Overexploitation

Overexploitation, also called overharvesting, refers to harvesting a renewable resource to the point of diminishing returns. Continued overexploitation can lead to the destruction of the resource. The term applies to natural resources such as: wild medicinal plants, grazing pastures, game animals, fish stocks, forests, and water aquifers.

In ecology, overexploitation describes one of the five main activities threatening global biodiversity.[2] Ecologists use the term to describe populations that are harvested at a rate that is unsustainable, given their natural rates of mortality and capacities for reproduction. This can result in extinction at the population level and even extinction of whole species. In conservation biology the term is usually used in the context of human economic activity that involves the taking of biological resources, or organisms, in larger numbers than their populations can withstand.[3] The term is also used and defined somewhat differently in fisheries, hydrology and natural resource management.

Overexploitation can lead to resource destruction, including extinctions. However it is also possible for overexploitation to be sustainable, as discussed below in the section on fisheries. In the context of fishing, the term overfishing can be used instead of overexploitation, as can overgrazing in stock management, overlogging in forest management, overdrafting in aquifer management, and endangered species in species monitoring. Overexploitation is not an activity limited to humans. Introduced predators and herbivores, for example, can overexploit native flora and fauna.

Surexploitation morue surpêcheEn
Atlantic cod stocks were severely overexploited in the 1970s and 1980s, leading to their abrupt collapse in 1992.[1]

History

Giant Haasts eagle attacking New Zealand moa
When the giant flightless birds called moa were overexploited to the point of extinction,[4] the giant Haast's eagle that preyed on them also became extinct.[5]

Concern about overexploitation is relatively recent, though overexploitation itself is not a new phenomenon. It has been observed for millennia. For example, ceremonial cloaks worn by the Hawaiian kings were made from the mamo bird; a single cloak used the feathers of 70,000 birds of this now-extinct species. The dodo, a flightless bird from Mauritius, is another well-known example of overexploitation. As with many island species, it was naive about certain predators, allowing humans to approach and kill it with ease.[6]

From the earliest of times, hunting has been an important human activity as a means of survival. There is a whole history of overexploitation in the form of overhunting. The overkill hypothesis (Quaternary extinction events) explains why the megafaunal extinctions occurred within a relatively short period of time. This can be traced with human migration. The most convincing evidence of this theory is that 80% of the North American large mammal species disappeared within 1000 years of the arrival of humans on the western hemisphere continents.[7] The fastest ever recorded extinction of megafauna occurred in New Zealand, where by 1500 AD, just 200 years after settling the islands, ten species of the giant moa birds were hunted to extinction by the Māori.[4] A second wave of extinctions occurred later with European settlement.

In more recent times, overexploitation has resulted in the gradual emergence of the concepts of sustainability and sustainable development, which has built on other concepts, such as sustainable yield,[8] eco-development[9][10] and deep ecology.[11][12]

Overview

Overexploitation doesn't necessarily lead to the destruction of the resource, nor is it necessarily unsustainable. However, depleting the numbers or amount of the resource can change its quality. For example, footstool palm is a wild palm tree found in Southeast Asia. Its leaves are used for thatching and food wrapping, and overharvesting has resulted in its leaf size becoming smaller.

Tragedy of the commons

Cows on Selsley Common - geograph.org.uk - 192472
Cows on Selsley Common. The tragedy of the commons is a useful parable for understanding how overexploitation can occur.

In 1968, the journal Science published an article by Garrett Hardin entitled "The Tragedy of the Commons".[13] It was based on a parable that William Forster Lloyd published in 1833 to explain how individuals innocently acting in their own self interest can overexploit, and destroy, a resource that they all share.[14] Lloyd described a simplified hypothetical situation based on medieval land tenure in Europe. Herders share common land on which they are each entitled to graze their cows. In Hardin's article, it is in each herder's individual interest to graze each new cow that the herder acquires on the common land, even if the carrying capacity of the common is exceeded, which damages the common for all the herders. The self-interested herder receives all of the benefits of having the additional cow, while all the herders share the damage to the common. However, all herders reach the same rational decision to buy additional cows and graze them on the common, which eventually destroys the common. Hardin concludes:

