Palandro D. A. auteur aut IRD Andréfouët Serge auteur aut IRD Hu C. auteur aut IRD Hallock P. auteur aut IRD Muller-Karger F. E. auteur aut IRD Dustan P. auteur aut IRD Callahan M. K. auteur aut IRD Kranenburg C. auteur aut IRD Beaver C. R. auteur aut IRD text journalArticle eng text/pdf born digital access The loss of coral reef habitats has been witnessed at a global scale including in the Florida Keys and the Caribbean. In addition to field surveys that can be spatially limited, remote sensing can provide a synoptic view of the changes occurring on coral reef habitats. Here, we utilize an 18-year time series of Landsat 5/TM and 7/ETM+ images to assess changes in eight coral reef sites in the Florida Keys National Marine Sanctuary, namely Carysfort Reef, Grecian Rocks, Molasses Reef, Conch Reef, Sombrero Reef, Looe Key Reef, Western Sambo and Sand Key Reef. Twenty-eight Landsat images (1984-2002) were used, with imagery gathered every 2 years during spring, and every 6 years during fall. The image dataset was georectified, calibrated to remote sensing reflectance and corrected for atmospheric and water-column effects. A Mahalanobis distance classification was trained for four habitat classes ('coral', 'sand', 'bare hardbottom' and 'covered hardbottom') using in situ ground-truthing data collected in 2003-2004 and using the spectral statistics from a 2002 image. The red band was considered useful only for benthic habitats in depths less than 6 m. Overall mean coral habitat loss for all sites classified by Landsat was 61% (3.4%/year), from a percentage habitat cover of 19% (1984) down to 7.6% (2002). The classification results for the eight different sites were critically reviewed. A detailed pixel by pixel examination of the spatial patterns across time suggests that the results range from ecologically plausible to unreliable due to spatial inconsistencies and/or improbable ecological successions. In situ monitoring data acquired by the Coral Reef Evaluation and Monitoring Project (CREMP) for the eight reef sites between 1996 and 2002 showed a loss in coral cover of 52% (8.7%/year), whereas the Landsat-derived coral habitat areas decreased by 37% (6.2%/year). A direct trend comparison between the entire CREMP percent coral cover data set (1996-2004) and the entire Landsat-derived coral habitat areas showed no significant difference between the two time series (ANCOVA; F-test, p = 0.303, n = 32), despite the different scales of measurements. specialized Change detection Classification Coral reef habitat Landsat Habitat fragmentation Phase shift Strategy shift Cremp Caribbean 126 036 112 8 3388-3399 2008 0034-4257 https://www.documentation.ird.fr/hor/fdi:010042708 10.1016/j.rse.2008.02.015 0034-4257 [F B010042708] https://www.documentation.ird.fr/hor/fdi:010042708 https://www.documentation.ird.fr/intranet/publi/2008/08/010042708.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2008-09-19 2017-08-23 fdi:010042708 fre