Does mangrove plantation reduce coastal erosion? Assessment from the west coast of India

Mangroves are believed to stabilize the coastlines by controlling erosion and facilitating sediment deposition. Coastal managers often plant mangroves to counter coastal erosion. The state of Gujarat in West India has planted thousands of hectares of mangroves over the years, and control of coastal erosion has been one of the prime reasons of plantation. This study performed a statistical assessment of the effect of the planted mangroves on the coastline changes in the state from 1990 to 2013. The study utilized geographic information system and remote sensing data to demarcate the areas under erosion and accretion during this period, and then compared these changes with the change in mangrove cover using statistical models. This cross-sectional analysis was conducted at the level of a tehsil, an administrative unit below a district. The results show that mangrove plantation did not decrease erosion, not even after normalizing the coastline changes by the length of the coastline and using controls for physical and anthropogenic features of the tehsils. Tehsils with increased mangrove cover witnessed both increased erosion and accretion, although the latter was much higher. The geophysical features of the area appeared to be the main determinants of coastline changes in Gujarat.