Therein is the tragedy. Each man is locked into a system that compels him to increase his herd without limit—in a world that is limited. Ruin is the destination toward which all men rush, each pursuing his own interest in a society that believes in the freedom of the commons. Freedom in a commons brings ruin to all.[13]:1244

In the course of his essay, Hardin develops the theme, drawing in many examples of latter day commons, such as national parks, the atmosphere, oceans, rivers and fish stocks. The example of fish stocks had led some to call this the "tragedy of the fishers".[15] A major theme running through the essay is the growth of human populations, with the Earth's finite resources being the general common.

The tragedy of the commons has intellectual roots tracing back to Aristotle, who noted that "what is common to the greatest number has the least care bestowed upon it",[16] as well as to Hobbes and his Leviathan.[17] The opposite situation to a tragedy of the commons is sometimes referred to as a tragedy of the anticommons: a situation in which rational individuals, acting separately, collectively waste a given resource by underutilizing it.

The tragedy of the commons can be avoided if it is appropriately regulated. Hardin's use of "commons" has frequently been misunderstood, leading Hardin to later remark that he should have titled his work "The tragedy of the unregulated commons".[18]

Fisheries

Bluefin-big
The Atlantic bluefin tuna is currently seriously overexploited. Scientists say 7,500 tons annually is the sustainable limit, yet the fishing industry continue to harvest 60,000 tons.

In wild fisheries, overexploitation or overfishing occurs when a fish stock has been fished down "below the size that, on average, would support the long-term maximum sustainable yield of the fishery".[19] However, overexploitation can be sustainable.

When a fishery starts harvesting fish from a previously unexploited stock, the biomass of the fish stock will decrease, since harvesting means fish are being removed. For sustainability, the rate at which the fish replenish biomass through reproduction must balance the rate at which the fish are being harvested. If the harvest rate is increased, then the stock biomass will further decrease. At a certain point, the maximum harvest yield that can be sustained will be reached, and further attempts to increase the harvest rate will result in the collapse of the fishery. This point is called the maximum sustainable yield, and in practice, usually occurs when the fishery has been fished down to about 30% of the biomass it had before harvesting started.[20]

It is possible to fish the stock down further to, say, 15% of the pre-harvest biomass, and then adjust the harvest rate so the biomass remains at that level. In this case, the fishery is sustainable, but is now overexploited, because the stock has been run down to the point where the sustainable yield is less than it could be.

Fish stocks are said to "collapse" if their biomass declines by more than 95 percent of their maximum historical biomass. Atlantic cod stocks were severely overexploited in the 1970s and 1980s, leading to their abrupt collapse in 1992.[1] Even though fishing has ceased, the cod stocks have failed to recover.[1] The absence of cod as the apex predator in many areas has led to trophic cascades.[1]

About 25% of world fisheries are now overexploited to the point where their current biomass is less than the level that maximizes their sustainable yield.[21] These depleted fisheries can often recover if fishing pressure is reduced until the stock biomass returns to the optimal biomass. At this point, harvesting can be resumed near the maximum sustainable yield.[22]

The tragedy of the commons can be avoided within the context of fisheries if fishing effort and practices are regulated appropriately by fisheries management. One effective approach may be assigning some measure of ownership in the form of individual transferable quotas (ITQs) to fishermen. In 2008, a large scale study of fisheries that used ITQs, and ones that didn't, provided strong evidence that ITQs help prevent collapses and restore fisheries that appear to be in decline.[23][24]

Water resources

PeakWaterAquifer
Overexploitation of groundwater from an aquifer can result in a peak water curve.[25]

Water resources, such as lakes and aquifers, are usually renewable resources which naturally recharge (the term fossil water is sometimes used to describe aquifers which don't recharge). Overexploitation occurs if a water resource, such as the Ogallala Aquifer, is mined or extracted at a rate that exceeds the recharge rate, that is, at a rate that exceeds the practical sustained yield. Recharge usually comes from area streams, rivers and lakes. An aquifer which has been overexploited is said to be overdrafted or depleted. Forests enhance the recharge of aquifers in some locales, although generally forests are a major source of aquifer depletion.[26][27] Depleted aquifers can become polluted with contaminants such as nitrates, or permanently damaged through subsidence or through saline intrusion from the ocean.

