Land Degradation in Bihar, India: An Assessment Using Rain-Use Efficiency and Residual Trend Analysis

Abstract

Land degradation, a major environmental problem, poses threats to agricultural, social and economic stability of many regions of the world. In India, ~ 37% of the total land area is estimated to be degraded. Although assessment of land degradation in arid and semiarid regions of India has advanced through remote sensing time-series analysis such as rain-use efficiency (RUE) and residual trend analysis (RESTREND), the sub-humid and other regions mostly remain unexplored in this respect. In this study, land degradation in Bihar, a sub-humid state, was quantitatively assessed through RUE and RESTREND from 1995 to 2011. RUE is the ratio of aboveground net primary productivity to precipitation and has been widely used as a measure of land degradation. RESTREND, on the other hand, examines the trend of NDVI residuals, which is the difference between observed NDVI and predicted NDVI from rainfall data. Results indicate that RESTREND effectively estimated the extent of human-induced land degradation in Bihar as 4.73 M ha. Agro-climatic zone IIIB, the driest zone, has the highest percentage of degraded lands (33%), while Zone IIIA has the lowest percent of degraded lands (17%). Zones I and II each account for 25% of the degraded lands, most of which are affected by waterlogging and salinity. Although other land degradation databases have also indicated a rapid increase in land degradation across Bihar, it needs more ground-based data collection to substantiate it. The problem, however, may further aggravate with global warming, which calls for policy interventions such as adopting agroforestry, practicing sustainable agriculture and making shifts in cropping patterns.