California is a state in the Pacific Region of the United States. With 39.6 million residents, California is the most populous U. S. the third-largest by area. The state capital is Sacramento; the Greater Los Angeles Area and the San Francisco Bay Area are the nation's second and fifth most populous urban regions, with 18.7 million and 9.7 million residents respectively. Los Angeles is California's most populous city, the country's second most populous, after New York City. California has the nation's most populous county, Los Angeles County, its largest county by area, San Bernardino County; the City and County of San Francisco is both the country's second-most densely populated major city after New York City and the fifth-most densely populated county, behind only four of the five New York City boroughs. California's $3.0 trillion economy is larger than that of any other state, larger than those of Texas and Florida combined, the largest sub-national economy in the world. If it were a country, California would be the 5th largest economy in the world, the 36th most populous as of 2017.
The Greater Los Angeles Area and the San Francisco Bay Area are the nation's second- and third-largest urban economies, after the New York metropolitan area. The San Francisco Bay Area PSA had the nation's highest GDP per capita in 2017 among large PSAs, is home to three of the world's ten largest companies by market capitalization and four of the world's ten richest people. California is considered a global trendsetter in popular culture, innovation and politics, it is considered the origin of the American film industry, the hippie counterculture, fast food, the Internet, the personal computer, among others. The San Francisco Bay Area and the Greater Los Angeles Area are seen as global centers of the technology and entertainment industries, respectively. California has a diverse economy: 58% of the state's economy is centered on finance, real estate services and professional, scientific and technical business services. Although it accounts for only 1.5% of the state's economy, California's agriculture industry has the highest output of any U.
S. state. California is bordered by Oregon to the north and Arizona to the east, the Mexican state of Baja California to the south; the state's diverse geography ranges from the Pacific Coast in the west to the Sierra Nevada mountain range in the east, from the redwood–Douglas fir forests in the northwest to the Mojave Desert in the southeast. The Central Valley, a major agricultural area, dominates the state's center. Although California is well-known for its warm Mediterranean climate, the large size of the state results in climates that vary from moist temperate rainforest in the north to arid desert in the interior, as well as snowy alpine in the mountains. Over time and wildfires have become more pervasive features. What is now California was first settled by various Native Californian tribes before being explored by a number of European expeditions during the 16th and 17th centuries; the Spanish Empire claimed it as part of Alta California in their New Spain colony. The area became a part of Mexico in 1821 following its successful war for independence but was ceded to the United States in 1848 after the Mexican–American War.
The western portion of Alta California was organized and admitted as the 31st state on September 9, 1850. The California Gold Rush starting in 1848 led to dramatic social and demographic changes, with large-scale emigration from the east and abroad with an accompanying economic boom; the word California referred to the Baja California Peninsula of Mexico. The name derived from the mythical island California in the fictional story of Queen Calafia, as recorded in a 1510 work The Adventures of Esplandián by Garci Rodríguez de Montalvo; this work was the fifth in a popular Spanish chivalric romance series that began with Amadis de Gaula. Queen Calafia's kingdom was said to be a remote land rich in gold and pearls, inhabited by beautiful black women who wore gold armor and lived like Amazons, as well as griffins and other strange beasts. In the fictional paradise, the ruler Queen Calafia fought alongside Muslims and her name may have been chosen to echo the title of a Muslim leader, the Caliph. It's possible.
Know ye that at the right hand of the Indies there is an island called California close to that part of the Terrestrial Paradise, inhabited by black women without a single man among them, they lived in the manner of Amazons. They were robust of body with great virtue; the island itself is one of the wildest in the world on account of the craggy rocks. Shortened forms of the state's name include CA, Cal. Calif. and US-CA. Settled by successive waves of arrivals during the last 10,000 years, California was one of the most culturally and linguistically diverse areas in pre-Columbian North America. Various estimates of the native population range from 100,000 to 300,000; the Indigenous peoples of California included more than 70 distinct groups of Native Americans, ranging from large, settled populations living on the coast to groups in the interior. California groups were diverse in their political organization with bands, villages, on the resource-rich coasts, large chiefdoms, such as the Chumash and Salinan.
