title: Distribution and dynamics of mangrove forests of South Asia.
abstract: Mangrove forests in South Asia occur along the tidal sea edge of Bangladesh, India, Pakistan, and Sri Lanka. These forests provide important ecosystem goods and services to the region's dense coastal populations and support important functions of the biosphere. Mangroves are under threat from both natural and anthropogenic stressors; however the current status and dynamics of the region's mangroves are poorly understood. We mapped the current extent of mangrove forests in South Asia and identified mangrove forest cover change (gain and loss) from 2000 to 2012 using Landsat satellite data. We also conducted three case studies in Indus Delta (Pakistan), Goa (India), and Sundarbans (Bangladesh and India) to identify rates, patterns, and causes of change in greater spatial and thematic details compared to regional assessment of mangrove forests. Our findings revealed that the areal extent of mangrove forests in South Asia is approximately 1,187,476 ha representing ∼7% of the global total. Our results showed that from 2000 to 2012, 92,135 ha of mangroves were deforested and 80,461 ha were reforested with a net loss of 11,673 ha. In all three case studies, mangrove areas have remained the same or increased slightly, however, the turnover was greater than the net change. Both, natural and anthropogenic factors are responsible for the change and turnover. The major causes of forest cover change are similar throughout the region; however, specific factors may be dominant in specific areas. Major causes of deforestation in South Asia include (i) conversion to other land use (e.g. conversion to agriculture, shrimp farms, development, and human settlement), (ii) over-harvesting (e.g. grazing, browsing and lopping, and fishing), (iii) pollution, (iv) decline in freshwater availability, (v) floodings, (vi) reduction of silt deposition, (vii) coastal erosion, and (viii) disturbances from tropical cyclones and tsunamis. Our analysis in the region's diverse socio-economic and environmental conditions highlights complex patterns of mangrove distribution and change. Results from this study provide important insight to the conservation and management of the important and threatened South Asian mangrove ecosystem.
authors.affiliation: U.S. Geological Survey Earth Resources Observation and Science (EROS) Center, Sioux Falls, SD 57198, USA. Electronic address: cgiri@usgs.gov.
authors.forename: Chandra
authors.initials: C
authors.lastname: Giri
authors.affiliation: ASRC InuTeq, Contractor to U.S. Geological Survey Earth Resources Observation and Science (EROS) Center, Sioux Falls, SD 57198, USA.
authors.forename: Jordan
authors.initials: J
authors.lastname: Long
authors.affiliation: World Wide Fund for Nature (WWF), Pakistan; The Hong Kong Polytechnic University, Hong Kong.
authors.forename: Sawaid
authors.initials: S
authors.lastname: Abbas
authors.affiliation: Council of Scientific & Industrial Research (CSIR)-National Institute of Oceanography, Dona Paula, Goa 403004, India.
authors.forename: R Mani
authors.initials: RM
authors.lastname: Murali
authors.affiliation: International Center for Integrated Mountain Development (ICIMOD), Kathmandu, Nepal.
authors.forename: Faisal M
authors.initials: FM
authors.lastname: Qamer
authors.affiliation: SGT, Contractor to U.S. Geological Survey Earth Resources Observation and Science (EROS) Center, Sioux Falls, SD 57198, USA.
authors.forename: Bruce
authors.initials: B
authors.lastname: Pengra
authors.affiliation: Google Earth Engine, CA, USA.
authors.forename: David
authors.initials: D
authors.lastname: Thau
mesh_terms: D001210:Asia, Southeastern; D003247:Conservation of Natural Resources / Q000379:methods; D017753:Ecosystem; D004784:Environmental Monitoring / Q000379:methods*; D065928:Forests; D006801:Humans; D058998:Remote Sensing Technology; D053833:Wetlands
keywords: Image processing; Landsat; Mangrove forest cover change; Mangrove forests; Remote sensing; South Asia