Status and distribution of mangrove forests of the world using earth observation satellite data

Background

With many threats causing mangrove loss and degradation (e.g., sea level rise, conversion to agriculture or aquaculture, tourism, urban development, overexploitation), it is important to have accurate measurements and maps of global mangrove extent. With inconsistent monitoring across space and time, incompatible datasets, and large ranges in current global mangrove area estimates (110,000 to 240,000 km²), it is necessary to refine the global estimate of mangrove area to have a reliable baseline for monitoring global mangrove loss.

Goals and Methods

The authors used data from the Global Land Survey (GLS) to create a global map of mangrove forests at 30-m resolution for the year 2000. Landsat imagery was used to supplement gaps in GLS data. The authors mapped water bodies with supervised image classification techniques and interpreted Landsat imagery using a hybrid system of supervised and unsupervised image classification. The authors assessed the validity of the map by comparing the data with other existing global, regional, and local datasets, in addition to qualitative validation from local experts and high-resolution satellite data. 

Conclusions and Takeaways

This study estimates that mangrove forests covered 137,760 km2 globally in 2000, accounting for only 0.7% of global tropical forest area. This estimate is 12% smaller than the 2007 Food and Agriculture Organization of the United Nations (FAO) estimate, providing a more accurate estimate of global mangrove area from this study’s high-resolution and high-coverage data. This new baseline for global mangrove distribution is important for practitioners working on mangrove conservation, degradation, and above-ground carbon stocks.