Trade, intermarriage a
South Africa the Republic of South Africa, is the southernmost country in Africa. It is bounded to the south by 2,798 kilometres of coastline of Southern Africa stretching along the South Atlantic and Indian Oceans. South Africa is the largest country in Southern Africa and the 25th-largest country in the world by land area and, with over 57 million people, is the world's 24th-most populous nation, it is the southernmost country on the mainland of the Eastern Hemisphere. About 80 percent of South Africans are of Sub-Saharan African ancestry, divided among a variety of ethnic groups speaking different African languages, nine of which have official status; the remaining population consists of Africa's largest communities of European and multiracial ancestry. South Africa is a multiethnic society encompassing a wide variety of cultures and religions, its pluralistic makeup is reflected in the constitution's recognition of 11 official languages, the fourth highest number in the world. Two of these languages are of European origin: Afrikaans developed from Dutch and serves as the first language of most coloured and white South Africans.
The country is one of the few in Africa never to have had a coup d'état, regular elections have been held for a century. However, the vast majority of black South Africans were not enfranchised until 1994. During the 20th century, the black majority sought to recover its rights from the dominant white minority, with this struggle playing a large role in the country's recent history and politics; the National Party imposed apartheid in 1948. After a long and sometimes violent struggle by the African National Congress and other anti-apartheid activists both inside and outside the country, the repeal of discriminatory laws began in 1990. Since 1994, all ethnic and linguistic groups have held political representation in the country's liberal democracy, which comprises a parliamentary republic and nine provinces. South Africa is referred to as the "rainbow nation" to describe the country's multicultural diversity in the wake of apartheid; the World Bank classifies South Africa as an upper-middle-income economy, a newly industrialised country.
Its economy is the second-largest in Africa, the 34th-largest in the world. In terms of purchasing power parity, South Africa has the seventh-highest per capita income in Africa; however and inequality remain widespread, with about a quarter of the population unemployed and living on less than US$1.25 a day. South Africa has been identified as a middle power in international affairs, maintains significant regional influence; the name "South Africa" is derived from the country's geographic location at the southern tip of Africa. Upon formation, the country was named the Union of South Africa in English, reflecting its origin from the unification of four separate British colonies. Since 1961, the long form name in English has been the "Republic of South Africa". In Dutch, the country was named Republiek van Zuid-Afrika, replaced in 1983 by the Afrikaans Republiek van Suid-Afrika. Since 1994, the Republic has had an official name in each of its 11 official languages. Mzansi, derived from the Xhosa noun umzantsi meaning "south", is a colloquial name for South Africa, while some Pan-Africanist political parties prefer the term "Azania".
South Africa contains human-fossil sites in the world. Archaeologists have recovered extensive fossil remains from a series of caves in Gauteng Province; the area, a UNESCO World Heritage site, has been branded "the Cradle of Humankind". The sites include one of the richest sites for hominin fossils in the world. Other sites include Gondolin Cave Kromdraai, Coopers Cave and Malapa. Raymond Dart identified the first hominin fossil discovered in Africa, the Taung Child in 1924. Further hominin remains have come from the sites of Makapansgat in Limpopo Province and Florisbad in the Free State Province, Border Cave in KwaZulu-Natal Province, Klasies River Mouth in Eastern Cape Province and Pinnacle Point and Die Kelders Cave in Western Cape Province; these finds suggest that various hominid species existed in South Africa from about three million years ago, starting with Australopithecus africanus. There followed species including Australopithecus sediba, Homo ergaster, Homo erectus, Homo rhodesiensis, Homo helmei, Homo naledi and modern humans.
