Multi-scale analysis of Loktak wetlandscape using Earth Observation datasets

A wetlandscape is a landscape characterized by the presence of numerous interconnected wetlands (Bertassello et al. 2018). Loktak located in the Manipur River basin in India is a unique wetlandscape that includes numerous floodplain wetlands and associated channels. It hosts the Loktak wetland, the largest freshwater body in the northeastern India, also designated as Ramsar site and the Keibul Lamjao National Park, the only floating national park in the world. Like any other wetlands in the world, Loktak wetlandscape is also under great threat due to the changes in the hydrometeorological conditions associated with climate change as well as the human interventions in the wetlandscape and its catchment. Loktak hydro-electric project, the major anthropogenic intervention in the wetlandscape has a huge impact on the hydrology and ecology of Loktak wetland complex and to Pumlen wetland complex to a less significant level (Trisal and Manihar 2002). This work investigates the multi- and cross-scale degradation of wetlands in the Loktak wetlandscape in a nested-framework by studying hydrogeomorphic dynamics at catchment scale, wetlandscape scale, and wetland complex scale. The catchment scale encompasses surrounding uplands and hillslopes. At the wetlandscape scale, which includes interconnected wetlands and associated channels, individual wetland boundaries are demarcated using historical Corona image and recent Sentinel-2 image. By comparing historic and recent boundaries, we found that six natural wetlands of area less than 1.5km2 have completely converted into other land use types and three small wetlands with area less than 1km2 get merged with bigger ones due to barrage-induced prolonged inundation. The wetland complex scale is a cluster of hydrologically interconnected wetlands of same or different types. Loktak wetland complex has not shown any prominent change in its extent, whereas Ikop and Pumlen wetland complexes have shrunken remarkably over time. The degradation of wetlandscape is evident from other factors such as proliferation and thinning of phumdis (floating biomass) and destruction of vegetation in the catchment. The cross-scale investigation suggests the influence of both natural and anthropogenic controls on the degradation of Loktak wetlandscape. The findings of this study and the protocols developed here will help to better understand the stressors of Loktak wetlandscape and elsewhere and could be instrumental in developing a conservation and management plan. Multi-scale management of wetlandscape include the catchment-scale measures such as afforestation, protection of hills and reducing the frequency of shifting (jhum) cultivation in hilly areas, wetlandscape scale measures such as control of waste dumping, control of channel modification for builtup and then wetland scale measures such as removal of invasive species from open water, and control of athaphum farming (method of farming using phumdis). Considering that a huge proportion of population in the valley depend on these wetlands for their livelihood, accounting their needs and making them a part of any effort for the management of this ecosystem has to be one of the primary goal.