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53-713: Management of the reserve is governed by the Tanzanian Board of Trustees of Marine Parks and Reserves which is the custodian and overseer of the establishment and management of the Marine Protected Reserves in Tanzania. The Dar es Salaam Marine Reserves were first established under the Fisheries Act of 1970 and in 1998 were transferred to the Marine Parks and Reserves [1] (MPRs), Act No. 29 of 1994. [2] . Visits to

106-457: A renewable resource to the point of diminishing returns . Continued overexploitation can lead to the destruction of the resource, as it will be unable to replenish. The term applies to natural resources such as water aquifers , grazing pastures and forests , wild medicinal plants , fish stocks and other wildlife . In ecology , overexploitation describes one of the five main activities threatening global biodiversity . Ecologists use

159-554: A cautionary tale about the delicate balance between human activity and biodiversity and highlights the potential consequences of over-hunting and habitat destruction. A second wave of extinctions occurred later with European settlement. This period marked significant ecological disruption, largely due to the introduction of new species and land-use changes. European settlers brought with them animals such as rats, cats, and stoats, which preyed upon native birds and other wildlife. Additionally, deforestation for agriculture significantly altered

212-617: A few remain to the north of Dar es Salaam . In contrast, the Dar es Salaam Marine Reserve system is made up of nine tiny, uninhabited islands, six of which are known to have colonies of coconut crabs ( Mbudya , Bongoyo , Pangavini , Kendwa , Sinda Island ). Bongoyo Island had the largest specimens of the crabs in the country. This Dar es Salaam Region location article is a stub . You can help Misplaced Pages by expanding it . Over-exploitation Overexploitation , also called overharvesting or ecological overshoot , refers to harvesting

265-410: 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,

318-434: A food shortage and have been observed feeding on sea otters, again reducing their numbers. Flora Flora ( pl. : floras or florae ) is all the plant life present in a particular region or time, generally the naturally occurring ( indigenous ) native plants. The corresponding term for animals is fauna , and for fungi , it is funga . Sometimes bacteria and fungi are also referred to as flora as in

371-504: A historic era as in fossil flora . Lastly, floras may be subdivided by special environments: The flora of a particular area or time period can be documented in a publication also known as a " flora " (often capitalized as "Flora" to distinguish the two meanings when they might be confused). Floras may require specialist botanical knowledge to use with any effectiveness. Traditionally they are books , but some are now published on CD-ROM or websites . Simon Paulli 's Flora Danica of 1648

424-603: 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. 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

477-438: A lack of fear toward predators, including humans, making it exceptionally vulnerable to hunting. The dodo's naivety and the absence of natural defenses against human hunters and introduced species led to its rapid extinction. This case offers insight into how certain species, particularly those isolated on islands, can be disproportionately affected by human activities due to their evolutionary adaptations. Hunting has long been

530-406: A large scale study of fisheries that used ITQs, and ones that did not, provided strong evidence that ITQs help prevent collapses and restore fisheries that appear to be in decline. 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 do not recharge). Overexploitation occurs if

583-479: A major source of aquifer depletion. 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 . These debates usually centre around agriculture and suburban water usage but generation of electricity from nuclear energy or coal and tar sands mining

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636-587: A mere 200 years after the first human settlements, ten species of the giant moa birds were driven to extinction by the Māori . This rapid extinction underscores the significant impact humans can have on native wildlife, especially in isolated ecosystems like New Zealand. The Māori, relying on the moa as a primary food source and for resources such as feathers and bones, hunted these birds extensively. The moa's inability to fly and their size, which made them easier targets, contributed to their rapid decline. This event serves as

689-407: A staggering scale of resource extraction that ultimately contributed to its extinction. This instance underscores how cultural traditions and their associated demands can sometimes precipitate the overexploitation of a species to the brink of extinction. Similarly, the story of the dodo bird from Mauritius provides another clear example of overexploitation. The dodo, a flightless bird, exhibited

742-494: A vital human activity for survival, providing food, clothing, and tools. However, the history of hunting also includes episodes of overexploitation, particularly in the form of overhunting. The overkill hypothesis , which addresses the Quaternary extinction events, explains the relatively rapid extinction of megafauna . This hypothesis suggests that these extinctions were closely linked to human migration and population growth. One of

795-466: 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

848-578: A work cataloguing such vegetation. Moreover, "Flora" was used to refer to the flowers of an artificial garden in the seventeenth century. The distinction between vegetation (the general appearance of a community) and flora (the taxonomic composition of a community) was first made by Jules Thurmann (1849). Prior to this, the two terms were used interchangeably. Plants are grouped into floras based on region ( floristic regions ), period, special environment, or climate. Regions can be distinct habitats like mountain vs. flatland. Floras can mean plant life of

901-583: 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

954-645: Is also water resource intensive. A modified Hubbert curve applies to any resource that can be harvested faster than it can be replaced. 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 . 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

1007-492: 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. A good example of this are island snails, such as the Hawaiian Achatinella and

1060-465: 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". 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". However, overexploitation can be sustainable. When

1113-399: Is common to the greatest number has the least care bestowed upon it", as well as to Hobbes and his Leviathan . 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

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1166-488: Is drug discovery and the availability of medicinal resources. A significant proportion of drugs are natural products derived, directly or indirectly, from biological sources. Marine ecosystems are of particular interest in this regard. However, unregulated and inappropriate bioprospecting could potentially lead to overexploitation, ecosystem degradation and loss of biodiversity . Species from all groups of fauna and flora are affected by overexploitation. This phenomenon