Modern humans have inhabited Southern Africa for at least 170,000 years. Various researchers have located pebble tools within the Vaal River valley. Settlements of Bantu-speaking peoples, who were iron-using agriculturists and herdsmen, were present south of the Limpopo River by the 4th or 5th century CE, they displaced and absorbed the original Khoisan speakers, the Khoikhoi and San peoples. The Bantu moved south; the earliest ironworks in modern-day KwaZulu-Natal Province are believed to date from around 1050. The southernmost group was the Xhosa people, whose language incorporates certain linguistic traits from the earlier Khoisan people; the Xhosa reached the Great Fish River, in today's Eastern Cape Province. As they migrated, these larger Iron Age populations
The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and completely enclosed by land: on the north by Southern Europe and Anatolia, on the south by North Africa and on the east by the Levant. Although the sea is sometimes considered a part of the Atlantic Ocean, it is identified as a separate body of water. Geological evidence indicates that around 5.9 million years ago, the Mediterranean was cut off from the Atlantic and was or desiccated over a period of some 600,000 years, the Messinian salinity crisis, before being refilled by the Zanclean flood about 5.3 million years ago. It covers an approximate area of 2.5 million km2, representing 0.7 % of the global ocean surface, but its connection to the Atlantic via the Strait of Gibraltar-the narrow strait that connects the Atlantic Ocean to the Mediterranean Sea and separates Spain in Europe from Morocco in Africa- is only 14 km wide. In oceanography, it is sometimes called the Eurafrican Mediterranean Sea or the European Mediterranean Sea to distinguish it from mediterranean seas elsewhere.
The Mediterranean Sea has an average depth of 1,500 m and the deepest recorded point is 5,267 m in the Calypso Deep in the Ionian Sea. The sea is bordered on the north by Europe, the east by Asia, in the south by Africa, it is located between latitudes 30° and 46° N and longitudes 6° W and 36° E. Its west-east length, from the Strait of Gibraltar to the Gulf of Iskenderun, on the southwestern coast of Turkey, is 4,000 km; the sea's average north-south length, from Croatia's southern shore to Libya, is 800 km. The sea was an important route for merchants and travellers of ancient times that allowed for trade and cultural exchange between emergent peoples of the region; the history of the Mediterranean region is crucial to understanding the origins and development of many modern societies. The countries surrounding the Mediterranean in clockwise order are Spain, Monaco, Slovenia, Croatia and Herzegovina, Albania, Turkey, Lebanon, Egypt, Tunisia and Morocco. In addition, the Gaza Strip and the British Overseas Territories of Gibraltar and Akrotiri and Dhekelia have coastlines on the sea.
The Ancient Greeks called the Mediterranean ἡ θάλασσα or sometimes ἡ μεγάλη θάλασσα, ἡ ἡμέτερα θάλασσα, or ἡ θάλασσα ἡ καθ'ἡμᾶς. The Romans called it Mare Mare Internum and, starting with the Roman Empire, Mare Nostrum; the term Mare Mediterrāneum appears later: Solinus used it in the 3rd century, but the earliest extant witness to it is in the 6th century, in Isidore of Seville. It means'in the middle of land, inland' in Latin, a compound of medius, -āneus; the Latin word is a calque of Greek μεσόγειος, from μέσος and γήινος, from γῆ. The original meaning may have been'the sea in the middle of the earth', rather than'the sea enclosed by land'; the Carthaginians called it the "Syrian Sea". In ancient Syrian texts, Phoenician epics and in the Hebrew Bible, it was known as the "Great Sea" or as "The Sea". Another name was the "Sea of the Philistines", from the people inhabiting a large portion of its shores near the Israelites. In Modern Hebrew, it is called HaYam HaTikhon'the Middle Sea'. In Modern Arabic, it is known as al-Baḥr al-Mutawassiṭ'the Middle Sea'.
In Islamic and older Arabic literature, it was Baḥr al-Rūm'the Sea of the Romans' or'the Roman Sea'. At first, that name referred to only the Eastern Mediterranean, but it was extended to the whole Mediterranean. Other Arabic names were Baḥr al-šām'the Sea of Syria' and Baḥr al-Maghrib'the Sea of the West'. In Turkish, it is the Akdeniz'the White Sea'; the origin of the name is not clear, as it is not known in earlier Greek, Byzantine or Islamic sources. It may be to contrast with the Black Sea. In Persian, the name was translated as Baḥr-i Safīd, used in Ottoman Turkish, it is the origin of the colloquial Greek phrase Άσπρη Θάλασσα. Johann Knobloch claims that in Classical Antiquity, cultures in the Levant used colours to refer to the cardinal points: black referred to the north, yellow or blue to east, red to south, white to west; this would explain both the Turkish Akdeniz and the Arab nomenclature described above. Several ancient civilizations were located around the Mediterranean shores and were influenced by their proximity to the sea.
