The Physical Environment
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Biogeography of the Earth

Digging Deeper: Habitat Degradation and Human Activity

Habitat encroachment, fragmentation, and destruction has produced a plethora of problems. Habitat destruction is a leading cause of species endangerment. Habitat encroachment increases the contact between human populations and animal populations. Shrinking habitat and accessible sources of food from expanding urban and suburban land use have brought animals and humans into conflict. The loss of tiger prey and presence of livestock have increased attacks on villagers living near tiger habitat in India. Alligators in homeowners backyards is becoming a more frequent site in Florida as urban sprawl invades the state's wetlands. Deer are a nuisance in many suburban areas, destroying gardens and posing a threat to motorists.

Habitat encroachment is responsible for the recent emergence of diseases like Ebola as a threat to humans. Intact habitats tend to inhibit the spread of infectious agents. Damaged, altered, and degraded habitats trigger the spread of new and existing diseases to humans. A 2005 United Nations Global Environment Outlook Year Book 2004/5 reported that the deadly Nipah virus, normally found in Asian fruit bats, is believed to have passed over to humans. Land clearance for palm plantations brought bats in contact with swine, and then humans as their habitat shrunk. The geographic range and seasonality of mosquito-borne diseases like malaria and dengue fever, are very sensitive to changes in climate.

Illegal logging is the greatest threat to the survival of the orangutan. Native to the Indian Ocean islands of Sumatra, it is estimated that no more that 60,000 wild orangutans are left worldwide, half the population that existed a mere 10 years ago.
Forest fires, poaching and conversion of jungles to palm plantations have also decimated their populations. Living in trees, the great apes feed on insects and fruits, and in turn, disperse seeds that regenerate the tropical forests. In spite of government declarations to curb illegal logging, environmental activists blame  political corruption, and of will and insufficient resources to halt the multibillion dollar illegal logging activity.

Human conflict has deviated habitats and threatened biodiversity in many regions, especially Africa. But remarkably, some have managed to survive. Listen to NPR's report "After Sudan's Civil War, Where The Wild Things Are" and learn the region is hoping to capitalize on eco-tourism.

Wildlife Corridors

Wildlife require large areas to seek out food, mates, and nesting sites. Habitat fragmentation restricts wildlife movement resulting in overcrowding, over exploitation of resources and species endangerment. Scientists are attempting to preserve wildlife by creating corridors between fragmented portions of habitat. Wildlife corridors allow young animals to seek new territory and maintain gene flow between individual habitats thus improving species fitness. Only recently have scientists been able to show that wildlife corridors work.wildlife corridor

Figure DD.1 Wildlife corridors connect critical habitats in the agricultural heartland of Iowa. (Courtesy NRCS)

Wildlife corridors like those seen here in Iowa permit animals to exploit a variety of resources without having to cross unfriendly terrain like roads, lawns, or barren farm fields.

The Terai Arc is a fifty year effort to reconnect 11 national parks in India and Nepal with one continuous corridor of protected areas. Preliminary data from the Khata corridor between Nepal's Royal Bardia National Park and the Katarniaghat Wildlife Sanctuary of India show use by tigers and elephants. The presence of Spotted Deer and Wild Boar hoof prints provide additional evidence of corridor use.



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For Citation: Ritter, Michael E. The Physical Environment: an Introduction to Physical Geography.
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