|
The impact of forest fragmentation is severe in the tropics, where biodiversity is rich, and human populations are rapidly growing. Studies show decline of forest birds [19], large wide ranging species [20] and more specifically specialised species [21] that require unique habitat for survival. It also influences distribution and availability of spatial resources, forest connectivity and edge characteristics, which are important for species persistence [22-24]. Also, trees in the fragmented habitats have higher annual tree mortality rates due to vagaries of wind [25]. Fragmentation effects cascade through the community, modifying inter-specific interactions, providing predator or competitive release, altering social relationships and movement of individuals, exacerbating edge effects, modifying nutrient flows, and potentially even affecting the composition of local population [26]. In many tropical regions, rain forest is restricted to small (less than 100 ha), isolated fragments. The conservation of such smaller fragments had not merited much attention till recent years. In regions like Western Ghats, there is not much hope for creation of more and more large-sized protected area systems due to social, economic and political constraints [27, 28]. Also, the presence of roads, power lines and substantial nearby human population has prevented the recovery [29]. ‘Forest patches’ include a diversity of habitats which are in close proximity forming a mosaic, or even in isolation like a sacred forest in the middle of a village or small town. Investigations into the ecological history of the Western Ghats reveal that the forests here, especially of altitudes below 1000 m, constitute a mosaic of patches of varied nature and ages.
In the Uttara Kannada district of central Western Ghats, where we conducted our present study, this landscape mosaic, according to traditional pre and early colonial land use, typically consisted of sacred forests (kans or devarabana), ordinary forests (kadu or adavi), shifting cultivation areas (kumri or hakkalu), leaf manure forests (betta), grazing lands (bena), etc., in addition to lands under permanent agriculture and horticulture. Such traditional mosaic within it might contain streams, ponds, waterfalls and rivers, gorges and steeps and rocky pinnacles, each with its own characteristic species composition [12, 27-28, 30]. Sacred forest fragments are shelters of biodiversity, meeting the needs of non-timber forest produce requirement and are best protected by local communities [31]. The lower altitudes of pre-historical Western Ghats, before the beginning of shifting cultivation, around 3,000 years ago, would have been covered with pristine ecosystems, more or less untrammeled by man, except by hunter-gatherers, who seldom if at all, indulged in forest alterations. Especially due to the heavy rainfall, western facing portions of the mountains would have been covered with tropical evergreen forests, laced with water courses and swamps [24,27]. Earlier studies in the Western Ghats also showed that remnants foster successional processes in natural restoration of rainforests [32]. Shifting cultivation was a major activity of forest dwelling tribals, throughout the Western Ghats, sparing only the higher altitudes. Carried out through centuries this might have altered substantially the primary evergreen forests. In sparsely populated interior places of South Indian Western Ghats, the forests would regrow and through time get back most of the original elements of the flora barring a few, as the fallow period was long (sometimes the tribes never returned to the original areas). As fire was an important factor in shifting cultivation, it may be that hygrophilous endemic tree species such as Dipterocarpus indicus and Vateria indica, failed to regenerate on slash and burn areas, but survived in protected areas like the sacred forests. The same could be true of Madhuca bourdillonii and Syzygium travancoricum (Fig. 5).