It provided routes for trade and war, as well as food for numerous communities throughout the ages. Due to the shared climate and access to the sea, c
A heath is a shrubland habitat found on free-draining infertile, acidic soils and is characterised by open, low-growing woody vegetation. Moorland is related to high-ground heaths with—especially in Great Britain—a cooler and damper climate. Heaths are fast disappearing and considered a rare habitat in Europe, they form extensive and diverse communities across Australia in humid and sub-humid areas where fire regimes with recurring burning are required for the maintenance of the heathlands. More diverse though less widespread heath communities occur in Southern Africa. Extensive heath communities can be found in the California chaparral, New Caledonia, central Chile and along the shores of the Mediterranean Sea. In addition to these extensive heath areas, the vegetation type is found in scattered locations across all continents, except Antarctica. Heathland is favoured where climatic conditions are hard and dry in summer, soils acidic, of low fertility, sandy and free-draining. Heaths are dominated by low shrubs, 20 centimetres to 2 metres tall.
Heath vegetation can be plant-species rich, heathlands of Australia are home to some 3,700 endemic or typical species in addition to numerous less restricted species. The fynbos heathlands of South Africa are second only to tropical rainforests in plant biodiversity with over 7,000 species. In marked contrast, the tiny pockets of heathland in Europe are depauperate with a flora consisting of heather and gorse; the bird fauna of heathlands are cosmopolitan species of the region. In the depauperate heathlands of Europe, bird species tend to be more characteristic of the community and include Montagu's harrier, the tree pipit. In Australia the heathland avian fauna is dominated by nectar-feeding birds such as honey-eaters and lorikeets although numerous other birds from emus to eagles are common in Australian heathlands. Australian heathlands are home to the world's only nectar-feeding terrestrial mammal: the honey possum; the bird fauna of the South African fynbos includes sunbirds and siskins.
Heathlands are an excellent habitat for insects including ants, moths and wasps with many species being restricted to it. One such example of an organism restricted to heathland is the silver-studded blue butterfly, Plebejus argus. Anthropogenic heath habitats are a cultural landscape that can be found worldwide in locations as diverse as northern and western Europe, the Americas, New Zealand and New Guinea; these heaths were created or expanded by centuries of human clearance of the natural forest and woodland vegetation, by grazing and burning. In some cases this clearance went so far that parts of the heathland have given way to open spots of pure sand and sand dunes, with a local climate that in Europe, can experience temperatures of 50 °C in summer, drying the sand spot bordering the heathland and further raising its vulnerability for wildfires. Referring to heathland in England, Oliver Rackham says, "Heaths are the product of human activities and need to be managed as heathland. In recent years the conservation value of these man-made heaths has become much more appreciated, most heathlands are protected.
However they are threatened by tree incursion because of the discontinuation of traditional management techniques such as grazing and burning that mediated the landscapes. Some are threatened by urban sprawl. Anthropogenic heathlands are maintained artificially by a combination of grazing and periodic burning, or mowing; the re-colonising tree species will depend on what is available as the local seed source, thus it may not reflect the natural vegetation before the heathland became established. Bolster heath Chalk heath Garrigue Maquis shrubland Matorral Scrubland The Countryside Agency information on types of open land Origin of the word'heath'
A cactus is a member of the plant family Cactaceae, a family comprising about 127 genera with some 1750 known species of the order Caryophyllales. The word "cactus" derives, through Latin, from the Ancient Greek κάκτος, kaktos, a name used by Theophrastus for a spiny plant whose identity is not certain. Cacti occur in a wide range of sizes. Most cacti live in habitats subject to at least some drought. Many live in dry environments being found in the Atacama Desert, one of the driest places on earth. Cacti show many adaptations to conserve water. All cacti are succulents, meaning they have thickened, fleshy parts adapted to store water. Unlike many other succulents, the stem is the only part of most cacti where this vital process takes place. Most species of cacti have lost true leaves, retaining only spines, which are modified leaves; as well as defending against herbivores, spines help prevent water loss by reducing air flow close to the cactus and providing some shade. In the absence of leaves, enlarged stems carry out photosynthesis.
