We visited each of the coastal sites identified in the Google Earth images and made in each one a rapid vegetation survey to assess the status of the ecological communities and confirm or reject the hypotheses developed using the remote sensing images. The detailed methods for our vegetation survey are given as section S1. Our main goal in this ground-truthing survey was to establish whether the coastal plant communities showed the effects of accretion or recession. In accreting (growing) coasts, we expected to find a gradient with young pioneering dune plants in the seaward fringe gradually transitioning onto fixed dunes, followed by a mature coastal bar forest, and then onto the inland lagoon communities of mangroves (24). In receding (eroding) coasts, we expected to find older trees, typical of more inland communities, in the seaward fringe being exposed directly to the erosive action of the waves. The relationship between plant diversity, expressed as species richness in 1 ha of coastal sandbar, and coastal accretion/erosion rates was evaluated using log-linear regression.