1.1 Tropical Forests and Fragmentation
Landscape level alteration caused by deforestation is an issue of major concern globally. Deforestation has serious consequences on tropical forest ecosystem. Although tropical forests cover less than 7 % of the terrestrial surface, it supports more than 50 % of known plant and animal species. Today, it is the most species rich terrestrial ecosystem and is also facing deforestation faster than any other biome in the world (Myers 1988, Myers 1990). Uncontrolled use of tropical forests for agricultural expansion, mining, development projects, forestry operations, industrialization, urbanization and exotic plantations is a major cause of forest degradation in many regions. In last two decades, an annual loss of 1 % tropical forest cover has been reported globally (Mayaux et al. 2005, FAO 2007)
Fragmentation of tropical forests is a complex phenomenon as it leads to major physical and biological changes in the forest ecosystem. Apart from causing destruction of habitat, it isolates formerly contiguous habitat, increases edge effects (McGarigal and Cushman 2002; Broadbent et.al 2008).and alters species population dynamics (Watson 2005, Broadbent et al. 2008). Opening up of canopy in dense forests disrupts the continuity of forests, changes the micro-climate and can lead to invasion of exotics. This would have direct implications on the carrying capacity of forest patches and types of species it can support. Also, because of fragmentation, populations are isolated leading to risks of in-breeding and spread of disease. The size and extent of isolation of forest fragment often determines species re-colonization potential, mortality and dispersal (Joshi et al 2005, Boyle 2007, Broadbent et al. 2008).The net effect of this is increased vulnerability of species to extinction (Myers et al. 2000) causing serious threat to biodiversity of tropics (Gascon et al 2000; Giriraj et al. 2009). Response of a species to forest fragmentation varies with the life history traits of individual species and the matrix of forest surrounding the fragment (Laurance 1990, Boyle 2008).
It is therefore necessary to determine the factors influencing the distribution of species inhabiting fragile ecosystems in order to plan management interventions for its long-term conservation.
The Western Ghats of India represents some of the best non-equatorial, tropical evergreen forests in the world. Located along the west coast of India, the Western Ghats are extremely rich in biodiversity and has the distinction of being declared as one of the 34 global biodiversity hotspots (Myers et al 2000). The Western Ghats barely covers 6 % of the country’s land but is home to more than 30 per cent of the country’s fauna. Like any other biodiversity hotspots, the Western Ghats supports many endemic species and are also facing threats of rapid deforestation (Myers 1988, 2003, Western Ghats Ecosystem Profile 2007).
The Western Ghats are divisible in two district regions based on the geology, topography, rainfall pattern and vegetation composition. The hills north of Krishna basin running along in to the states of Gujarat and Maharashtra are volcanic in origin with isolated, conical, flat-topped hills, with terraced terrain and steep slopes having a gradient of low rainfall from north to south. South of Krishna basin is the hills of Southern Western Ghats of Goa, Karnataka, Tamil Nadu and Kerala which are of Precambrian origin with high altitude plateaus and high rainfall.
Historically, the Western Ghats were well-forested and its inaccessibility prevented the people from cultivating and constructing in the region. However with the advent of British Rule followed by the spell of industrialization in post-independence era, the once inhospitable region witnessed large scale clearing of forests for giving way to development projects, commercial plantations and expanded agricultural activities. Substantial areas of lowland evergreen and semi-evergreen evergreen forests on the coastal plains to the west of the Ghats were deforested because of this (Daniels et al 1990, Stattersfield et al 1998, Western Ghats Ecosystem Profile 2007).
With a high density of 250 people/ km2, approximately 20 % of the original forest covers remains in pristine state, with very few regions having intact forest blocks. Contiguous blocks of forests larger than 200 km² are remaining in the Agasthyamala Hills, Cardamom Hills, Silent Valley-New Amarambalam Forests, and southern parts of Karnataka State (Western Ghats Ecosystem Profile 2007).
The forest loss is relatively more in Northern Western Ghats than in southern Western Ghats (Panigrahy et al. 2010, Northern Western Ghats State Report 2010). The region has witnessed rapid urban expansion and an increase in development projects since last three decades. Large scale projects for luxury townships, resorts and development project for railways, highways, power plants and mines have swept away the forest cover in the region (Mehta and Kulkarni 2010, Northern Western Ghats State Report 2010). Panigrahy et al. (2010) examined the changes in forest cover of Maharashtra Western Ghats from 1985 to 2005 based on satellite imageries. The study reported an annual decline of 0.72 % in dense forest cover and 0.42 % in the open forest cover owing to development projects, urbanization and an increase in water-bodies in the area in last two decades.
The Western Ghats of Maharashtra are in the forefront of the entire Western Ghats and therefore play a vital role in the zoogeography of India. Unlike its southern counterpart, the Maharashtra Western Ghats has not attracted much attention from the researcher community perhaps owing to its drier and fragmented landscape. The Indian or Malabar giant squirrel Ratufa indica is endemic to Western Ghats and is totally dependent on the canopy connectedness for its survival. Given the rapid rate of forest loss in this region, it was important to understand the status of giant squirrel in Maharashtra, where it is also declared as a State Animal. The Wildlife Research and Conservation Society (WRCS) of Pune in Maharashtra initiated a status survey of Malabar giant squirrel along the length of Maharashtra Western Ghats. The survey was supported by Worldwide Fund for Nature (WWF), New Delhi and Rufford Small Grants Program, United Kingdom.