This turns much of the world's underground water and lakes into finite resources with peak usage debates similar to oil.[28][29] These debates usually centre around agriculture and suburban water usage but generation of electricity from nuclear energy or coal and tar sands mining is also water resource intensive.[30] A modified Hubbert curve applies to any resource that can be harvested faster than it can be replaced.[25] Though Hubbert's original analysis did not apply to renewable resources, their overexploitation can result in a Hubbert-like peak. This has led to the concept of peak water.

Forest resources

Gordon River Clearcut
Clear cutting of old growth forests in Canada.

Forests are overexploited when they are logged at a rate faster than reforestation takes place. Reforestation competes with other land uses such as food production, livestock grazing, and living space for further economic growth. Historically utilization of forest products, including timber and fuel wood, have played a key role in human societies, comparable to the roles of water and cultivable land. Today, developed countries continue to utilize timber for building houses, and wood pulp for paper. In developing countries almost three billion people rely on wood for heating and cooking.[31] Short-term economic gains made by conversion of forest to agriculture, or overexploitation of wood products, typically leads to loss of long-term income and long term biological productivity. West Africa, Madagascar, Southeast Asia and many other regions have experienced lower revenue because of overexploitation and the consequent declining timber harvests.[32]

Biodiversity

Maldivesfish2
The rich diversity of marine life inhabiting coral reefs attracts bioprospectors. Many coral reefs are overexploited; threats include coral mining, cyanide and blast fishing, and overfishing in general.

Overexploitation is one of the main threats to global biodiversity.[2] Other threats include pollution, introduced and invasive species, habitat fragmentation, habitat destruction,[2] uncontrolled hybridization,[33] global warming,[34] ocean acidification[35] and the driver behind many of these, human overpopulation.[36]

One of the key health issues associated with biodiversity is drug discovery and the availability of medicinal resources.[37] A significant proportion of drugs are natural products derived, directly or indirectly, from biological sources. Marine ecosystems are of particular interest in this regard.[38] However unregulated and inappropriate bioprospecting could potentially lead to overexploitation, ecosystem degradation and loss of biodiversity.[39][40][41]

Endangered species

Overgrazing
It is not just humans that overexploit resources. Overgrazing can be caused by native fauna, as shown in the upper right. However, past human overexploitation (leading to elimination of some predators) may be behind the situation.

Overexploitation threatens one-third of endangered vertebrates, as well as other groups. Excluding edible fish, the illegal trade in wildlife is valued at $10 billion per year. Industries responsible for this include the trade in bushmeat, the trade in Chinese medicine, and the fur trade.[42] The Convention for International Trade in Endangered Species of Wild Fauna and Flora, or CITES was set up in order to control and regulate the trade in endangered animals. It currently protects, to a varying degree, some 33,000 species of animals and plants. It is estimated that a quarter of the endangered vertebrates in the United States of America and half of the endangered mammals is attributed to overexploitation.[2][43]

All living organisms require resources to survive. Overexploitation of these resources for protracted periods can deplete natural stocks to the point where they are unable to recover within a short time frame. Humans have always harvested food and other resources they have needed to survive. Human populations, historically, were small, and methods of collection limited to small quantities. With an exponential increase in human population, expanding markets and increasing demand, combined with improved access and techniques for capture, are causing the exploitation of many species beyond sustainable levels.[44] In practical terms, if continued, it reduces valuable resources to such low levels that their exploitation is no longer sustainable and can lead to the extinction of a species, in addition to having dramatic, unforeseen effects, on the ecosystem.[45] Overexploitation often occurs rapidly as markets open, utilising previously untapped resources, or locally used species.

Conuropsis carolinensisAWP026AA2
The Carolina parakeet was hunted to extinction.

