Change detection of mangrove forests in West and Central Africa with Landsat imagery

Mangroves are distributed along the coastal wetlands of tropical and subtropical regions throughout the world. They provide various ecological and socioeconomic services for humans, including coastal protection, water filtration, tourist attraction and the provision of building material, and they also serve as habitats for a variety of coastal wildlife species. The dramatic decline of mangroves in West and Central Africa during the last half century due to the conversion of mangrove forests to agricultural lands and urbanization has caused environmental issues including habitat loss, reduction of biodiversity, and increased coastal erosion. This study aims to investigate the changes of mangrove forests in the West and Central Africa (mainly located in three nations: Senegal, The Gambia and Guinea-Bissau) using Landsat imageries during the periods of 1988 to 2014. The data was processed through five main steps: (1) data pre-processing including geometric and atmospheric corrections and image normalization; (2) image classification using the decision tree algorithm; (3) accuracy assessment for the classification results, (4) change detection analysis. From the classification results, 2.1% of the mangroves were lost from 1988 to 2014, while the newly planted mangroves during the same period was 1.3%. Hence, freely available Landsat imagery provides adequate monitoring and change detection for mangrove forests.