The 21st century has brought many conservation challenges to the fore. One very important and significant challenge that has evoked considerable scientific interest is the fragmentation of wildlife habitat.
With rapidly expanding human populations and other competing land uses, areas that used to be continuous habitat have become broken and fragmented, isolating plant and animal populations contained within them.
Habitat fragmentation is usually a time driven process that innocuously sets in the garb of human habitation or habitat alteration and eventually accelerates with the passage of time resulting in complete isolation of originally contiguous habitat.
Populations thus isolated face survival pressures through increased competition for food and space and obligated risks in relation to disease outbreaks and episodic calamities such as fire and flood. Over a larger time span, species inhabiting isolated habitats also face the risk of extinction through mechanisms such as excessive inbreeding.
It is worthwhile to mention that studies have shown that extinction has been quite pronounced in island communities. Around 93 per cent of bird species whose extinction has been recorded since 1600 have been island species (UWI, 2006).
Habitat fragmentation and reduction at various spatial scales has been widely acknowledged as a primary cause of the decline of many species worldwide (Ehrlich 1986; Lovejoy et al., 1986; Harris, 1984; MacDonald, 2003). Habitat fragmentation generally results in smaller and more isolated animal populations (Noss, 1987, 1992; Beier 1993; Noss et al., 1996).
Smaller populations are then faced with the threat of local extinction due to stochastic events and catastrophes (Shaffer, 1978; Gilpin and Soule, 1986), and they become more susceptible to the inbreeding depression and its effects on long-term viability of populations.
Fragmentation has resulted in varied effects both on individual animals and ecological processes. Gibbs and Faarborg (1990) have reported that fragmentation and reduction in the size of habitats has resulted in decline of forest interior species such as ovenbird and Kentucky warblers showed. Kattan et al. (1994) have also reported the loss of 24 species (31 per cent of the original avifauna) in San Antonio upland forest due to effects of fragmentation.
A number of conservation biologists have recommended maintaining habitat connectivity at landscape level to reduce the isolation of fragmented habitats (Noss 1983, 1987; Noss and Harris, 1986; Craighead et al., 1997; Craighead and Vyse, 1995; Paetkau et al., 1997).
The habitat fragmentation issue is of particular relevance to developing countries where most of the biodiversity rich tropical ecosystems are located. Natural ecosystems in many developing nations are currently facing an unprecedented threat due to diverse competing pressures resulting from a burgeoning human population and unregulated economic growth. India is one of the twelve mega-biodiversity nations of the world.
Out of a total of 12, 28,153 recorded animal species, 89,451 are known to occur in India which is around 7.28 per cent of the total global faunal diversity. India is home to around 4,952 higher chordates (Table 1) of which around 175 animal species are in the International Union of Conservation of Nature and Natural Resources (IUCN) red list threat category.
India is also home to over one billion people many of whom live proximate to forest areas depending on them for their livelihood and subsistence. Furthermore, urbanization, industrialization, infrastructure development projects, agriculture, grazing, deforestation, wildlife trade and poaching continue to create tremendous stress on wildlife and pristine natural environs.
As habitats shrink and populations become more isolated on ‘habitat islands’ studded in a matrix of altered land use, serious questions on long-term survival of many key species is now being asked. The status of large cats located at the apex of the food pyramid, is a grim reminder of the intense pressure that these animals face due to habitat loss.
In recent times, considerable scientific and media attention has been focused in India on large mammals—particularly large cats—and their conflict with man primarily attributed to dwindling habitat.
The fierce conflict between man and leopard in Mumbai (Sanctuary, 2004) due to habitat loss, the small and vulnerable population of 359 Asiatic lions located in only 259 sq km of core forest habitat in Gir, Gujarat (Gujarat Forest Department, 2006); the highly endangered population of 3,600-4,000 tigers in India threatened by habitat loss and poaching (Project Tiger, 2006) are all indicative of the immense threat that these fiercely territorial apex predators face today. Shrinking habitats also mean genetic isolation for many species in the long run.
One solution to ameliorate the undesirable effects of habitat loss is to provide connectivity between isolated habitat patches through wildlife corridors. Creation of dispersal corridors has received much global attention during the last two decades. While the utility of wildlife corridors has been debated (Simberloff and Cox 1987; Simberloff et al., 1992; Beier and Noss 1998), conservationists largely believe that wildlife corridors facilitate animal dispersal from isolated habitats and help counter biological processes that lead to species extinction.
In the recent years, there has been considerable advocacy for planning dispersal corridors for wildlife in the Indian subcontinent. Even government agencies have augmented research efforts in identifying corridor opportunities for tiger conservation between important tiger reserves in India.
The declining status of wildlife has been largely attributed to extensive loss of habitat and the ensuing circumscription of wildlife to small and isolated protected areas in India eliciting conservationists to agree that connectivity between larger habitats may be the key to long-term survival of wildlife populations.