Today, overexploitation and misuse of natural resources is an ever-present threat for species richness. This is more prevalent when looking at island ecology and the species that inhabit them, as islands can be viewed as the world in miniature. Island endemic populations are more prone to extinction from overexploitation, as they often exist at low densities with reduced reproductive rates.[46] A good example of this are island snails, such as the Hawaiian Achatinella and the French Polynesian Partula. Achatinelline snails have 15 species listed as extinct and 24 critically endangered[47] while 60 species of partulidae are considered extinct with 14 listed as critically endangered.[48] The WCMC have attributed over-collecting and very low lifetime fecundity for the extreme vulnerability exhibited among these species.[49]

As another example, when the humble hedgehog was introduced to the Scottish island of Uist, the population greatly expanded and took to consuming and overexploiting shorebird eggs, with drastic consequences for their breeding success. Twelve species of avifauna are affected, with some species numbers being reduced by 39%.[50]

Where there is substantial human migration, civil unrest, or war, controls may no longer exist. With civil unrest, for example in the Congo and Rwanda, firearms have become common and the breakdown of food distribution networks in such countries leaves the resources of the natural environment vulnerable.[51] Animals are even killed as target practice, or simply to spite the government. Populations of large primates, such as gorillas and chimpanzees, ungulates and other mammals, may be reduced by 80% or more by hunting, and certain species may be eliminated altogether.[52] This decline has been called the bushmeat crisis.

Overall, 50 bird species that have become extinct since 1500 (approximately 40% of the total) have been subject to overexploitation,[53] including:

  • Great Auk – the penguin-like bird of the north, was hunted for its feathers, meat, fat and oil.
  • Carolina parakeet – The only parrot species native to the eastern United States, was hunted for crop protection and its feathers.

Other species affected by overexploitation include:

  • The international trade in fur: chinchilla, vicuña, giant otter and numerous cat species
  • Insect collectors: butterflies
  • Horticulturists: New Zealand mistletoe (Trilepidia adamsii), orchids, cacti and many other plant species
  • Shell collectors: Marine molluscs
  • Aquarium hobbyists: tropical fish
  • Chinese medicine: bears, tigers, rhinos, seahorses, Asian black bear and saiga antelope[54]
  • Novelty pets: snakes, parrots, primates and big cats

Cascade effects

Kelp forest
Overexploiting sea otters resulted in cascade effects which destroyed kelp forest ecosystems.

Overexploitation of species can result in knock-on or cascade effects. This can particularly apply if, through overexploitation, a habitat loses its apex predator. Because of the loss of the top predator, a dramatic increase in their prey species can occur. In turn, the unchecked prey can then overexploit their own food resources until population numbers dwindle, possibly to the point of extinction.

A classic example of cascade effects occurred with sea otters. Starting before the 17th century and not phased out until 1911, sea otters were hunted aggressively for their exceptionally warm and valuable pelts, which could fetch up to $2500 US. This caused cascade effects through the kelp forest ecosystems along the Pacific Coast of North America.[55]

One of the sea otters’ primary food sources is the sea urchin. When hunters caused sea otter populations to decline, an ecological release of sea urchin populations occurred. The sea urchins then overexploited their main food source, kelp, creating urchin barrens, areas of seabed denuded of kelp, but carpeted with urchins. No longer having food to eat, the sea urchin became locally extinct as well. Also, since kelp forest ecosystems are homes to many other species, the loss of the kelp caused other cascade effects of secondary extinctions.[56]

In 1911, when only one small group of 32 sea otters survived in a remote cove, an international treaty was signed to prevent further exploitation of the sea otters. Under heavy protection, the otters multiplied and repopulated the depleted areas, which slowly recovered. More recently, with declining numbers of fish stocks, again due to overexploitation, killer whales have experienced a food shortage and have been observed feeding on sea otters, again reducing their numbers.[57]

See also

Notes

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References

Bay of Bengal

The Bay of Bengal is the northeastern part of the Indian Ocean, bounded on the west and northwest by India, on the north by Bangladesh, and on the east by Myanmar and the Andaman Islands of India and Myanmar and the Nicobar Islands of India. Its southern limit is a line between Sri Lanka and the northwesternmost point of Sumatra (Indonesia). It is the largest water region called a bay in the world. There are countries dependent on the Bay of Bengal in South Asia and Southeast Asia.

