DEFORESTATION
Deforestation is the clearance of naturally occurring forests by logging and burning.
Deforestation occurs for many reasons: trees or derived charcoal are used as, or sold, for fuel or as a commodity, while cleared land is used as pasture for livestock, plantations of commodities, and settlements. The removal of trees without sufficient reforestation has resulted in damage to habitat, biodiversity loss and aridity. It has adverse impacts on biosequestration of atmospheric carbon dioxide. Deforested regions typically incur significant adverse soil erosion and frequently degrade into wasteland.
Disregard or ignorance of intrinsic value, lack of ascribed value, lax forest management and deficient environmental law are some of the factors that allow deforestation to occur on a large scale. In many countries, deforestation is an ongoing issue that is causing extinction, changes to climatic conditions, desertification, and displacement of indigenous people.
Among countries with a per capita GDP of at least US$4,600, net deforestation rates have ceased to increase.
Deforestation occurs for many reasons: trees or derived charcoal are used as, or sold, for fuel or as a commodity, while cleared land is used as pasture for livestock, plantations of commodities, and settlements. The removal of trees without sufficient reforestation has resulted in damage to habitat, biodiversity loss and aridity. It has adverse impacts on biosequestration of atmospheric carbon dioxide. Deforested regions typically incur significant adverse soil erosion and frequently degrade into wasteland.
Disregard or ignorance of intrinsic value, lack of ascribed value, lax forest management and deficient environmental law are some of the factors that allow deforestation to occur on a large scale. In many countries, deforestation is an ongoing issue that is causing extinction, changes to climatic conditions, desertification, and displacement of indigenous people.
Among countries with a per capita GDP of at least US$4,600, net deforestation rates have ceased to increase.
CAUSES OF DEFORESTATION
here are many root causes of contemporary deforestation, including corruption of government institutions, the inequitable distribution of wealth and power, population growth and overpopulation, and urbanization.Globalization is often viewed as another root cause of deforestation, though there are cases in which the impacts of globalization (new flows of labor, capital, commodities, and ideas) have promoted localized forest recovery.
In 2000 the United Nations Food and Agriculture Organization (FAO) found that "the role of population dynamics in a local setting may vary from decisive to negligible," and that deforestation can result from "a combination of population pressure and stagnating economic, social and technological conditions."
According to the United Nations Framework Convention on Climate Change (UNFCCC) secretariat, the overwhelming direct cause of deforestation is agriculture. Subsistence farming is responsible for 48% of deforestation; commercial agriculture is responsible for 32% of deforestation; logging is responsible for 14% of deforestation and fuel wood removals make up 5% of deforestation.
The degradation of forest ecosystems has also been traced to economic incentives that make forest conversion appear more profitable than forest conservation.[14] Many important forest functions have no markets, and hence, no economic value that is readily apparent to the forests' owners or the communities that rely on forests for their well-being.[14] From the perspective of the developing world, the benefits of forest as carbon sinks or biodiversity reserves go primarily to richer developed nations and there is insufficient compensation for these services. Developing countries feel that some countries in the developed world, such as the United States of America, cut down their forests centuries ago and benefited greatly from this deforestation, and that it is hypocritical to deny developing countries the same opportunities: that the poor shouldn't have to bear the cost of preservation when the rich created the problem.
Experts do not agree on whether industrial logging is an important contributor to global deforestation. Similarly, there is no consensus on whether poverty is important in deforestation. Some argue that poor people are more likely to clear forest because they have no alternatives, others that the poor lack the ability to pay for the materials and labour needed to clear forest. Claims that population growth drives deforestation have been disputed;[16] one study found that population increases due to high fertility rates were a primary driver of tropical deforestation in only 8% of cases.
Some commentators have noted a shift in the drivers of deforestation over the past 30 years.Whereas deforestation was primarily driven by subsistence activities and government-sponsored development projects like transmigration in countries like Indonesia and colonization in Latin America, India, Java etc during late 19th century and the earlier half of the 20th century. By the 1990s the majority of deforestation was caused by industrial factors, including extractive industries, large-scale cattle ranching, and extensive agriculture.
In 2000 the United Nations Food and Agriculture Organization (FAO) found that "the role of population dynamics in a local setting may vary from decisive to negligible," and that deforestation can result from "a combination of population pressure and stagnating economic, social and technological conditions."
According to the United Nations Framework Convention on Climate Change (UNFCCC) secretariat, the overwhelming direct cause of deforestation is agriculture. Subsistence farming is responsible for 48% of deforestation; commercial agriculture is responsible for 32% of deforestation; logging is responsible for 14% of deforestation and fuel wood removals make up 5% of deforestation.
The degradation of forest ecosystems has also been traced to economic incentives that make forest conversion appear more profitable than forest conservation.[14] Many important forest functions have no markets, and hence, no economic value that is readily apparent to the forests' owners or the communities that rely on forests for their well-being.[14] From the perspective of the developing world, the benefits of forest as carbon sinks or biodiversity reserves go primarily to richer developed nations and there is insufficient compensation for these services. Developing countries feel that some countries in the developed world, such as the United States of America, cut down their forests centuries ago and benefited greatly from this deforestation, and that it is hypocritical to deny developing countries the same opportunities: that the poor shouldn't have to bear the cost of preservation when the rich created the problem.
Experts do not agree on whether industrial logging is an important contributor to global deforestation. Similarly, there is no consensus on whether poverty is important in deforestation. Some argue that poor people are more likely to clear forest because they have no alternatives, others that the poor lack the ability to pay for the materials and labour needed to clear forest. Claims that population growth drives deforestation have been disputed;[16] one study found that population increases due to high fertility rates were a primary driver of tropical deforestation in only 8% of cases.
