A review of carbon sequestration dynamics in the Himalayan region as a function of land-use change and forest/soil degradation with special reference to Nepal

Land-use changes and degradation of forests and soils in the Hindu Kush Himalayan region have important implications for CO2 emissions and global climatic change that calls for an interdisciplinary research to analyse the complexity of the problem. This paper represents an effort in this direction by reviewing the literature on land-use changes, forest/soil degradation and their effects on C sequestration in this region. The main objective of this study was to document knowledge on C sequestration as affected by land-use changes and forest/soil degradation. We found a very few attempts at studying the subject in its entirety, and a lack of reliable data on essential ecological parameters related to the dynamics of C sequestration in the region. Estimates of land-use changes, loss of soil due to erosion and soil organic carbon contents by dominant land-use categories have been documented from the available studies in the region. Some evidence exists to show that the land-use changes and forest/soil degradation affect C pools significantly. The net emissions of C due to land-use changes in Nepal were reported to be 6.9 × 106 to 42.1 × 106 Mg year−1 by earlier studies. In contrast to these findings, our own estimate for the year 1994 was 1.47 × 106 Mg year−1, representing C emissions from fuelwood consumption and loss of soil due to erosion less C fixation due to annual vegetation growth. Finally, an analytical framework is presented for investigating the dynamics of C sequestration. On the basis of review of past studies, there appeared to be a high potential for enhancing the C sequestration in the vegetation and soils of the Himalayan region through improved management of degraded lands. It is suggested that the complexity of dynamics of C sequestration caused by diverse bio-physical and socio-economic factors in the region needs ideally be analysed by following systems approach in the future research endeavours.