Original articleForest degradation assessment in the upper catchment of the river Tons using remote sensing and GIS
Introduction
The forest degradation is of great concern to the people of Himalayan states in India. The rapid socioeconomic development, expansion of agriculture, over-grazing, increased demand for fodder, timber and the firewood, excessive resin tapping and recurrent forest fires have led to the forest degradation in the Himalayas (Negi, 1982, Somanathan, 1991, Awasthi et al., 2003), and have negatively impacted the landscapes significantly (Sharma et al., 1999). Forest degradation is a process leading to a temporary or permanent deterioration in the density or the structure of the vegetation cover or its species composition (Grainer, 1993). Forest degradation does not involve a reduction of the forest area, but rather a quality decrease in its condition (Lanly, 2003). Lambin (1999) suggested that degradation of the forest cover is often a complex process, with some degree of ecological reversibility. It can result in the increased erosion, run-off and the floods, influencing downstream irrigation, fishery and the hydroelectric projects (Hodgson and Dixon, 1988). Degradation is measured in terms of crown cover or canopy density (Prabhakar et al., 2006).
Up-to-date information on the natural resources including forests is essential for sustainable development of the mountain regions. Satellite remote sensing provides near real-time data with synoptic and repetitive coverage and thus, gives significant leverage over traditional methods (Lillesand and Kiefer, 2000). Remote sensing, coupled with GIS and global positioning system (GPS), provides the capabilities to assess the forest degradation time- and cost-effectively, more so in inaccessible areas. It can play an important role in the generation of the forest cover-related information (Kushwaha, 1990, Rathore et al., 1997). Reliable information on forest degradation can help in effective management, biomass/carbon assessment and conservation (Souza et al., 2003). It can also be used for fire risk assessment, since degraded forests are highly prone to fire (Holdsworth and Uhl, 1997). This study is a part of Yamuna River Catchment Development Programme of the Ministry of Environment and Forests, Government of India. The programme is aimed to improve, over long run, the water quality in the river Yamuna through catchment treatment.
Section snippets
Study site
The upper catchment of river Tons (area 1171.7 km2), is situated within 31°00′–31°16′N and 78°00′–78°38′E in Purola sub-division of the Uttarkashi district in the Uttarakhand state (Fig. 1). It includes Govind Wildlife Sanctuary and the National Park by same name with Rupin, Supin and Sankari forest ranges. The Ministry of Environment and Forests, Government of India has identified this area for snow leopard (Uncia uncia Schreber) conservation. The terrain is mountainous with altitude varying
Results and discussion
The thematic accuracy worked out to be 89.5% (Table 1). Fig. 3 illustrates various forest degradation classes. The undegraded forest covers a total area of 303.2 km2 (25.9%). The areas south of Tons and east of Rupin and Supin rivers (tributaries of Tons) have majority of the undegraded forest. The moderately degraded forest occupies 2.6% while degraded forest occupies 4.5% of the total area. The 2.3% area is covered by severely degraded forest, requiring immediate soil conservation measures.
Conclusions
The environmental problems in the upper catchment of river Tons are very similar to those in other areas in the Himalayan region as far as they are related to geology, topography, climate, forests and the soil. The local people are entirely dependent upon the limited natural resources for fodder, medicinal plants and the timber and much of the environmental degradation in the region can be attributed to that. During winter, when the meadows get snow-covered and lower altitude grasses dry up,
Acknowledgements
The authors are thankful to the Ministry of Environment and Forests, Government of India for the financial support vide sanction number J-15011/16/2004-NRCD-II. Thanks are due to the Chief Wildlife Warden, Uttarakhand Forest Department for support during reconnaissance survey and the field verification of the thematic map.
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