Cacti are native to the Americas, ranging from Patagonia in the south to parts of western Canada in the north—except for Rhipsalis baccifera, which grows in Africa and Sri Lanka. Cactus spines are produced from specialized structures called areoles, a kind of reduced branch. Areoles are an identifying feature of cacti; as well as spines, areoles give rise to flowers, which are tubular and multipetaled. Many cacti have short growing seasons and long dormancies, are able to react to any rainfall, helped by an extensive but shallow root system that absorbs any water reaching the ground surface. Cactus stems are ribbed or fluted, which allows them to expand and contract for quick water absorption after rain, followed by long drought periods. Like other succulent plants, most cacti employ a special mechanism called "crassulacean acid metabolism" as part of photosynthesis. Transpiration, during which carbon dioxide enters the plant and water escapes, does not take place during the day at the same time as photosynthesis, but instead occurs at night.
The plant stores the carbon dioxide it takes in as malic acid, retaining it until daylight returns, only using it in photosynthesis. Because transpiration takes place during the cooler, more humid night hours, water loss is reduced. Many smaller cacti have globe-shaped stems, combining the highest possible volume for water storage, with the lowest possible surface area for water loss from transpiration; the tallest free-standing cactus is Pachycereus pringlei, with a maximum recorded height of 19.2 m, the smallest is Blossfeldia liliputiana, only about 1 cm in diameter at maturity. A grown saguaro is said to be able to absorb as much as 200 U. S. gallons of water during a rainstorm. A few species differ in appearance from most of the family. At least superficially, plants of the genus Pereskia resemble other trees and shrubs growing around them, they have persistent leaves, when older, bark-covered stems. Their areoles identify them as cacti, in spite of their appearance, too, have many adaptations for water conservation.
Pereskia is considered close to the ancestral species from. In tropical regions, other cacti grow as forest epiphytes, their stems are flattened leaf-like in appearance, with fewer or no spines, such as the well-known Christmas cactus or Thanksgiving cactus. Cacti have a variety of uses: many species are used as ornamental plants, others are grown for fodder or forage, others for food. Cochineal is the product of an insect. Many succulent plants in both the Old and New World – such as some Euphorbiaceae – bear a striking resemblance to cacti, may incorrectly be called "cactus" in common usage; the 1,500 to 1,800 species of cacti fall into one of two groups of "core cacti": opuntias and "cactoids". Most members of these two groups are recognizable as cacti, they have fleshy succulent stems. They have small, or transient leaves, they have flowers with ovaries that lie below the sepals and petals deeply sunken into a fleshy receptacle. All cacti have areoles—highly specialized short shoots with short internodes that produce spines, normal shoots, flowers.
The remaining cacti fall into only two genera and Maihuenia, are rather different, which means any description of cacti as a whole must make exceptions for them. Pereskia species superficially resemble other tropical forest trees; when mature, they have woody stems that may be covered with bark and long-lasting leaves that provide the main means of photosynthesis. Their flowers may have superior ovaries, areoles that produce further leaves; the two species of Maihuenia have globe-shaped bodies with prominent leaves at the top. Cacti show a wide variety of growth habits, which are difficult to divide into clear, simple categories. Arborescent cactiThey can be tree-like, meaning they have a single more-or-less woody trunk topped by several to many branches. In the genus Pereskia, the branches are covered with leaves, so the species of this genus may not be recognized as cacti. In most other cacti, the branches are more cactus-like, bare of leaves and bark, cov
World Wide Fund for Nature
The World Wide Fund for Nature is an international non-governmental organization founded in 1961, working in the field of the wilderness preservation, the reduction of human impact on the environment. It was named the World Wildlife Fund, which remains its official name in Canada and the United States. WWF is the world's largest conservation organization with over five million supporters worldwide, working in more than 100 countries, supporting around 1,300 conservation and environmental projects, they have invested over $1 billion in more than 12,000 conservation initiatives since 1995. WWF is a foundation with 55% of funding from individuals and bequests, 19% from government sources and 8% from corporations in 2014. WWF aims to "stop the degradation of the planet's natural environment and to build a future in which humans live in harmony with nature." The Living Planet Report is published every two years by WWF since 1998. In addition, WWF has launched several notable worldwide campaigns including Earth Hour and Debt-for-Nature Swap, its current work is organized around these six areas: food, freshwater, wildlife and oceans.
