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Habitat destruction

    Habitat destruction is a process of land use change in which one habitat-type is removed and replaced with another habitat-type In the process of land-use change plants and animals which previously used the site are displaced or destroyed reducing biodiversity Urban Sprawl is one cause of habitat destruction Other important causes of habitat destruction include mining trawling and agriculture Habitat destruction is currently ranked as the most important cause of species extinction worldwidePimm Stuart L. and Peter Raven (2000) : Extinction by numbers Nature 403: 843-845 doi:101038/35002708 It is a process of environmental change important in evolution and conservation biology As the name implies it describes the emergence of discontinuities (fragmentation) in an organism's preferred environment (habitat) Habitat fragmentation can be caused by geological processes that slowly alter the layout of the physical environment or by human activity such as land conversion which can alter the environment on a much faster time scale The former is suspected of being one of the major causes of speciation The latter is causative in extinctions of many species
    This term or the terms "loss of habitat" and "habitat reduction" can also be used in a wider sense including loss of habitat due to other factors such as noise pollution

    See also


    Habitat Destruction
    Table of Contents:
    What is habitat destruction?How and how much does habitat destruction affect plants and animals?What animals and plants are most affected by habitat destruction?What areas have experienced the most intense habitat destruction?How much habitat has been destroyed in each type of ecosystem?What human activities directly lead to habitat destruction?What are the drivers of habitat destruction?How does habitat destruction negatively impact humans populations?What’s the outlook for habitat destruction?What can be done to reduce habitat destruction?
    What is habitat destruction?Habitat destruction is any human-induced habitat change that results in a diminishment of natural habitat This includes conversion of land to agriculture urban sprawl infrastructure development and other human-related (unnatural) changes in the physical characteristics of land Habitat degradation fragmentation and pollution are all subsets of the broader category of habitat destruction; these do not involve overt destruction of habitat yet they cause many of the same results Desertification deforestation and coral reef degradation are specific types of habitat destruction for those areas (deserts forests and coral reefs)
    How and how much does habitat destruction affect plants and animals? In the simplest terms when a habitat is destroyed the plants animals and other organisms that occupied that habitat now have no place to go, so they simply die off (Scholes and Biggs 2004) The single greatest threat to species worldwide is the loss of habitat (Barbault and Sastrapradja 1995) Temple (1986) found that 82% of endangered bird species were significantly threatened by habitat loss Habitat destruction often sugar-coated by the more acceptable phrase of “land-use change” is unquestionably the primary cause of loss of biodiversity
    What areas have experienced the most intense habitat destruction?Biodiversity hotspots are mostly 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 (Cincotta and Engelman 2000) These hotspots are suffering enormous habitat loss as each hotspot has lost at least 70% of its primary vegetation (Cincotta and Engelman 2000)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 (Primack 2006) South and east Asia—especially China India Malaysia Indonesia and Japan—and many areas in west Africa have extremely dense human populations that allow no room for natural habitat Marine areas close to highly populated coastal cities also face degradation of their coral reefs or other marine habitat These areas include the eastern coasts of Asia and Africa northern coasts of South America and the Caribbean Sea and its associated islands (Primack 2006)Areas of unsustainable agriculture and/or unstable governments which usually go hand-in-hand inevitably experience high rates of habitat destruction Central America Sub-Saharan Africa and the Amazonian tropical rainforest areas of South America are the main regions with unsustainable agricultural practices or government mismanagement (Primack 2006)Areas of high agricultural output tend to have high amounts of habitat destruction In the US less than 25% of natural vegetation remains in many parts of the East and Midwest (Stein et al 2000) Even worse only 15% of land area remains unmodified by human activities in all of Europe (Primack 2006)
    How much habitat has been destroyed in each type of ecosystem?Tropical rainforests have received most of the attention concerning the destruction of habitat and for good reason From the approximately 16 million square kilometers of tropical rainforest habitat that originally existed worldwide less than 9 million square kilometers remain today (Primack 2006) The current rate of deforestation is 160000 square kilometers per year which equates to a loss of approximately 1% of original forest habitat each year (Laurance 1999)Other forest ecosystems have suffered as much or more destruction as tropical rainforests 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 due to human activities (Primack 2006) Tropical deciduous “dry” forests are easier to clear and burn and are more suitable for agriculture and cattle ranching than tropical rainforests; consequently less than 01% of dry forests in Central America’s Pacific Coast and less than 8% in Madagascar remain from their original extents (Laurance 1999)Plains and desert areas have been degraded to a lesser extent Only 10-20% of the world’s drylands which include temperate shrublands grasslands scrub and deciduous forests have been somewhat degraded (Kauffman and Pyke 2001) 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 (Primack 2006) The tallgrass prairies of North America on the other hand have less than 3% of natural habitat remaining that has not been converted to farmland (White et al 2000)Wetlands and marine areas are definitely on the higher end of the spectrum for habitat destruction More than 50% of wetlands in the US have been destroyed in just the last 200 years (Stein et al 2000) Even worse between 60% and 70% of European wetlands have been completely destroyed (Ravenga et al 2000) About one-fifth (20%) of marine coastal areas have been highly modified by humans (Burke et al 2000) One-fifth of coral reefs have also been utterly destroyed and another fifth has been severely degraded by overfishing pollution and invasive species; 90% of the Philippines’ coral reefs alone have been destroyed (MEA 2005) Finally over 35% mangrove ecosystems worldwide have been destroyed (MEA 2005)
