SATELLITE MAPPING OF THE DEVELOPMENT OF SHRIMP AQUACULTURE, AND ITS IMPACTS ON MANGROVES AND OTHER COASTAL WETLANDS

Given the explosive development of shrimp aquaculture in recent decades, Clark Labs has developed a semi-automated mapping program based on Landsat satellite imagery to facilitate monitoring. Working in conjunction with the Gordon and Betty Moore Foundation, and its partners such as the World Wildlife Fund, mapping began in 2014 and continues on an ongoing basis.

To date, 8 countries have been mapped for 1999, 2014 and 2018: Bangladesh, Cambodia, Ecuador, India, Indonesia, Myanmar, Thailand and Vietnam. Landsat 8 OLI imagery is processed to yield 15m resolution imagery over 7 spectral reflectance bands over the visible, near- and middle-infrared wavelengths. A team of analysts identify representative examples of the land cover classes of interest in the imagery, after which machine learning computer algorithms complete the classification. The key classes include pond aquaculture, mangroves and other coastal wetlands, from which a variety of change maps can be produced (Figure 1).

The mapped data are made  publicly available through an interactive web map which also provides the ability to download the data as georeferenced layers for Geographic Information Systems (GIS). The results indicate a rapidly growing industry. For example, just between 2014 and 2018 there has been a net gain of 1665 km2 of pond aquaculture across the 8 countries (92% of which came from Indonesia and India). While 41% of this came from mangrove, there has actually been a net gain in mangrove as a result of restoration and new colonization (2238 km2).

Figure 1. Example of the change map from 2014 to 2018 in the Mahakam Delta, East Kalimantan, Indonesia. The red areas indicate mangroves that were converted to pond aquaculture over this period. Dark green areas are remaining mangrove while light blue areas are pond aquaculture in both 2014 and 2018. Gray areas are other land covers.