Уничтожение и деградация естественных сред обитания.

Process by which a natural habitat becomes incapable of supporting its native species

Habitat destruction (also termed habitat loss and habitat reduction) occurs when a natural habitat is no longer able to support its native species. The organisms once living there have either moved to elsewhere or are dead, leading to a decrease in biodiversity and species numbers. Habitat destruction is in fact the leading cause of biodiversity loss and species extinction worldwide. Humans contribute to habitat destruction through the use of natural resources, agriculture, industrial production and urbanization (urban sprawl). Other activities include mining, logging and trawling. Environmental factors can contribute to habitat destruction more indirectly. Geological processes, climate change,

Biodiversity hotspots are chiefly tropical regions that feature high concentrations of endemic species and, when all hotspots are combined, may contain over half of the world's terrestrial species. These hotspots are suffering from habitat loss and destruction. Most of the natural habitat on islands and in areas of high human population density has already been destroyed (WRI, 2003). Islands suffering extreme habitat destruction include New Zealand, Madagascar, the Philippines, and Japan. South and East Asia—especially China, India, Malaysia, Indonesia, and Japan—and many areas in West Africa have extremely dense human populations that allow little room for natural habitat. Marine areas close to highly populated coastal cities also face degradation of their coral reefs or other marine habitat. Forest City, a township in southern Malaysia built on Environmentally Sensitive Area (ESA) Rank 1 wetland is one such example, with irreversible reclamation proceeding prior to environmental impact assessment and approvals. Other such areas include the eastern coasts of Asia and Africa, northern coasts of South America, and the Caribbean Sea and its associated islands. Only 15% of land area remains unmodified by human activities in all of Europe.

Tropical rainforests have received most of the attention concerning the destruction of habitat. From the approximately 16 million square kilometers of tropical rainforest habitat that originally existed worldwide, less than 9 million square kilometers remain today. Other forest ecosystems have suffered as much or more destruction as tropical rainforests. Deforestation for farming and logging have severely disturbed at least 94% of temperate broadleaf forests; many old growth forest stands have lost more than 98% of their previous area because of human activities. But included in that 10–20% of land is the approximately 9 million square kilometers of seasonally dry lands that humans have converted to deserts through the process of desertification. Wetlands and marine areas have endured high levels of habitat destruction. More than 50% of wetlands in the U. S. have been destroyed in just the last 200 years. In the United Kingdom, there has been an increase in demand for coastal housing and tourism which has caused a decline in marine habitats over the last 60 years. The rising sea levels and temperatures have caused soil erosion, coastal flooding, and loss of quality in the UK marine ecosystem. About one fifth (20%) of marine coastal areas have been highly modified by humans. One fifth of coral reefs have also been destroyed, and another fifth has been severely degraded by overfishing, pollution, and invasive species; 90% of the Philippines' coral reefs alone have been destroyed. Finally, over 35% of the mangrove ecosystems worldwide have been destroyed.]] Habitat destruction through natural processes such as volcanism, fire, and climate change is well documented in the fossil record. The boom in human population and migration of people into such species rich regions are making conservation efforts not only more urgent but also more likely to conflict with local human interests. According to the Geist and Lambin (2002) study, the underlying driving forces were prioritized as follows (with the percent of the 152 cases the factor played a significant role in): economic factors (81%), institutional or policy factors (78%), technological factors (70%), cultural or socio political factors (66%), and demographic factors (61%). The main economic factors included commercialization and growth of timber markets (68%), which are driven by national and international demands; urban industrial growth (38%); low domestic costs for land, labor, fuel, and timber (32%); and increases in product prices mainly for cash crops (25%). Institutional and policy factors included formal pro deforestation policies on land development (40%), economic growth including colonization and infrastructure improvement (34%), and subsidies for land based activities (26%); property rights and land tenure insecurity (44%); and policy failures such as corruption, lawlessness, or mismanagement (42%). The main technological factor was the poor application of technology in the wood industry (45%), which leads to wasteful logging practices. Within the broad category of cultural and sociopolitical factors are public attitudes and values (63%), individual/household behavior (53%), public unconcern toward forest environments (43%), missing basic values (36%), and unconcern by individuals (32%). Demographic factors were the in migration of colonizing settlers into sparsely populated forest areas (38%) and growing population density—a result of the first factor—in those areas (25%).

Geist and Lambin (2002) assessed 152 case studies of net losses of tropical forest cover to determine any patterns in the proximate and underlying causes of tropical deforestation. Their results, yielded as percentages of the case studies in which each parameter was a significant factor, provide a quantitative prioritization of which proximate and underlying causes were the most significant. The proximate causes were clustered into broad categories of agricultural expansion (96%), infrastructure expansion (72%), and wood extraction (67%). Therefore, according to this study, forest conversion to agriculture is the main land use change responsible for tropical deforestation. The specific categories reveal further insight into the specific causes of tropical deforestation: transport extension (64%), commercial wood extraction (52%), permanent cultivation (48%), cattle ranching (46%), shifting (slash and burn) cultivation (41%), subsistence agriculture (40%), and fuel wood extraction for domestic use (28%). One result is that shifting cultivation is not the primary cause of deforestation in all world regions, while transport extension (including the construction of new roads) is the largest single proximate factor responsible for deforestation. Conversion to "trivial" standardized ecosystems (e. g., monoculture following deforestation) effectively destroys habitat for the more diverse species. Even the simplest forms of agriculture affect diversity – through clearing or draining the land, discouraging weeds and pests, and encouraging just a limited set of domesticated plant and animal species.