The Bay of Bengal occupies an area of 2,172,000 square kilometres (839,000 sq mi). A number of large rivers flow into the Bay of Bengal: the Ganges–Hooghly, the Padma, the Brahmaputra–Jamuna, the Barak–Surma–Meghna, the Irrawaddy, the Godavari, the Mahanadi, the Brahmani, the Baitarani, the Krishna and the Kaveri. Among the important ports are Chennai-Ennore, Chittagong, Colombo, Kolkata-Haldia, Mongla, Paradip, Port Blair, Tuticorin, Visakhapatnam and Dhamra. Among the smaller ports are Gopalpur Port, Kakinada and Payra.

Blyth's tragopan

Blyth’s tragopan (Tragopan blythii) or the grey-bellied tragopan is a pheasant that is a vulnerable species. The common name commemorates Edward Blyth (1810–1873), English zoologist and Curator of the Museum of the Asiatic Society of Bengal.

Cascade effect (ecology)

An ecological cascade effect is a series of secondary extinctions that is triggered by the primary extinction of a key species in an ecosystem. Secondary extinctions are likely to occur when the threatened species are: dependent on a few specific food sources, mutualistic (dependent on the key species in some way), or forced to coexist with an invasive species that is introduced to the ecosystem. Species introductions to a foreign ecosystem can often devastate entire communities, and even entire ecosystems. These exotic species monopolize the ecosystem's resources, and since they have no natural predators to decrease their growth, they are able to increase indefinitely. Olsen et al. showed that exotic species have caused lake and estuary ecosystems to go through cascade effects due to loss of algae, crayfish, mollusks, fish, amphibians, and birds. However, the principal cause of cascade effects is the loss of top predators as the key species. As a result of this loss, a dramatic increase (ecological release) of prey species occurs. The prey is then able to overexploit its own food resources, until the population numbers decrease in abundance, which can lead to extinction. When the prey's food resources disappear, they starve and may go extinct as well. If the prey species is herbivorous, then their initial release and exploitation of the plants may result in a loss of plant biodiversity in the area. If other organisms in the ecosystem also depend upon these plants as food resources, then these species may go extinct as well. An example of the cascade effect caused by the loss of a top predator is apparent in tropical forests. When hunters cause local extinctions of top predators, the predators' prey's population numbers increase, causing an overexploitation of a food resource and a cascade effect of species loss. Recent studies have been performed on approaches to mitigate extinction cascades in food-web networks.

Catch per unit effort

In fisheries and conservation biology, the catch per unit effort (CPUE) is an indirect measure of the abundance of a target species. Changes in the catch per unit effort are inferred to signify changes to the target species' true abundance. A decreasing CPUE indicates overexploitation, while an unchanging CPUE indicates sustainable harvesting.CPUE has a number of advantages over other methods of measuring abundance. It does not interfere with routine harvesting operations, and data are easily collected. The data are also easy to analyse, even for non-specialists, in contrast to methods based on transects. This means that decisions about stock management can also be made by the people doing the harvesting. The best practice is to standardise the effort employed (e.g. number of traps or duration of searching), which controls for the reduction in catch size that often results from subsequent efforts.Although CPUE is a relative measure of abundance, it can be used to estimate absolute abundances. The main difficulty when using measures of CPUE is to define the unit of effort.

Cordylus

The genus Cordylus (Sauria: Cordylidae) includes a wide variety of small- to medium-sized spiny lizards from Africa, collectively called girdle-tailed or girdled lizards. All are diurnal and ovoviviparous (live-bearing, without shelled eggs). Most species are rupicolous (rock-dwelling), while a few species are arboreal or live in burrows. They defend themselves with osteoderms (flat bony plates in the skin) and by quickly retreating into rock crevices or burrows. Many species live in groups and males defend territories.

Cordylids are generally listed under CITES Appendix II. They are not necessarily threatened with extinction, but trade is controlled to prevent overexploitation. Some species of Cordylus have limited ranges and may be threatened with habitat destruction or over collecting for the pet trade.

