Increase in Agricultural Patch Contiguity over the past three Decades in Ganga River Basin, India

Ganga River Basin (GRB) is the second most populous river basin in the world, which has been undergoing rapid land-use change during the last few decades. Here, we analyse the landscape dynamics in Indian GRB (IGRB) using three indices, i.e. class area, mean patch size and number of patches for 14 land-use and land-cover (LULC) classes using multi-temporal Landsat satellite datasets of 1975 and 2010. Major change was observed with the expansion of agricultural lands and human settlements and depletion of forests. Agricultural lands covered the highest area (>75%), where low to medium-sized patches have increased and patches with larger size have been slightly reduced in size over past decades. The highest increase in percentage of built-up land has been appropriately captured on medium-resolution satellite imageries using visual interpretation technique. Degradation and loss of forest areas were reported in terms of landscape indices; however, the increase of plantation is a positive sign in the basin. In general, we observed aggregation of agricultural patches and reduction of forest patches in small to medium patch sizes. We argue the utility of 'onscreen visual interpretation' technique in favour of LULC mapping to achieve absolute accuracy in such a heterogeneous landscape, as it incorporates interpreter's knowledge. We appreciate the free availability of Landsat imageries having very good radiometry that has opened the doors for exercises with minimum cost. Located in one of the most fertile regions of India, the basin accommodates more than 400 million human population. This has led to expansion of agriculture and built-up land at the cost of forest and other land covers. Understanding landscape dynamics could help in designing an effective land-use policy for IGRB.