Climate change contributes to destruction of some habitats, endangering various species. For example:

Climate change causes rising sea levels which will threaten natural habitats and species globally. Melting sea ice destroys habitat for some species. For example, the decline of sea ice in the Arctic has been accelerating during the early twenty‐first century, with a decline rate of 4.7% per decade (it has declined over 50% since the first satellite records). One well known example of a species affected is the polar bear, whose habitat in the Artic is threatened. Algae can also be affected when it grows on the underside of sea ice. Warm water coral reefs are very sensitive to global warming and ocean acidification. Coral reefs provide a habitat for thousands of species. They provide ecosystem services such as coastal protection and food. But 70–90% of today's warm water coral reefs will disappear even if warming is kept to For example, Caribbean coral reefswhich are biodiversity hotspotswill be lost within the century if global warming continues at the current rate.

When a habitat is destroyed, the carrying capacity for indigenous plants, animals, and other organisms is reduced so that populations decline, sometimes up to the level of extinction. Habitat loss is perhaps the greatest threat to organisms and biodiversity. Temple (1986) found that 82% of endangered bird species were significantly threatened by habitat loss. Most amphibian species are also threatened by native habitat loss, and some species are now only breeding in modified habitat. Endemic organisms with limited ranges are most affected by habitat destruction, mainly because these organisms are not found anywhere else in the world, and thus have less chance of recovering. Many endemic organisms have very specific requirements for their survival that can only be found within a certain ecosystem, resulting in their extinction. Extinction may also take place very long after the destruction of habitat, a phenomenon known as extinction debt. Habitat destruction can also decrease the range of certain organism populations. This can result in the reduction of genetic diversity and perhaps the production of infertile youths, as these organisms would have a higher possibility of mating with related organisms within their population, or different species. One of the most famous examples is the impact upon China's giant panda, once found in many areas of Sichuan. Now it is only found in fragmented and isolated regions in the southwest of the country, as a result of widespread deforestation in the 20th century. As habitat destruction of an area occurs, the species diversity offsets from a combination of habitat generalists and specialists to a population primarily consisting of generalist species. Habitat destruction leading to climate change offsets the balance of species keeping up with the extinction threshold leading to a higher likelihood of extinction. Habitat loss is one of the main environmental causes of the decline of biodiversity on local, regional, and global scales. Many believe that habitat fragmentation is also a threat to biodiversity however some believe that it is secondary to habitat loss. The reduction of the amount of habitat available results in specific landscapes that are made of isolated patches of suitable habitat throughout a hostile environment/matrix. This process is generally due to pure habitat loss as well as fragmentation effects. Pure habitat loss refers to changes occurring in the composition of the landscape that causes a decrease in individuals. Fragmentation effects refer to an addition of effects occurring due to the habitat changes. It is observed from the worlds longest running fragmentation experiment over 35 years that habitat fragmentation has caused a decrease in biodiversity from 13% to 75%.

Habitat destruction can vastly increase an area's vulnerability to natural disasters like flood and drought, crop failure, spread of disease, and water contamination. Eliminating swamps—the habitat of pests such as mosquitoes—has contributed to the prevention of diseases such as malaria. Completely depriving an infectious agent (such as a virus) of its habitat—by vaccination, for example—can result in eradicating that infectious agent. Agricultural land can suffer from the destruction of the surrounding landscape. Over the past 50 years, the destruction of habitat surrounding agricultural land has degraded approximately 40% of agricultural land worldwide via erosion, salinization, compaction, nutrient depletion, pollution, and urbanization. Probably the most profound impact that habitat destruction has on people is the loss of many valuable ecosystem services. Habitat destruction has altered nitrogen, phosphorus, sulfur, and carbon cycles, which has increased the frequency and severity of acid rain, algal blooms, and fish kills in rivers and oceans and contributed tremendously to global climate change. waste treatment (i. e., the breaking down and immobilization of toxic pollutants), and nutrient recycling of sewage or agricultural runoff. Loss of biodiversity also means that humans are losing animals that could have served as biological control agents and plants that could potentially provide higher yielding crop varieties, pharmaceutical drugs to cure existing or future diseases (such as cancer), and new resistant crop varieties for agricultural species susceptible to pesticide resistant insects or virulent strains of fungi, viruses, and bacteria. In the past, continually moving to new land and soils provided a boost in food production to meet the global food demand. That easy fix will no longer be available, however, as more than 98% of all land suitable for agriculture is already in use or degraded beyond repair. The impending global food crisis will be a major source of habitat destruction. Commercial farmers are going to become desperate to produce more food from the same amount of land, so they will use more fertilizers and show less concern for the environment to meet the market demand. Others will seek out new land or will convert other land uses to agriculture. Agricultural intensification will become widespread at the cost of the environment and its inhabitants. Species will be pushed out of their habitat either directly by habitat destruction or indirectly by fragmentation, degradation, or pollution. Any efforts to protect the world's remaining natural habitat and biodiversity will compete directly with humans' growing demand for natural resources, especially new agricultural lands. Tropical deforestation: In most cases of tropical deforestation, three to four underlying causes are driving two to three proximate causes. Preventing an area from losing its specialist species to generalist invasive species depends on the extent of the habitat destruction that has already taken place. In areas where the habitat is relatively undisturbed, halting further habitat destruction may be enough. Education of the general public is possibly the best way to prevent further human habitat destruction. Changing the dull creep of environmental impacts from being viewed as acceptable to being seen a reason for change to more sustainable practices. Habitat restoration can also take place through the following processes; extending habitats or repairing habitats. Extending habitats aims to counteract habitat loss and fragmentation whereas repairing habitats counteracts degradation. Corridors are also known to reduce the negative impacts of habitat destruction. conservation areas, and addressing climate change.