Defaunation

Defaunation is the global, local or functional extinction of animal populations or species from ecological communities. The growth of the human population, combined with advances in harvesting technologies, has led to more intense and efficient exploitation of the environment. This has resulted in the depletion of large vertebrates from ecological communities, creating what has been termed "empty forest". Defaunation differs from extinction; it includes both the disappearance of species and declines in abundance. Defaunation effects were first implied at the Symposium of Plant-Animal Interactions at the University of Campinas, Brazil in 1988 in the context of neotropical forests. Since then, the term has gained broader usage in conservation biology as a global phenomenon.It is estimated that more than 50 percent of all wildlife has been lost in the last 40 years. in 2020 it is estimated that 68% of the world's wildlife will be lost. In South America, there is believed to be a 70 percent loss.In November 2017, over 15,000 scientists around the world issued a second warning to humanity, which, among other things, urged for the development and implementation of policies to halt "defaunation, the poaching crisis, and the exploitation and trade of threatened species."

Depensation

In population dynamics, depensation is the effect on a population (such as a fish stock) whereby, due to certain causes, a decrease in the breeding population (mature individuals) leads to reduced production and survival of eggs or offspring. The causes may include predation levels rising per offspring (given the same level of overall predator pressure) and the allee effect, particularly the reduced likelihood of finding a mate.

Desertification

Desertification is a type of land degradation in which a relatively dry area of land becomes a desert, typically losing its bodies of water as well as vegetation and wildlife. It is caused by a variety of factors, such as through climate change (particularly the current global warming) and through the overexploitation of soil through human activity. When deserts appear automatically over the natural course of a planet's life cycle, then it can be called a natural phenomenon; however, when deserts emerge due to the rampant and unchecked depletion of nutrients in soil that are essential for it to remain arable, then a virtual "soil death" can be spoken of, which traces its cause back to human overexploitation. Desertification is a significant global ecological and environmental problem with far reaching consequences on socio-economic and political conditions.

Duiker

A duiker is a small to medium-sized brown antelope native to sub-Saharan Africa, found in heavily wooded areas. The 22 extant species, including three sometimes considered to be subspecies of the other species, form the subfamily Cephalophinae.

Ecological yield

Ecological yield is the harvestable population growth of an ecosystem. It is most commonly measured in forestry: sustainable forestry is defined as that which does not harvest more wood in a year than has grown in that year, within a given patch of forest.

However, the concept is also applicable to water, soil, and any other aspect of an ecosystem which can be both harvested and renewed—called renewable resources. The carrying capacity of an ecosystem is reduced over time if more than the amount which is "renewed" (refreshed or regrown or rebuilt) is consumed.

Ecosystem services analysis calculates the global yield of the Earth's biosphere to humans as a whole. This is said to be greater in size than the entire human economy. However, it is more than just yield, but also the natural processes that increase biodiversity and conserve habitat which result in the total value of these services. "Yield" of ecological commodities like wood or water, useful to humans, is only a part of it.

Very often an ecological yield in one place offsets an ecological load in another. Greenhouse gas released in one place, for instance, is fairly evenly distributed in the atmosphere, and so greenhouse gas control can be achieved by creating a carbon sink literally anywhere else.

Fishing in Ethiopia

Ethiopia's fisheries are entirely freshwater, in its many lakes, rivers, and reservoirs, as it has no marine coastline. Fishing contributed less than 1 percent of the gross domestic product in 1987. A study reported that 15,389 tonnes were caught in 2001, only 30% of an estimated potential of 51,481 tonnes.Fresh fish are consumed in the vicinity of the Great Rift Valley lakes. Outside these areas, the domestic market for fish is small. Two factors account for this low level of local fish consumption. First, fish has not been integrated into the diet of most of the population. Second, because of religious influences on consumption patterns, the demand for fish is only seasonal. During Lent, for example, Christians who abstain from eating meat, milk, and eggs consume fish.Although the Second Five-Year Agricultural Development Plan (2001-2005) laid down a number of targets to improve the yield of Ethiopia's fisheries, a number of problems remain to be overcome. Federal and state laws regarding commercial fishing did not exist until 2002/2003. This has led to localized overfishing. Some commercially important species are already suffering from overexploitation, including Nile perch in Lake Chamo, and tilapia in Lakes Awasa and Zway.The largest fishery is in Lake Tana, the country's largest lake.