WWF has been accused by BuzzFeed News, Kathmandu Post, the Rainforest Foundation Fund and Survival International of protecting paramilitary forces funded by the organization to fight poaching that have engaged in human rights abuses despite an internal report acknowledging them in 2015. They have attacked African and South Asian villages, torturing and killing villagers. Investigators revealed that the WWF engaged in cover ups and lobbied to release rangers when they were arrested; the Conservation Foundation, a precursor to WWF, was founded in 1948 by Fairfield Osborn as an affiliate of the New York Zoological Society with an aim of protecting the world's natural resources. The advisory council included leading scientists such as Charles Sutherland Elton, G. Evelyn Hutchinson, Aldo Leopold, Carl Sauer, Paul Sears, it supported much of the scientific work cited by Rachel Carson's Silent Spring, including that of John L. George, Roger Hale, Robert Rudd, George Woodwell; the idea for a fund on behalf of endangered animals was proposed by Victor Stolan to Sir Julian Huxley in response to articles he published in the British newspaper The Observer.
This proposal led Huxley to put Stolan in contact with Max Nicholson, a person who had had thirty years experience of linking progressive intellectuals with big business interests through the Political and Economic Planning think tank. Nicholson thought up the name of the organization. WWF was conceived on 29 April 1961, under the name of World Wildlife Fund, its first office was opened on 11 September that same year in Morges, Switzerland. WWF was conceived to act as a funding institution for existing conservation groups such as the International Union for the Conservation of Nature and Natural Resources and The Conservation Foundation. Godfrey A. Rockefeller played an important role in its creation, assembling the first staff, its establishment was marked with the signing of the "Morges Manifesto", the founding document that sets out the fund's commitment to assisting worthy organizations struggling to save the world's wildlife: They need above all money, to carry out mercy missions and to meet conservation emergencies by buying land where wildlife treasures are threatened, in many other ways.
Money, for example, to pay guardians of wildlife refuges.... Money for education and propaganda among those who would care and help if only they understood. Money to send out experts to danger spots and to train more local wardens and helpers in Africa and elsewhere. Money to maintain a sort of'war room' at the international headquarters of conservation, showing where the danger spots are and making it possible to ensure that their needs are met before it is too late. Dutch Prince Bernhard of Lippe-Biesterfeld helped found the World Wildlife Fund, becoming its first President in 1961. In 1963, the Foundation held a conference and published a major report warning of anthropogenic global warming, written by Noel Eichhorn based on the work of Frank Fraser Darling, Edward Deevey, Erik Eriksson, Charles Keeling, Gilbert Plass, Lionel Walford, William Garnett. In 1970, along with Duke of Edinburgh and a few associates, Prince Bernhard established the WWF's financial endowment The 1001: A Nature Trust to handle the WWF's administration and fund-raising.
1001 members each contributed $10,000 to the trust. Prince Bernhard resigned his post after being involved in the Lockheed Bribery Scandal. WWF has set up operations around the world, it worked by fundraising and providing grants to existing non-governmental organizations, based on the best-available scientific knowledge and with an initial focus on the protection of endangered species. As more resources became available, its operations expanded into other areas such as the preservation of biological diversity, sustainable use of natural resources, the reduction of pollution, climate change; the organization began to run its own conservation projects and campaigns, by the 1980s started to take a more strategic approach to its conservation activities. In 1986, the organization changed its name to World Wide Fund for Nature, while retaining the WWF initials. However, it continued at that time to operate under the original name in the United States and Canada; that year was the 25th anniversary of WWF's foundation, an event marked by a gathering in Assisi, Italy to which the organization's International President HRH Prince Philip, the Duke of Edinburgh, invited religi
Browsing is a type of herbivory in which a herbivore feeds on leaves, soft shoots, or fruits of high-growing woody plants such as shrubs. This is contrasted with grazing associated with animals feeding on grass or other low vegetation. Alternatively, grazers are animals eating grass, browsers are animals eating non-grasses, which include both woody and herbaceous dicots. In either case, an example of this dichotomy are goats and sheep; the plant material eaten is known as browse and is taken straight from the plant, though owners of livestock such as goats and deer may cut twigs or branches for feeding to their stock. In temperate regions, owners take browse before leaf fall dry and store it as a winter feed supplement. In time of drought, herdsmen may cut branches from beyond the reach of their stock, as forage at ground level. In the tropical regions, where population pressure leads owners to resort to this more there is a danger of permanent depletion of the supply. Animals in captivity may be fed browse as a replacement for their wild food sources.