1219-446: 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

1272-438: Is not an activity limited to humans. Introduced predators and herbivores, for example, can overexploit native flora and fauna . The concern about overexploitation, while relatively recent in the annals of modern environmental awareness, traces back to ancient practices embedded in human history. Contrary to the notion that overexploitation is an exclusively contemporary issue, the phenomenon has been documented for millennia and

1325-498: Is not bound by taxonomy; it spans across mammals, birds, fish, insects, and plants alike. Animals are hunted for their fur, tusks, or meat, while plants are harvested for medicinal purposes, timber, or ornamental uses. This unsustainable practice disrupts ecosystems, threatening biodiversity and leading to the potential extinction of vulnerable species. All living organisms require resources to survive. Overexploitation of these resources for protracted periods can deplete natural stocks to

1378-466: Is not limited to human activities alone. Historical evidence reveals that various cultures and societies have engaged in practices leading to the overuse of natural resources, sometimes with drastic consequences. One poignant example can be found in the ceremonial cloaks of Hawaiian kings , which were adorned with the feathers of the now-extinct mamo bird. Crafting a single cloak required the feathers of approximately 70,000 adult mamo birds, illustrating

1431-599: Is probably the first book titled "Flora" to refer to the plant world of a certain region. It mainly describes medicinal plants growing in Denmark. The Flora Sinensis by the Polish Jesuit Michał Boym is another early example of a book titled "Flora". However, despite its title it covered not only plants but also some animals of the region, that is China and India. A published flora often contains diagnostic keys. Often these are dichotomous keys , which require

1484-455: Is reduced until the stock biomass returns to the optimal biomass. At this point, harvesting can be resumed near the maximum sustainable yield. 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,

1537-433: 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,

1590-518: 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. 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. This decline has been called

1643-532: The bushmeat crisis . 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 . The Convention for International Trade in Endangered Species of Wild Fauna and Flora, or CITES

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1696-496: The exploitation of many species beyond sustainable levels. 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 . Overexploitation often occurs rapidly as markets open, utilising previously untapped resources, or locally used species. Today, overexploitation and misuse of natural resources

1749-444: The 1970s and 1980s, leading to their abrupt collapse in 1992. Even though fishing has ceased, the cod stocks have failed to recover. The absence of cod as the apex predator in many areas has led to trophic cascades . 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. These depleted fisheries can often recover if fishing pressure

1802-526: The Commons". 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. 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

1855-468: The French Polynesian Partula . Achatinelline snails have 15 species listed as extinct and 24 critically endangered while 60 species of partulidae are considered extinct with 14 listed as critically endangered. The WCMC have attributed over-collecting and very low lifetime fecundity for the extreme vulnerability exhibited among these species. As another example, when the humble hedgehog

1908-435: 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. In the course of his essay, Hardin develops

1961-431: The consequent declining timber harvests. Overexploitation is one of the main threats to global biodiversity . Other threats include pollution , introduced and invasive species, habitat fragmentation , habitat destruction , uncontrolled hybridization , climate change , ocean acidification and the driver behind many of these, human overpopulation . One of the key health issues associated with biodiversity

2014-505: 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. In 1968, the journal Science published an article by Garrett Hardin entitled "The Tragedy of

2067-602: The habitats of many endemic species. These combined factors accelerated the decline of New Zealand's unique biodiversity, leading to the extinction of several more species. The European settlement period serves as a poignant example of how human activities can drastically impact natural ecosystems. 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 , eco-development , and deep ecology . Overexploitation does not necessarily lead to

2120-467: The loss of the kelp caused other cascade effects of secondary extinctions. 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

2173-409: 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. It is possible to fish the stock down further to, say, 15% of

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2226-619: The most compelling pieces of evidence supporting this theory is that approximately 80% of North American large mammal species disappeared within just approximately a thousand years of humans arriving in the Western Hemisphere . This rapid disappearance indicates a significant impact of human activity on these species, underscoring the profound influence humans have had on their environment throughout history. The fastest-ever recorded extinction of megafauna occurred in New Zealand . By 1500 AD,

2279-484: 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. One of the sea otters’ primary food sources

2332-413: The point where they are unable to recover within a short time frame. Humans have always harvested food and other resources they need to survive. Human populations, historically, were small, and methods of collection were 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

2385-443: 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

2438-442: The reserve area (especially Bongoyo and Mbudya) are a popular daytrip for both tourists and Tanzanian residents alike, the islands serving as a location for a variety of leisure activities, including snorkelling, sunbathing and hiking. However, over recent years unregulated tourist activities has led to degradation within the reserves. The nearby fishing communities of Kunduchi, Unonio, and Msasani all appear to be heavily dependent on

2491-461: The resources in the reserves [3] and resource over-exploitation is an increasing concern with local fishermen attributing a decline in fish catches over recent years to the use of small mesh nets and dynamite fishing . A decrease in the abundance of fish and coral health, and an increased amount of bleached and broken coral has been noted by divers. On Tanzania's mainland, it appears that there are hardly any populations left, while it's likely that

2544-465: The term to describe populations that are harvested at an unsustainable rate, 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. The term

2597-500: The terms gut flora or skin flora . The word "flora" comes from the Latin name of Flora , the goddess of plants , flowers , and fertility in Roman mythology . The technical term "flora" is then derived from a metonymy of this goddess at the end of the sixteenth century. It was first used in poetry to denote the natural vegetation of an area, but soon also assumed the meaning of

2650-507: 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". 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

2703-449: The total) have been subject to overexploitation, including: 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

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2756-466: 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%. Where there is substantial human migration, civil unrest, or war, controls may no longer exist. With civil unrest, for example in

2809-469: 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. Overall, 50 bird species that have become extinct since 1500 (approximately 40% of

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