Some commentators have noted a shift in the drivers of deforestation over the past 30 years.Whereas deforestation was primarily driven by subsistence activities and government-sponsored development projects like transmigration in countries like Indonesia and colonization in Latin America, India, Java etc during late 19th century and the earlier half of the 20th century. By the 1990s the majority of deforestation was caused by industrial factors, including extractive industries, large-scale cattle ranching, and extensive agriculture.
CORAL BLEACHING
Coral bleaching is the whitening of corals, due to stress-induced expulsion or death of symbiotic, algae-like protozoa, or due to the loss of pigmentation within the protozoa. The corals that form the structure of the great reef ecosystems of tropical seas depend upon a symbiotic relationship with unicellular flagellate protozoa, called zooxanthellae, that are photosynthetic and live within their tissues. Zooxanthellae give coral its coloration, with the specific color depending on the particular clade. Under stress, corals may expel their zooxanthellae, which leads to a lighter or completely white appearance, hence the term "bleached".
Once bleaching begins, it tends to continue even without continuing stress. If the coral colony survives the stress period, zooxanthellae often require weeks to months to return to normal density. The new residents may be of a different species. Some species of zooxanthellae and corals are more resistant to stress than other species.
Once bleaching begins, it tends to continue even without continuing stress. If the coral colony survives the stress period, zooxanthellae often require weeks to months to return to normal density. The new residents may be of a different species. Some species of zooxanthellae and corals are more resistant to stress than other species.
Causes of coral bleaching
Coral bleaching is a vivid sign of corals responding to stress, which can be induced by any of:
- increased (most commonly), or reduced water temperatures
- increased solar irradiance
- changes in water chemistry (in particular acidification)
- starvation caused by a decline in zooplankton
- increased sedimentation (due to silt runoff)
- pathogen infections
- changes in salinity
- wind
- low tide air exposure[5] Temperature change
Temperature change is the most common cause of coral bleaching.
Large coral colonies such as Porites are able to withstand extreme temperature shocks, while fragile branching corals such as table coral are far more susceptible to stress following a temperature change. Corals consistently exposed to low stress levels may be more resistant to bleaching.
Factors that influence the outcome of a bleaching event include stress-resistance which reduces bleaching, tolerance to the absence of zooxanthellae, and how quickly new coral grows to replace the dead. Due to the patchy nature of bleaching, local climatic conditions such as shade or a stream of cooler water can reduce bleaching incidence. Coral and zooxanthellae health and genetics also influence bleaching.
Monitoring reef sea surface temperature
The US National Oceanic and Atmospheric Administration (NOAA) monitors for bleaching "hot spots", areas where sea surface temperature rises 1 degree Celsius or more above the long-term monthly average. This system detected the worldwide 1998 bleaching event, that corresponded to an el nino. NOAA also uses a satellite with 50k resolution at night, which some argue covers too large a spatial area and does not detect the maximum sea surface temperatures occurring usually around noon.
Changes in ocean chemistry
Increasing ocean acidification likely exacerbates the bleaching effects of thermal stress.
Infectious disease
It was discovered in 1996 that the bleaching agent of Oculina patagonica in the Mediterranean Sea was infectious bacteria attacking the zooxanthellae. The bacteria were later identified as Vibrio shiloi. V. shiloi is infectious only during warm periods. Elevated temperature increases the virulence of V. shiloi, which then become able to adhere to abeta galactoside-containing receptor in the surface mucus of the host coral. V. shiloi then penetrates the coral's epidermis, multiplies, and produces both heat-stable and heat-sensitive toxins, which affect zooxanthellae by inhibiting photosynthesis and causing lysis.
During the summer of 2003, coral reefs in the Mediterranean Sea appeared to gain resistance to the pathogen, and further infection was not observed. The main hypothesis for the emerged resistance is the presence of symbiotic communities of protective bacteria living in the corals. The bacterial species capable of lysing V. shiloi has not been identified.
MANGROVE ECOSYSTEM
Mangroves are trees and shrubs that grow saline coastal habitats in the tropics and subtropics – mainly between latitudes 25° N and 25° S. The saline conditions tolerated by various species range from brackish water, through pure seawater (30 to 40 ppt), to water of over twice the salinity of ocean seawater, where the salt has become concentrated by evaporation (up to 90 ppt).
There are many species of trees and shrubs adapted to saline conditions. Not all are closely related, and the term "mangrove" may be used for all of them, or more narrowly only for the mangrove family of plants, the Rhizophoraceae, or even more specifically just for mangrove trees of the genus Rhizophora.
Mangroves form a characteristic saline woodland or shrubland habitat, called mangrove swamp, mangrove forest, mangrove or mangal. Mangals are found in depositional coastal environments where fine sediments (often with high organic content) collect in areas protected from high energy wave action. They occur both in estuaries and along open coastlines. Mangroves dominate three quarters of tropical coastlines.
There are many species of trees and shrubs adapted to saline conditions. Not all are closely related, and the term "mangrove" may be used for all of them, or more narrowly only for the mangrove family of plants, the Rhizophoraceae, or even more specifically just for mangrove trees of the genus Rhizophora.
Mangroves form a characteristic saline woodland or shrubland habitat, called mangrove swamp, mangrove forest, mangrove or mangal. Mangals are found in depositional coastal environments where fine sediments (often with high organic content) collect in areas protected from high energy wave action. They occur both in estuaries and along open coastlines. Mangroves dominate three quarters of tropical coastlines.
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