Post-Tsunami Land Degradation On A South Asian Island: Implications For Conservation Priorities

In recent decades, land degradation has accelerated due to an increase in unsustainable human activities. In a case-study of the Andaman Islands, located in the South Asian region, changes in land degradation types, soil erosion, and the effect of conservation measures for pre- (2000) and post-2004 tsunami periods (2006, 2019) were recorded using temporal remote sensing data (LANDSAT, RESOURCESAT, CARTOSAT), field observations and a GIS-based revised universal soil loss equation (RUSLE). The results showed that erosion, leaching, acidification, salinization, and drainage congestion were the major land degradation processes that could be traced to post-tsunami human activities (R-2 = 0.634). The study revealed significant forest cover loss during 2006-2019 (3.76%) compared to 2000-2006 (0.61%), while it revealed increased areas under settlement (14 km(2)) and mining (22 km(2)). The annual crop area exhibited a 0.42% loss, whereas the plantation crop area increased by 0.46%, indicating the abandonment of annual crops that resulted in an increased fallow area (21 km(2)) during the post-tsunami period. As a consequence, degraded land increased by 2.5% of the total geographical area which was affaected by water erosion (2.3%) and chemical degradation (0.25%). The average erosion rate varied from 0.7 to 108 t ha(-1)yr(-1) in 2000 but increased by 47% during the post-tsunami period due to mining, settlement, and vegetable cultivation on slopes, as indicated by high cover management, support practice, and slope length factors. Practicing suitable conservation measures can provide a conservation benefit of 105,560 t yr(-1) and a reduction in other forms of degradation without compromising the food production area.