THREAT FACTORS ON THE BUTTERFLY DIVERSITY OF WALAYAR VALLEY, THE WESTERN GHATS, INDIA

Abstract

Biodiversity is encountered by serious threats due to disturbances caused in the ecosystem by 
anthropogenic factors. Some of the key drivers of disturbances in the terrestrial ecosystem 
include land use changes such as clearing of natural vegetation for agriculture, monoculture 
plantations, forest fragmentation, various industrial activities and forest fire. These changes 
happening in the ecosystem have impact on the insects, which constitute about 80 percent of 
the species on earth. Among the insects, the butterflies are very sensitive to even minor 
changes in the environment and are considered as „bioindicators‟. Hence they are also likely 
to be much affected by the disturbances in the ecosystem. In this context, a study was carried 
out from 2012 to 2015 to find out the threat factors on butterfly diversity of Walayar Valley, 
the major break in the Western Ghats mountain system. It was found that the major threat 
factors encountered by butterflies in the valley are: forest fire, extension of monoculture 
forest plantations, degradation of forests / formation of scrub and expansion of areas under 
mining. The forest degradation started in both Kerala and Tamil Nadu part of Walayar Valley 
from 1920s and its intensity was very high during the 50 years period, up to 1970s and the 
area under scrub was increasing. The forest degradation happened from 1970s to 2010 was 
not much, compared to the earlier period. The threat factor analysis has shown that the forest 
areas lying in Kerala part of Walayar Valley has undergone more disturbances, compared to 
Tamil Nadu part of the valley. Walayar Valley has been found to shelter six species of 
endemic butterflies and 10 butterfly species listed under Wildlife (Protection) Act, 1972 
which are of conservation concern. Most of the tropical forest areas have undergone changes 
one way or other in the recent past due to anthropogenic factors and the biodiversity available 
has to be preserved in such areas now. Hence biodiversity conservation in partially modified 
landscapes, as in the case of Walayar Valley has significance and requires utmost attention. 
Managerial interventions towards reducing the impact of the threat factors as well as 
measures for eco-restoration of the disturbed ecosystem of the valley are the need of the hour
to conserve the butterfly diversity.