If the population of browsers grows too high, all of the browse that they can reach may be devoured. The resulting level below which few or no leaves are found is known as the browse line. If over-browsing continues for too long, the ability of the ecosystem's trees to reproduce may be impaired, as young plants cannot survive long enough to grow too tall for browsers to reach. Overbrowsing occurs when overpopulated or densely concentrated herbivores exert extreme pressure on plants, reducing the carrying capacity and altering the ecological functions of their habitat. Examples of overbrowsing herbivores around the world include Koala in Southern Australia, introduced mammals in New Zealand, cervids in forests of North America and Europe. Deer exclosures are used to determine the ecological impacts of cervids, allowing scientists to compare flora and soil in areas inside and outside of exclosures. Changes in plant communities in response to herbivory reflect the differential palatability of plants to the overabundant herbivore as well as the variable ability of plants to tolerate high levels of browsing.
Compositional and structural changes in forest vegetation can have cascading effects on the entire ecosystem including impacts on soil quality and stability, micro- and macro-invertebrates, small mammals and even large predators. There are several causes of subsequent overbrowsing. Herbivores are introduced to landscapes in which native plants have not evolved to withstand browsing, predators have not adapted to hunt the invading species. In other cases, populations of herbivores exceed historic levels due to reduced hunting or predation pressure. For example, carnivores declined in North America throughout the last century and hunting regulations became stricter, contributing to increased cervid populations across North America. Landscape changes due to human development, such as in agriculture and forestry, can create fragmented forest patches between which deer travel, browsing in early successional habitat at the periphery. Agricultural fields and young silvicultural stands provide deer with high quality food leading to overabundance and increased browsing pressure on forest understory plants.
Overbrowsing impacts plants at individual and community levels. The negative effects of browsing are greater among intolerant species, such as members of the genus Trillium, which have all photosynthetic tissues and reproductive organs at the apex of a singular stem; this means that a deer may eat all the reproductive and photosynthetic tissues at once, reducing the plant’s height, photosynthetic capabilities, reproductive output. This is one example of how overbrowsing can lead to the loss of reproductive individuals in a population, a lack of recruitment of young plants. Plants differ in their palatability to herbivores. At high densities of herbivores, plants that are selected as browse may be missing small and large individuals from the population. At the community level, intense browsing by deer in forests leads to reductions in the abundance of palatable understory herbaceous shrubs, increases in graminoid and bryophyte abundance which are released from competition for light. Overbrowsing can change near-ground forest structure, plant species composition, vegetation density, leaf litter, with consequences for other forest-dwelling animals.
Many species of ground-dwelling invertebrates rely on near-ground vegetation cover and leaf litter layers for habitat. Further, preferential selection of certain plant species by herbivores can impact invertebrates associated with those plants. Migratory forest-dwelling songbirds depend on dense understory vegetation for nesting and foraging habitat and reductions in understory plant biomass caused by deer can lead to declines in forest songbird populations. Loss of understory plant diversity associated with ungulate overbrowsing can impact small mammals that rely on this vegetation for cover and food. Overbrowsing can lead plant communities towards equilibrium states which are only reversible if herbivore numbers are reduced for a sufficient period, actions are taken to restore the original plant communities. Management to reduce deer populations takes a three-pronged approach: large areas of contiguous old for