about 4500 K, diamond converts to graphite. Rapid conversion of graphite to diamond requires pressures well above the equilibrium line: at 2000 K, a pressure of 35 GPa is needed. Above the triple point, the melting point of diamond increases with increasing pressure. At high pressures and germanium have a BC8 body-centered cubic crystal structure, a similar structure is predicted for carbon at high pressures. At 0 K, the transition is predicted to occur at 1100 GPa; the most common crystal structure of diamond is called diamond cubic. It is formed of unit cells stacked together. Although there are 18 atoms in the figure, each corner atom is shared by eight unit cells and each atom in the center of a face is shared by two, so there are a total of eight atoms per unit cell; each side of the unit cell is 3.57 angstroms in length. A diamond cubic lattice can be thought of as two interpenetrating face-centered cubic lattices with one displaced by 1/4 of the diagonal along a cubic cell, or as one lattice with two atoms associated with each lattice point.
Looked at from a <1 1 1> crystallographic direction, it is formed of layers stacked in a repeating ABCABC... pattern. Diamonds can form an ABAB... structure, known as hexagonal diamond or lonsdaleite, but this is far less common and is formed under different conditions from cubic carbon. Diamonds occur most as euhedral or rounded octahedra and twinned octahedra known as macles; as diamond's crystal structure has a cubic arrangement of the atoms, they have many facets that belong to a cube, rhombicosidodecahedron, tetrakis hexahedron or disdyakis dodecahedron. The crystals can be elongated. Diamonds are found coated in nyf, an opaque gum-like skin; some diamonds have opaque fibers. They are referred to as opaque if the fibers
Bushmeat, wildmeat, or game meat is meat from non-domesticated mammals, reptiles and birds hunted for food in tropical forests. Commercial harvesting and the trade of wildlife is considered a threat to biodiversity. Bushmeat provides a route for a number of serious tropical diseases to spread to humans from their animal hosts, such as HIV/AIDS and Ebola. Bushmeat is used for sustenance in remote areas, while in major towns and cities in bushmeat eating societies it is treated as a delicacy. Today the term bushmeat is used for meat of terrestrial wild or feral mammals, killed for sustenance or commercial purposes throughout the humid tropics of the Americas and Africa. In West Africa, Achatina achatina, a giant African snail, is gathered, sold and monitored as part of the bushmeat trade. To reflect the global nature of hunting of wild animals, Resolution 2.64 of the IUCN General Assembly in Amman in October 2000 referred to wild meat rather than bushmeat. A more worldwide term for terrestrial wild animals is game.
The term bushmeat crisis is sometimes used to describe unsustainable hunting of endangered wild mammals in West and Central Africa and the humid tropics, depending on interpretation. African hunting predates recorded history; the volume of the bushmeat trade in West and Central Africa was estimated at 1-5 million tonnes per year at the turn of the century. According to the Center for International Forestry Research in 2014 5 million tonnes were still being consumed per year in the Congo Basin. For the people of this region, bushmeat represents a primary source of animal protein in the diet, making it a significant commercial industry. According to a 1994 study in Gabon, annual sales were estimated at US$50 million; the study found that bushmeat accounted for more than half of meat sold in local markets, with primates representing 20% of the total bushmeat. Logging concessions operated by companies in African forests have been linked to the bushmeat trade; because they provide roads and other access to remote forests, they are the primary means for the transportation of hunters and meat between forests and urban centres.
Some, including the Congolaise Industrielle du Bois in the Republic of Congo, have partnered with governments and international conservation organizations to regulate the bushmeat trade within the concessions where they operate. Numerous solutions are needed. In the case of Ghana, international over-exploitation of African fishing grounds has increased demand for bushmeat. Both EU-subsidized fleets and local commercial fleets have depleted fish stocks, leaving local people to supplement their diets with animals hunted from nature reserves. Over 30 years of data link sharp declines in both mammal populations and the biomass of 41 wildlife species with a decreased supply of fish. In the case of Liberia in West Africa, bushmeat is eaten and is considered a delicacy. A 2004 public opinion survey found that bushmeat ranked second behind fish among residents of the capital Monrovia as a preferred source of protein. Of households where bushmeat was served, 80% of residents said they cooked it "once in a while", while 13% cooked it once a week and 7% cooked bushmeat daily.
The survey was conducted during the last civil war, bushmeat consumption is now believed to be far higher. There has been extensive literature on the topic of bushmeat, related to field anthropology, the process of ethnology has been repeated in many different regions to ensure accuracy and precision; the transmission of variable retrovirus chains causes zoonotic diseases. Outbreaks of the Ebola virus in the Congo Basin and in Gabon in the 1990s have been associated with the butchering of apes and consumption of their meat. Bushmeat hunters in Central Africa infected with the human T-lymphotropic virus were exposed to wild primates. Results of research on wild chimpanzees in Cameroon indicate that they are infected with the simian foamy virus and constitute a reservoir of HIV-1, a precursor of the acquired immunodeficiency syndrome in humans. There are several distinct strains of HIV, indicating that this cross-species transfer has occurred several times. Simian Immunodeficiency Virus, present in modern day chimpanzees, is derived from older strains of the virus present in the Red Capped Mangabey and Greater Spot-nosed Monkey.
It is that HIV was transferred to humans after having come into contact with infected bushmeat. The Ebola virus, for which the primary host is suspected to be fruit bats, has been linked to bushmeat. Between the first recorded outbreak in 1976 and the largest in 2014, the virus has transferred from animals to humans only 30 times, despite large numbers of bats being killed and sold each year. Bats drop eaten fruits and pulp land mammals such as gorillas and duikers feed on these fallen fruits; this chain of events forms a possible indirect means of transmission from the natural host to animal populations. Although primates and other species may be intermediates, evidence suggests people contract the virus from bats. Since most people buy smoked bushmeat and people preparing the food have the highest risk of infection. Hunters shoot, scavenge or catapult their prey, butcher the bats without gloves, getting bites or scratches and coming in contact with their blood. In 2014, the suspected index case for the Ebola outbreak in West Africa is a two-year-old child in Guéckédou in south-eastern Guinea, the child of a family tha