The Extinction Website - Habitat Loss

Habitat loss is probably the greatest threat to the variety of life on this planet today. It is identified as a main threat to 85% of all species described in the IUCN's 2004 Red List (those species officially classified as "Threatened" and "Endangered"). Increasing food production is a major agent for the conversion of natural habitat into agricultural land.

Photo: Orbital photograph of human deforestation in progress in the Tierras Bajas project in eastern Bolivia. Photograph courtesy NASA.

Why is it happening?

Forest loss and degradation is mostly caused by the expansion of agricultural land, intensive harvesting of timber, wood for fuel and other forest products, as well as overgrazing. (WWF, 2005)

High land conversion rates

The net loss in global forest area during the 1990s was about 94 million ha (equivalent to 2.4% of total forests). It is estimated that in the 1990s, almost 70% of deforested areas were converted to agricultural land. Around half of the world's original forests have disappeared, and they are still being removed at a rate 10x higher than any possible level of regrowth. As tropical forests contain at least half the Earth's species, the clearance of some 17 million hectares each year is a dramatic loss. (WWF, 2005)

Coastal and marine areas

Human impact on terrestrial and marine natural resources results in marine and coastal degradation. Population growth, urbanization, industrialisation and tourism are all factors. In 1994, it was estimated that 37% of the global population lived within 60 km of the coast. Poverty, consumption and land-use patterns contribute to the degradation of marine habitats and to the destruction of the species that rely on them to survive. (WWF, 2005)

The number of species in an isolated fragmented habitat will decrease over time, and the number of individual of a species will frequently decrease too, due to inbreeding, overkill (people get access to those areas), etc. It depend per species how its sensitivity to fragmentation is, thus how high their risk of extinction is. At least nine ecological or life history traits have been proposed as factors determining their sensitivity, namely: rarity, dispersal ability, degree of specialisation, niche location, population variability, tropic status, adult survival rate, longevity, and the intrinsic rate of population increase (Baillie et al., 2004). Animals that have become extinct due to habitat destruction are the Palestinian Painted Frog, Arc-form Pearly Mussel, Arcuate Pearly Mussel, Xerces Blue, etc.

Palestinian Painted Frog - Discoglossus nigriventer
The Palestinian or Israel Painted Frog was known from the eastern shores of the Hula wetlands (Lake Hula) in Northern Israel, and possible in adjacent parts of Syria (Syrian Arab Republic). The species inhabited freshwater swamp areas. The wetlands where this species relied on were drained for mainly agricultural purposes in the 1950’s like making the land suitable for agriculture, but also in an attempt to eradicate malaria. Of the original 6000 ha of wetlands, only an area of 320 ha has remained Although this remaining area was set aside as a nature reserve in 1964, this could not prevent the extinction of certain endemic species, including the Palestinian Painted Frog. This species has not been reported since 1955, when Steinitz collected it. Image © Kevin J. Caley.
Arc-form Pearly Mussel - Epioblasma arcaeformis
The Arc-form Pearly Mussel or Sugarspoon lived in the United States of America. It was found in the states Alabama, Kentucky, and Tennessee. This freshwater species occurred in the Cumberland and Tennessee River systems. The Arc-form Pearly Mussel was found in medium to large rivers in shoal and riffle areas. The habitat of this species has been severely modified or destroyed by damming. Damming along the entire river systems and also pollution had a negative impact on this species. Annual surveys are conducted throughout the whole system and the species has not been collected for over 50 years and probably went extinct in 1940. (Bogan, 2000)

The Emerald network is a network of areas of special conservation interest (ASCIs), which is to be established in the territory of the contracting parties and observer States to the Bern Convention, including, among others, central and east European countries and the European Union (EU) Member States. For EU Member States, Emerald network sites are those of the Natura 2000 network. (EEA, 2005)

The Yellowstone to Yukon Conservation Initiative or Y2Y is a joint Canada- US network of over 800 organizations and individuals interested in restoring and maintaining the Yellowstone to Yukon region. The group works with local communities, through education and stewardship programs, to encourage conservation of the area. The broad goal of the project is to create a life-sustaining web of protected wildlife cores and connecting wildlife movement corridors. The group was created in 1993 when a small group of scientists and conservation minded people met near Calgary, Alberta, Canada.

Wildlife crossings reconnect habitats, allowing animals to cross roads safely. They are widely used in Europe, where efforts to protect wildlife have involved underpasses, amphibian tunnels, and tunnels for small mammals such as otters, hedgehogs, and badgers. The Humane Society reports that the more than 600 tunnels installed under both major and minor roads in the Netherlands have helped to substantially increase population levels of the endangered European badger.

Photo: Wildlife crossing the "Woeste Hoeve" in the Netherlands. Photographed by Henk Muller in 2002 and released under the GNU Free Documentation License.

A wildlife corridor is the artificial joining of fragmented habitats. This helps to increase the gene flows between the individual habitats which improves the fitness of species. Wildlife corridors are created as a means of conservation or general improvement of the environment. Wildlife corridors are susceptible to the edge effect, that is that certain species do not prosper near the edges of an ecosystem. Wildlife corridors sometimes cause controversy if they affect or inconvenience the human population.

Baillie, J.E.M., Hilton-Taylor, C. and Stuart, S.N. (eds) 2004. 2004 IUCN Red List of Threatened Species. A Global Species Assessment. IUCN, Gland, Switzerland and Cambridge, UK. [PDF available via http://www.iucn.org/themes/ssc/red_list_2004/main_EN.htm].

Bogan, A.E. 2000. Epioblasma arcaeformis. In: IUCN 2004. 2004 IUCN Red List of Threatened Species. <www.redlist.org>. Downloaded on 21 September 2005.

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