Remote Sensing of Coral Reefs at NASA: Overview of Integrated Collaborations, Projects, and Products
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Science Applications and Data Distribution with International Partners

Click here to see the larger version of this imageOnce of the major purpose of NASA's support of collaboration in coral reef mapping is to find ways to get remote sensing data and derived maps into the hands of the managers that are making decisions about coral reef ecosystems. NASA has supported collaboration with three different international non-governmental organizations to help facilitate their use of remote sensing data and to improve global accessibility to maps and data. Particular areas of emphasis are in transferring technological capabilities to use remote sensing data to map coral reefs and linked land areas, and in fostering linkages for data distribution through the partners.

UNEP World Conservation Monitoring Centre

World Atlas of Coral ReefsThe UNEP-WCMC ( serves as a major provider of information for developing conservation policies around the world. They serve as the primary reef map producers for the International Coral Reef Action Network (ICRAN) ( They produced and maintain the current existing global coral reef map from a compilation of cartographic sources, and published the World Atlas of Coral Reefs ( (Spalding et al. 2001). Although the atlas is a landmark product and provides the best current estimate of the global area of emergent reef crest, it is limited by the variety of cartographic sources that were used. Only 30% of the reefs in the atlas had source data at a 1:250,000 scale or better. Sources also differed in their definitions of the reef areas that were mapped. Spatial and positional accuracy in a cartographic compilation product is also a difficult challenge.

Through partnerships with NASA, the global SeaWiFS bathymetry map was used to identify and correct errors in the WCMC reef map. For example, in this map of Kiritimati, Kiribati, the light blue pixels represent shallow depths and the black areas represent land. The existing WCMC map (red lines) has positional inaccuracies with the reef mapped on top of the land. The shallow bathymetry allows correction of the position of the reef (yellow line on the south side of the island).

Combining the SeaWiFS bathymetry product with the WCMC map has increased map accuracy for use in evaluating the global distribution of marine protected areas (Green et al. in review). The SeaWiFS bathymetry allowed identification of the level of protection of tropical shallow marine habitats around the world. Important considerations in evaluating whether shallow marine and coral reef environments are protected are the degree to which designated marine protected areas overlap (as shown in this map of Grand Cul-de-Sac Marin Reserve, Guadeloupe), and whether protected habitats are representative of the marine biodiversity of different regions.

WCMC personnel were trained by and have participated in the Millennium Coral Reef Mapping project at the University of South Florida. After the Millennium Maps are complete, a reduced "reef-no reef" global map product with uniform global accuracy will be derived as a substantial update to the World Atlas of Coral Reefs.

An important area in global coral reef conservation is evaluating changes in related marine ecosystems such as mangroves and seagrasses. WCMC is also collaborating with Johnson Space Center and Florida International University in evaluating methods for updating the World Mangrove Atlas (Spalding et al. 1997) using Landsat 7 and MODIS data.

World Resources Institute

Reefs at Risk ( is a series of projects at the World Resources Institute that develop indicators to evaluate the human pressures on coral reefs. The projects, which entail extensive collaboration with partners across each region, evaluate threats to coral reefs from coastal development, marine pollution, pollution and sedimentation from inland sources, and overexploitation of resources. A global analysis was released in 1998 (Bryant et al. 1998) and was important for raising global awareness of the extent of threats to reefs around the world. A more detailed analysis of Reefs at Risk in Southeast Asia was released in 2002 (Burke et al. 2002). A more detailed regional analysis for the Caribbean is currently in progress and expected to be released in 2004.

The main objectives for collaboration between NASA and WRI was to help improve the accuracy of input data used in the threat models in the Caribbean regional study. The Reefs at Risk methodology relies on GIS-based modeling with existing map datasets. In previous studies, the threat of pollution and sedimentation were evaluated using the 1-km IGBP DISCover/USGS Global Land Cover dataset (Belward et al. 1999) and WCMC coral reef maps as base information. These coarse datasets were not suitable for modeling the risks to many small islands in the Caribbean such as the Lesser Antilles. Such analyses need to be made at a finer spatial resolution.

Since Millennium Coral Reef Maps for the Caribbean are being completed simultaneously to the Reefs at Risk Caribbean analysis, Millennium Maps are being delivered directly to WRI to allow updated coral reef data to be used in the Reefs at Risk Caribbean analyses.

Through NASA support, Florida International University has been collaborating with WRI in evaluating different sources of higher resolution land cover data by comparing three global land cover maps (IGBP DISCover/USGS Global Land Cover (, Boston University's MODIS/Terra Land Cover (, and EarthSat's Geocover-LC ( with a custom classification using Landsat 7 data. WRI partners have been providing expert local review of the maps, and the effect of the different source data on the land pollution and sedimentation risk models is currently being determined. This will allow WRI to better understand their data needs as they complete subsequent regional Reefs at Risk Analyses.


Click here to see the larger version of this image Reefbase ( is the premier online information system on coral reefs. It includes a database of information on the location, status, legislation and management of coral reefs around the world, archives of coral bleaching observations, and data collected by the Global Coral Reef Monitoring Network ( It serves as the primary data archive and distribution center for the International Coral Reef Action Network (ICRAN) (

As part of their collaboration with NASA, ReefBase developed a new online interactive map server that allows users to interactively assemble and view key reef mapping datasets, including the coral reef and mangrove maps from UNEP-WCMC, Reefs at Risk data, ReefCheck maps, NOAA AVHRR Coral Reef Hotspot data, NASA remote sensing imagery of reefs, and the SeaWiFS shallow bathymetry product.

The Millennium Coral Reef Map products were developed so that they could be easily incorporated into ReefBase when they are complete. Test datasets have already been successfully included in the interactive map server. Plans are also being implemented to allow users to include viewing a reduced-resolution Landsat-7 layer as an option, and to link to the Landsat Coral Reef Data Archive so that users can seamlessly find the underlying data needed for management applications.