Large marine ecosystem

Large marine ecosystems (LMEs) are regions of the world's oceans, encompassing coastal areas from river basins and estuaries to the seaward boundaries of continental shelves and the outer margins of the major ocean current systems. They are relatively large regions on the order of 200,000 km² or greater, characterized by distinct bathymetry, hydrography, productivity, and trophically dependent populations. Productivity in LME protected areas is generally higher than in the open ocean.

The system of LMEs has been developed by the US National Oceanic and Atmospheric Administration (NOAA) to identify areas of the oceans for conservation purposes. The objective is to use the LME concept as a tool for enabling ecosystem-based management to provide a collaborative approach to management of resources within ecologically-bounded transnational areas. This will be done in an international context and consistent with customary international law as reflected in 1982 UN Convention on the Law of the Sea.Although the LMEs cover mostly the continental margins and not the deep oceans and oceanic islands, the 66 LMEs produce about 80% of global annual marine fishery biomass. In addition, LMEs contribute $12.6 trillion in goods and services each year to the global economy. Due to their close proximity to developed coastlines, LMEs are in danger of ocean pollution, overexploitation, and coastal habitat alteration. NOAA has conducted studies of principal driving forces affecting changes in biomass yields for 33 of the 66 LMEs, which have been peer-reviewed and published in ten volumes.LME-based conservation is based on recognition that the world’s coastal ocean waters are degraded by unsustainable fishing practices, habitat degradation, eutrophication, toxic pollution, aerosol contamination, and emerging diseases, and that positive actions to mitigate these threats require coordinated actions by governments and civil society to recover depleted fish populations, restore degraded habitats and reduce coastal pollution. Five modules are considered when assessing LMEs: productivity, fish and fisheries, pollution and ecosystem health, socioeconomics, and governance. Periodically assessing the state of each module within a marine LME is encouraged to ensure maintained health of the ecosystem and future benefit to managing governments.

Manilkara

"Sapota" redirects here. This can also specifically refer to the Sapodilla (M. zapodilla).

Manilkara is a genus of trees in the family Sapotaceae. They are widespread in tropical and semitropical locations, in Africa, Madagascar, Asia, Australia, and Latin America, as well as various islands in the Pacific and in the Caribbean. A close relative is the genus Pouteria.

Trees of this genus yield edible fruit, useful wood, and latex. The best-known species are M. bidentata (balatá), M. chicle (chicle) and M. zapota (sapodilla). M. hexandra is the floral emblem of Prachuap Khiri Khan Province in Thailand, where it is known as rayan. M. obovata shares the vernacular name of African pear with another completely different species, Dacryodes edulis, and neither should be confused with Baillonella toxisperma, known by the very similar name, African pearwood.

The generic name, Manilkara, is derived from manil-kara, a vernacular name for M. kauki in Malayalam.Manilkara trees are often significant, or even dominant species in their native ecosystems, such as East Deccan dry evergreen forests, Central American premontane tropical wet forests, or together with Cynometra, in the Arabuko Sokoke National Park.

Manilkara fruit are an important food item for various frugivores, in particular birds. The red fruit bat (Stenoderma rufum) is the primary – and possibly the only – seed disperser of M. bidentata in parts of the Caribbean. Tuckerella xiamenensis, a species of peacock mite, was described from a sapodilla tree.

Several species are endangered due to overexploitation and habitat destruction. M. gonavensis of Haiti and M. spectabilis of Costa Rica are almost extinct.

Mastodon

Mastodons (Greek: μαστός "breast" and ὀδούς, "tooth") are any species of extinct proboscideans in the genus Mammut (family Mammutidae), distantly related to elephants, that inhabited North and Central America during the late Miocene or late Pliocene up to their extinction at the end of the Pleistocene 10,000 to 11,000 years ago. Mastodons lived in herds and were predominantly forest-dwelling animals that fed on a mixed diet obtained by browsing and grazing with a seasonal preference for browsing, similar to living elephants.

