Habitat disturbance is the largest single cause of biodiversity loss. Over the past 10,000 years, billions of hectares of forests, woodlands and grasslands have been converted to commercial forests, croplands and grazing lands.
Apart from loss of absolute habitat area, a serious problem is habitat fragmentation, i.e., reduction of habitat into scattered patches (Cunningham and Cunningham, 2005). Half of the world’s original forests cover including over 45% of tropical moist forests and approximately 70% of tropical dry forests are reported to be lost.
World’s remaining forests cover is being depicted by about 1, 60,000 sq. km per year. With current rate of deforestation, 50 to 90% of earth’s forest inhabiting species is projected to be lost by the mid-21st century (vide Mandal, 2006).
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About half of world’s wetlands are known to be destroyed. California has lost 91% of its wetland during the past 200 years. Wetlands destruction due to conversion of mangrove swamps to fish ponds, driving waters away from their floodplains, draining wetlands for agriculture and damage by pollution is on record.
An assessment of wildlife habitat loss in tropical Asia in 1986 reported that India has already lost about 80% of its natural habitat. Tropical rain forests, tropical dry forests, wetlands, mangroves and grasslands are examples of threatened habitats.
Habitat fragmentation by roads, fields, canals, power lines etc., limits species potential for dispersal and colonization. Physical degradation of forests habitat due to ground fire seriously affects rich perennial wild plants along with entomofauna inhabiting forests floor.
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Basic data on biology and ecology are needed to understand habitat requirements, capacity for population recovery, dispersal ability and vulnerability of species to environmental change. Most species extinctions between 1000 AD to 2000 AD were particularly due to tropical forest destruction.
More than 40% of earth’s biomass is tied up in humans, livestock and crops. Extinction of species decreases ecosystem stability. Further reduction in ecological complexity would collapse global ecosystem.
Habitat and site based action frequently taken for conserving existing habitat, maintaining the current habitat quality and habitat management may be required to increase carrying capacity. Habitat restoration recreates conditions for species persistence. Growing demand for food by a larger global population could drive the conversion of an additional 10 billion hectares of unmodified ecosystem to agriculture by 2050.