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ResultsMetadata11 th International Symposium for GIS and Computer Cartography for Coastal Zones ManagementDetailed metadata was missing from many of the biodiversity data layers, including source of information, date,and method of collection or a description of the data. For example, the layer “Critical habitat sites of green, leatherbackand hawksbill turtles in the Coral Triangle”, used in a number of regional reports and in connectivity analysisof biodiversity, created by the Ministry of Forestry & WWF Indonesia, was lacking information on data collection,dates and methodology.Multiple layersFour sources of data for coral reefs were compared: United Nation Environment Program and World ConservationMonitoring Center (UNEP–WCMC) Global Distribution of Coral Reefs (2010); World Resource Institute(WRI) from the 2008 Reefs@Risk Revisited report; Global Coral Reef Monitoring Network (GCRMN); Status ofcoral reefs of the world by Wilkinson (2008) and UNEP-WCMC World Atlas of Coral Reefs by Spalding et al.(2001).The analysis of the total area of coral reefs within each country of the Coral Triangle revealed a discrepancy betweenthe two most recent data sources (Table 1). The area from WRI was approximately twice the area fromUNEP-WCMC.Table 1. Comparison of the area of coral reef (in km 2 ) calculated by several sources for the six countries of the Coral Triangle.UNEP - WCMC (2010)Global Distribution ofCoral ReefsWRI (2011) Reefs@RiskRevisitedWilkinson, C. (2008) Statusof coral reefs of the world.GCRMN.Spalding M.D. et al. (2001)World Atlas of Coral Reefs.UNEP-WCMC.Indonesia Malaysia PNG PhilippinesSolomonIslandsTimor-Leste19,805 1,687 7,126 11,852 2,802 3539,538 2,935 14,535 22,484 6,743 14650,875 4,006 NA 25,819 5,750 NA51,020 3,600 13,840 25,060 5,750 NAA closer look into the two datasets helps to understand the difference in area of coral reef cover. Both data setshave similar sources: the UNEP-WCMC data consists of vector spatial data, 85% of which was obtained from theMillennium Coral Reef Mapping Project (mapped at 30 m resolution using Landsat images), and from various othersources. The WRI data also relies mainly on the Millennium Coral Reef Mapping Project and completes it withother various sources as well. However, to standardize the data for the Reefs at Risk Revisited project, WRI convertedall their data to a 500 m grid in raster format. This procedure almost doubles the total area of coral cover, asoriginal small patches of coral reef are converted to grid cells of a 0.25 km 2 in size. The reef data was converted to500 m grids to represent the reef slopes and deeper reefs typically undetectable from satellite remote sensing.Digitization errorDigitization errors were found in both mangrove and coral reef datasets.Four sources of data for mangroves were compared: Spalding et al. (2010) World Atlas of Mangroves; Giri et al.(2011) Status and Distribution of Mangrove Forests of the World using Earth Observation Satellite data; UNEP-WCMC (1997) The Global Distribution of Mangroves and FAO (2007) The World's Mangroves 1980–2005.The analysis of the total area of mangroves within each country of the Coral Triangle revealed a discrepancyamong all the data and some specific differences between the two most recent references.A closer look at the GIS layers of the World Atlas of Mangroves showed that most of Malaysia’s mangrove hadtwo copies of extremely similar polygons which were overlaid and most likely caused the error in calculation. The36

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