    What human activities directly lead to habitat destruction?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 use responsible for tropical deforestation The specific categories revealed even more 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%) The most striking result is that shifting cultivation is nowhere near the primary cause of deforestation while transport extension (including the construction of new roads) is the largest single proximate factor responsible for deforestation
    What are the drivers of habitat destruction?While the above-mentioned activities are the proximal or direct causes of habitat destruction in that they actually destroy habitat this still does not identify why humans destroy habitat The forces that cause humans to destroy habitat are known as drivers of habitat destruction Demographic economic sociopolitical scientific and technological and cultural drivers all contribute to habitat destruction (MEA 2005)Demographic drivers include the worldwide human population size; rate of population increase over time; spatial distribution of people in a given area (urban versus rural) ecosystem type and country; and the combined effects of poverty age family planning gender and education status of people in certain areas (MEA 2005) Most of the exponential human population growth worldwide is occurring in or close to biodiversity hotspots (Cincotta and Engelman 2000) This may explain why human population density accounts for 879% of the variation in numbers of threatened species across 114 countries providing indisputable evidence that people play the largest role in decreasing biodiversity (McKee et al 2003) 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 (Cincotta and Engelman 2000) The high local population density in such areas is directly correlated to the poverty status of the local people most of whom lack an education and family planning (Geist and Lambin 2002)From the Geist and Lambin (2002) study described in the previous section 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%)There are also feedbacks and interactions among the proximate and underlying causes of deforestation that can amplify the process Road construction has the largest feedback effect because it interacts with—and leads to—the establishment of new settlements and more people which causes a growth in wood (logging) and food markets (Geist and Lambin 2002) Growth in these markets in turn progresses the commercialization of agriculture and logging industries When these industries become commercialized they must become more efficient by utilizing larger or more modern machinery that often are worse on the habitat than traditional farming and logging methods Either way more land is cleared more rapidly for commercial markets This common feedback example manifests just how closely related the proximate and underlying causes are to each other
    How does habitat destruction impact human populations? Habitat destruction vastly increases an area’s vulnerability to natural disasters like flood and drought crop failure spread of disease and water contamination (MEA 2005) On the other hand a healthy ecosystem with good management practices will reduce the chance of these and other events from ever happening or will at least reduce the impacts if any do occurAgricultural land can actually 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 (MEA 2005)Humans also lose direct uses of natural habitat when habitat is destroyed Aesthetic uses such as birdwatching recreational uses like hunting and fishing and ecotourism usually rely upon virtually undisturbed habitat Many people value the complexity of the natural world and are disturbed by the loss of natural habitats and animal or plant species worldwideProbably 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 (MEA 2005) One ecosystem service whose significance is becoming more realized is climate regulation On a local scale trees provide windbreaks and shade; on a regional scale water from plant transpiration recycles rainwater and maintains constant annual rainfall; on a global scale plants (especially trees from tropical rainforests) from around the world counter the accumulation of greenhouse gases in the atmosphere by sequestering carbon dioxide through photosynthesis (Primack 2006) Other ecosystem services that are diminished or lost altogether as a result of habitat destruction include watershed management nitrogen fixation oxygen production waste treatment (ie the breaking down and immobilization of toxic pollutants) and nutrient recycling of sewage or agricultural runoff (Primack 2006)The loss of trees from the tropical rainforests alone represents a substantial diminishment of the earth’s ability to produce oxygen and use up carbon dioxide These services are becoming even more important as increasing carbon dioxide levels is one of the main contributors to global climate changeThe loss of biodiversity may not directly affect humans but the indirect effects of losing many species as well as the diversity of ecosystems in general are enormous When biodiversity is lost the environment loses many species that provide valuable and unique roles to the ecosystem The environment and all its inhabitants rely on biodiversity to recover from extreme environmental conditions When too much biodiversity is lost a catastrophic event such as an earthquake flood or volcanic eruption could cause an ecosystem to crash and humans would obviously suffer from that 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 or cancer and new resistant crop varieties for agricultural species susceptible to pesticide-resistant insects or virulent strains of fungi viruses and bacteria (Primack 2006)The negative effects of habitat destruction usually impact rural populations more directly than urban populations (MEA 2005) Across the globe poor people suffer the most when natural habitat is destroyed because less natural habitat means less natural resources per capita yet wealthier people and countries simply have to pay more to continue to receive more than their per capita share of natural resourcesAnother way to view the negative effects of habitat destruction is to look at the opportunity cost of keeping an area undisturbed In other words what are people losing out on by taking away a given habitat? A country may increase its food supply by converting forest land to row-crop agriculture but the value of the same land may be much larger when it can supply natural resources or services such as clean water timber ecotourism or flood regulation and drought control (MEA 2005)