M. americanum, the American mastodon, and M. pacificus, the Pacific mastodon, are the youngest and best-known species of the genus. Mastodons disappeared from North America as part of a mass extinction of most of the Pleistocene megafauna, widely believed to have been caused by overexploitation by Clovis hunters.

Micropholis

For the prehistoric amphibian genus, see Micropholis (amphibian). The brittle star genus described as Micropholis has been renamed Microphiopholis.

Micropholis is group of trees in the family Sapotaceae, described as a genus in 1891.These trees are native to tropical South America, Mesoamerica, and the West Indies. Most are locally known as "cafetos", literally meaning "coffee plants". But while both Micropholis and the coffeeplant genus Coffea are asterids, the present genus is part of the Ericales – a quite basal asterid lineage –, while Coffea belongs to the more advanced Gentianales.

They are valued for their wood, which is used as timber, for construction and as firewood; many species are threatened by overexploitation and habitat destruction. Also, they are often used as part of catuaba, a decoction from various tree's bark claimed to have aphrodisiac and stimulant properties.

Caimitillo verde (M. garciniifolia) is an important food source of the nearly-extinct Puerto Rican amazon bird (Amazona vittata).

Species

Overlogging

Overlogging is a kind of overexploitation caused by legal or illegal logging activities that lead to unsustainable or irrecoverable deforestation and permanent habitat destruction for forest wildlife. Overlogging is often associated with attempts at reducing the "third world debt" but is not restricted to developing countries. With the developed world's growing demand for pulp and paper, especially - but not restricted to - for disposable tissues, overlogging is an imminent threat to Earth's forests everywhere.

Tropical timber

Tropical timber may refer to any type of timber or wood that grows in tropical rainforests and tropical and subtropical moist broadleaf forests and is harvested there. Typical examples of worldwide industrial significance include the hardwoods

Mahogany

Teak

Ebony

Rosewood

Narra

Chloroxylonamong many others.

Overexploitation of those woods has led to widespread deforestation in the tropics. The intergovernmental organization International Tropical Timber Organization is concerned with conservation of the habitats of tropical timber trees.

Water resources management in Syria

Water resources management in Syria is confronted with numerous challenges. First, all of the country's major rivers are shared with neighboring countries, and Syria depends to a large extent on the inflow of water from Turkey through the Euphrates and its tributaries. Second, high population growth and urbanisation increase the pressure on water resources, resulting in localized groundwater depletion and pollution, for example in the Ghouta near Damascus. Third, there is no legal framework for integrated water resources management. Finally, the institutions in charge of water resources management are weak, being both highly centralized and fragmented between sectors, and they often lack the power to enforce regulations. Water resources policies have been focused on the construction of dams, the development of irrigated agriculture and occasional interbasin transfers, such as a pipeline to supply drinking water to Aleppo from the Euphrates. There are 165 dams in Syria with a total storage capacity of 19.6 km³. Demand management through metering, higher tariffs, more efficient irrigation technologies and the reduction of non-revenue water in drinking water supply has received less emphasis than supply management. The government implements a large program for the construction of wastewater treatment plants including the use of reclaimed water for irrigation.

Wildlife conservation

Wildlife conservation is the practice of protecting wild species and their habitats in order to prevent species from going extinct. Major threats to wildlife include habitat destruction/degradation/fragmentation, overexploitation, poaching, hunting, pollution and climate change. The IUCN estimates that 27,000 species of the ones assessed are at risk for extinction. Expanding to all existing species, a 2019 UN report on biodiversity put this estimate even higher at a million species. It's also being acknowledged that an increasing number of ecosystems on Earth containing endangered species are disappearing. To address these issues, there have been both national and international governmental efforts to preserve Earth's wildlife. Prominent conservation agreements include the 1973 Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) and the 1992 Convention on Biological Diversity (CBD). There are also numerous nongovernmental organizations (NGO's) dedicated to conservation such as the Nature Conservancy, World Wildlife Fund, and Conservation International.

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