Is aquaculture development responsible for mangrove conversion in India? - A geospatial study to assess the influence of natural and anthropogenic factors on mangroves in the last three decades

Abstract

Aquaculture was cited as the primary factor for the reduction of mangrove area worldwide. But, there is no data available on the extent of conversion of mangroves for aquaculture in India, the second largest country in global aquaculture production. The present study assessed the factors of changes in mangroves area between the pre aquaculture period and recent years. Landsat TM images of 1988, Sentinel 2 A images of 2018, geospatial analysis, ground truth verification, post-classification approach, and accuracy assessment were used for the assessment. Comparing the extent of mangroves area in 1988 with 2018, the gain and loss was 278% and 30% in Kerala, 859% and 19% in Karnataka, 204% and 18% in Maharashtra, and 4100 and 20% in Daman and Diu respectively. Mangrove extent has increased due to restoration activities, while lost due to coastal erosion and other developmental activities. Combining mangrove statistics drawn from this study with available data from earlier study, indicate that the aquaculture has converted 2052 ha of mangroves, which represents 0.66% of India's mangrove area. The extent of mangroves increased by 20.72% in India between 1988 and 2018. There is a possibility that part of the mangrove - converted lands are privately owned. Besides, Coastal Aquaculture Authority Act of 2005 prohibits the use of mangrove lands to aquaculture. The present study proves that shrimp aquaculture is not accountable for the large-scale changes in the mangrove lands of India, except in Andhra Pradesh State. However, it demands the land use policy to protect the mangrove lands in private owned lands by allocating alternate resource space, and monitoring periodically.