Report of the Western Ghats Ecology Expert Panel - Part II : Geological and Biological Landscapes
Opinion
29/10/2018
1510.
He suggests that although there is not adequate amount of published information to substantiate this observation, Pascal (1988) can be used as a basis for the following speculation : -
* The resilience of wet (rainfall of 2000 mm and above) lowland landscapes in the Western Ghats is inversely related to the length of the dry
*Landscapes that receive rainfall in excess of 3000 mm or 5000 mm are apparently vulnerable to desiccation (affecting natural regeneration of wet evergreen vegetation) when the length of the dry season exceeds a certain threshold.
*Within a rainfall regime, human impacts such as extensive opening of canopy (as experienced during shifting cultivation and clear-felling operations), fire and grazing can transform the vegetation in vulnerable landscapes more drastically (often irreversibly) than in those that enjoy shorter dry seasons.
* In the Western Ghats, lower resilience in wet landscapes that experience dry seasons in excess of 6 months has led to irreversible changes in the woody plant species composition of the lowland evergreen vegetation types.
* Transformation that is initially apparent as diversification of vegetation types (as seen in L3), becomes more rapid and drastic with longer dry seasons (as witnessed in L2) and is complete and irreversible resulting in total loss of a pristine plant community as that L1 has experienced.
* The present condition and distribution of Dipterocarpus-dominated lowland wet evergreen vegetation seem to be a good indicator of landscape level resilience in the Western Ghats.
*The rather homogeneous lowland Dipterocarpus-dominated wet evergreen vegetation, when pristine, extended north into the Uttara Kannada (L2) district if not further into southwestern Maharashtra.
* The Dipterocarpus indicus dominated wet evergreen vegetation diversified into 4 distinct sub-types and the Dipterocarpus indicus-Persea macrantha sub-type gave way to a distinct Persea macrantha-dominated type in Uttara Kannada (in which Dipterocarpus indicus may still be sporadically found) more recently.
* Persea macrantha-dominated wet evergreen forests may also have occurred in the landscape north of Goa (L1) during recent history; Pascal (1988) has listed this species as occasional in the medium elevation Memecylon umbellatum-Syzigium cumini-Actinodaphne angustifolia type of wet evergreen forests of Matheran and Mahabaleshwar (Maharashtra).
* Pascal (1988) attributes the drastic transformation in the plant species composition of the wet evergreen forests of Maharashtra to shifting cultivation and the long dry season.
Landscapes with least resilience in the Western Ghats
Daniels points to the fact that‚ landscapes that have shown the least resilience are mainly located in the Western Ghats of Karnataka, Goa and Maharashtra. Whereas the least resilient landscape L1 that is spread across Maharashtra has been totally denuded of the original wet evergreen forest type, the Western Ghats of Karnataka (L2 and L3) are in various stages of recovery. The Western Ghats that run south beginning around Shimoga-Kodachadri latitude
(L3) is clearly the transition. Better ecological management of the landscape can help it recover and merge with the southern Western Ghats. Negligent management will certainly degrade it further and push it to an ecological state comparable with that of L2 and eventually L1.?
He points to the higher beta diversity (or species turnover from locality to locality) in L3, a spatially homogeneous landscape, and suggests this may be the first indication of low resilience and higher ecological sensitivity. He concludes by stating that ‚vegetation, the primary determinant of biodiversity, is not quite influenced by the underlying geological formations in the Western Ghats.
Spatial heterogeneity, therefore, is best explained by rainfall, length of the dry season and topography.?
He concludes that, in this regard, a spatially homogeneous landscape with high levels of beta diversity should be a matter of ecological concern.?
JAIHIND
VANDMATHARAM
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