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Author: search.filters.author.Habib, BilalSubject: search.filters.subject.Flora

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    Assessment of impacts of State highway 33 on flora and fauna of Nagarhole Tiger Reserve, India
    (Wildlife Institute of India, Dehradun, 2020) Habib, Bilal
    As part of the project funded by the National Tiger Conservation Authority, New Delhi, three sites were chosen for study- the Central Indian tiger landscape including major roads cutting across the animal corridors in the landscape, the National Highway 37 (now 715) cutting through the Kaziranga-Karbi Anglong landscape in Assam, and the State Highway 33 passing through the Nagarhole Tiger Reserve, Karnataka. At Nagarhole Tiger reserve, we intended to study the difference in the impacts of the SH 33 along its two stretches – one that is completely closed to traffic (decommissioned segment) and the other stretch that is closed for night time traffic (night traffic closed segment). We compared the floral (tree species composition and richness), and faunal (ungulate group size and composition, habitat use and activity patterns) characteristics along the two road stretches. We found that tree and sapling species richness was found to be higher in the decommissioned road segment as compared to the night traffic closed road segment, both of which comprised predominantly of native vegetation. On the other hand, shrubs and herbs had higher species richness in the night traffic closed road segment. We found higher species richness and cover of grasses, shrubs and herbs in the night traffic closed road segment, which can be attributed to the edge effect. Even though both the segments of the highway under study are homogenous in respect of rainfall regime, forest type and are managed as part of national park under the same management objectives (Gubbi et al. 2012), results of shrub and sapling study indicate that there exists some distinguishing factors along the two segments so as to favor different species. A further detailed study is required to point out the factors responsible. Contrary to the general understanding, invasive species cover for two of the common invasive species (Lantana camara and Eupatorium odoratum) was higher in the area devoid of traffic as compared to the night traffic closed road segment. This can be attributed to increased light intensity on the forest floor due to lower canopy cover in the decommissioned road segment and higher animal activity, who acts as seed dispersers. Lower canopy cover in decommissioned road segment can be the result of breakage of canopy and crushing of new regeneration by higher presence and more frequent activity of large mammals, like elephants. Mean group size of chital was found to be higher in the night traffic closed road segment, whereas mean crowding was higher in the decommissioned road segment. Higher presence of chital in the night traffic closed road segment can be because of availability of more fodder species and less risk of predation. In the decommissioned road segment, chital and wild pig’s habitat use is not affected by the distance from the state highway, whereas, sambar and elephant’s habitat choice is determined by distance from the highway. There has been a 16% increase in the traffic volume from 553 vehicles /day in the last 9 years as reported by Gubbi et al. (2012), to 659 ± 139.70 as reported in our study. However, though there has been an increase in the traffic volume, it is at a slower rate as compared to the increase from 2003 to 2010 level. The average speed of vehicles ranged from 27.5 MPH to 35.4 MPH. We found that in the night traffic closed road segment, animals have modified their activity periods to avoid the vehicular traffic. Most of the mammals are either active in the early morning hours before the road is opened for vehicular movement or late evenings after the road is closed. This suggests that there is a difference in activity pattern of these mammals along both the road segments, in order to understand which a further detailed study about behavior modification of mammals in relation to traffic and other road related disturbances needs to be carried out.