    What’s the outlook for habitat destruction?The rapid expansion of the global human population will no doubt increase the world’s food requirement People will always need food so simple logic tells us that more people will require more food In fact as the world’s population increases dramatically agricultural output will need to increase by at least 30% and as high as 50% over the next 30 years (Tilman et al 2001) As if this is not a big enough problem in itself the world will also have to find a new solution to increasing its food output In the past continually moving to new land and soils provided enough of a boost in food production to appease the global food demand This 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 (Sanderson et al 2002)The impending global food crisis will be a major source of habitat destruction that will continue indefinitely Commercial farmers are going to become desperate to produce more food from the same amount of land so they will use more fertilizers and 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 (Tilman et al 2001)
    What can be done to reduce habitat destruction?In most cases of tropical deforestation three to four underlying causes are driving two to three proximate causes (Geist and Lambin 2002) This means that a universal policy for controlling tropical deforestation would not be able to address the unique combination of proximate and underlying causes of deforestation in each country (Geist and Lambin 2002) Before any local national or international deforestation policies are written and enforced governmental leaders must acquire a detailed understanding of the complex combination of proximate causes and underlying driving forces of deforestation in a given area or country (Geist and Lambin 2002) This concept along with many other results about tropical deforestation from the Geist and Lambin study can easily be applied habitat destruction in general Once all the appropriate research has been performed and gathered for a particular area the governmental leaders need to take action by addressing the underlying driving forces rather than just trying to regulate the proximate causesIn a broader sense governmental bodies at a local national and international scale all need to emphasize the following:(1) considering the many irreplaceable ecosystem services provided by natural habitats(2) protecting any remaining intact sections of natural habitat(3) educating the public about the importance of natural habitat and the biodiversity it provides(4) developing family planning programs in areas of rapid population growth and(5) finding other ways to increase agricultural output than simply increasing the total land in production
    Literature CitedBarbault R. and S. D. Sastrapradja 1995 Generation maintenance and loss of biodiversity Global Biodiversity Assessment Cambridge Univ Press Cambridge pp. 193–274
    Burke L., Y. Kura K. Kassem C. Ravenga M. Spalding and D. McAllister 2000 Pilot Assessment of Global Ecosystems: Coastal Ecosystems World Resources Institute Washington DC
    Cincotta RP and R. Engelman 2000 Nature's : human population density and the future of biological diversity Population Action International Washington DC
    Geist H. J., and E. E. Lambin 2002 Proximate causes and underlying driving forces of tropical deforestation BioScience 52(2): 143-150
    Kauffman J. B. and D. A. Pyke 2001 Range ecology global livestock influences In S. A. Levin (ed) Encyclopedia of Biodiversity 5: 33-52 Academic Press San Diego CA.
    Laurance W. F. 1999 Reflections on the tropical deforestation crisis Biological Conservation 91: 109-117
    McKee J. K., PW Sciulli C. D. Fooce and T. A. Waite 2003 Forecasting global biodiversity threats associated with human population growth Biological Conservation 115: 161-164
    MEA 2005 Ecosystems and Human Well-Being Millennium Ecosystem Assessment Island Press Covelo CA.
    Primack R. B. 2006 Essentials of Conservation Biology 4th Ed. Habitat destruction pages 177-188 Sinauer Associates Sunderland MA
    Ravenga C., J. Brunner N. Henninger K. Kassem and R. Payne 2000 Pilot Analysis of Global Ecosystems: Wetland Ecosystems World Resources Institute Washington DC
    Sanderson E. W., M. Jaiteh M. A. Levy K. H. Redford A. V. Wannebo and G. Woolmer 2002 The human footprint and the last of the wild Bioscience 52(10): 891-904
    Scholes R. J. and R. Biggs (eds) 2004 Ecosystem services in Southern Africa: a regional assessment The regional scale component of the Southern African Millennium Ecosystem Assessment CSIR Pretoria South Africa
    Stein B. A., L. S. Kutner and J. S. Adams (eds) 2000 Precious Heritage: The Status of Biodiversity in the United States Oxford University Press New York
    Temple S. A. 1986 The problem of avian extinctions Ornithology 3: 453-485
    Tilman D., J. Fargione B. Wolff C. D’Antonio A. Dobson R. Howarth D. Schindler W. H. Schlesinger D. Simberloff and D. Swackhamer 2001 Forecasting agriculturally driven global environmental change Science 292: 281-284
    White R. P., S. Murray and M. Rohweder 2000 Pilot Assessment of Global Ecosystems: Grassland Ecosystems World Resources Institute Washington D. C.
    WRI 2003 World Resources 2002-2004: Decisions for the Earth: Balance voice and power 328 pp. World Resources Institute Washington DC

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