The following summarizes key findings of the PAGE study on conditions and trends in coastal zone extent and change, as well as the quality and availability of data.
In 1995, over 2.2 billion people -39 percent of the world's population- lived within 100 km of a coast, an increase from 2 billion people in 1990. The coastal area accounts for only 20 percent of all land area.
Nineteen percent of all lands within 100 km of the coast (excluding Antarctica and water bodies) are classified as altered, meaning they are in agricultural or urban uses; 10 percent are semialtered, involving a mosaic of natural and altered vegetation; and 71 percent fall within the least modified category. A large percentage of this least modified category includes many uninhabited areas in northern latitudes.
Many important coastal habitats, such as mangroves, wetlands, seagrasses, and coral reefs, are disappearing at a fast pace. Anywhere from 5 to 80 percent of original mangrove area in various countries, where such data are available, is believed to have been lost. Extensive losses have occurred particularly in the last 50 years.
In the 24 countries for which sufficient data were available, trawling grounds encompass 8.8 million km², of which about 5.2 million km² are located on the continental shelves. This represents about 57 percent of the total continental shelf area of these countries.
Though highly scale dependent, this analysis presents a new standardized estimate of coastline length by country. The associated total coastline length for the world is 1.6 million kilometers. This study also presents new estimates of ocean surface area within the 200 nautical miles limits of most countries.
Information on the location and extent of coastal ecosystems is very incomplete and inconsistent at the global level.
Historical data describing previous extent of habitats, against which we might hope to measure change, are very limited. Where no historical data exist, the possibility of predictive mapping should be considered, using existing climatic, oceanographic, and topographic data combined with biogeographic information.
There is an urgent need for better and more consistent classification schemes and data sets characterizing the world's coasts. Particular effort needs to be focussed on mapping the distribution of sandy and rocky shores, salt marshes, seagrasses, tidal mudflats, and lagoons.
Coastal habitats occur over relatively small spatial units, are often submerged, and are, therefore, difficult to assess with the coarse-scale global sensors often used for other terrestrial ecosystems. High-resolution remote sensing capabilities in this area are improving rapidly, but are not yet being widely applied.
The effects of human disturbances to ecosystems, such as trawling, are poorly documented. More accurate evaluation of impacts will require higher resolution data as well as site exploration.
PAGE measures and indicators
--------------------------------------------------------------------------------
Data sources and comments
--------------------------------------------------------------------------------
Coastal zone extent Pruett, L. and J. Cimino. 2000. Coastal Length, Area of Continental Shelf, Territorial Ssea, Claimed Exclusive Economic Zone, and Exclusive Fishing Zone. Unpublished data derived from Global Maritime Boundaries Database. Fairfax VA: Veridian-MRJ Technology Solutions.
Estimates of coastline length by country calculated from a globally consistent data set (World Vector Shoreline) at a uniform scale of 1:250,000. Other estimates calculated from Global Maritime Boundaries Database (Veridian-MRJ Technology Solutions, 2000).
--------------------------------------------------------------------------------
Characterization of natural features
UNEP-WCMC (United Nations Environment Programme - World Conservation Monitoring Centre). 1999a. Global Coral Reef Distribution. GIS data from the UNEP-WCMC Biodiversity Map Library. Cambridge, UK: UNEP-WCMC.
UNEP-WCMC (United Nations Environment Programme - World Conservation Monitoring Centre). 1999b. Global Mangrove Distribution. GIS data from the UNEP-WCMC Biodiversity Map Library. Cambridge, UK: UNEP-WCMC.
UNEP-WCMC (United Nations Environment Programme - World Conservation Monitoring Centre). 1998. Global Wetland Distribution. GIS data from the UNEP-WCMC Biodiversity Map Library. Cambridge, UK: UNEP-WCMC.
NSIDC (National Snow and Ice Data Center). 1999. DMSP SSM/I Brightness Temperatures and Sea Ice Concentration Grids for the Polar Regions, 1987–1998. Boulder, CO: NSIDC Distributed Active Archive Center, University of Colorado at Boulder.
LOICZ (Land-Ocean Interactions in the Coastal Zone). 1998. Coastal Typology Dataset. Texel, The Netherlands: LOICZ International Project Office, International Geosphere-Biosphere Programme. Available on-line at: http://kellia.nioz.nl/loicz/data.htm
ESRI (Environmental Systems Research Institute, Inc). 1992. ArcWorld 1:3M. Continental Coverage. CD-ROM. Redlands, CA: ESRI.
ESRI (Environmental Systems Research Institute, Inc). 1993. Digital Chart of the World. CD-ROM. Redlands, CA: ESRI.
IOC (Intergovernmental Oceanographic Commission), IHO (International Hydrographic Organization), and BODC (British Oceanographic Data Centre). 1997. General Bathymetric Chart of the Oceans (GEBCO) 97: The 1997 Edition of the GEBCO Digital Atlas. Birkenhead, UK: British Oceanographic Data Centre.
Stutz, M.L. 1999. Distribution of Barrier Islands. Unpublished data.
Stutz, M.L., A.C. Trembanis, and O.H. Pilkey. 1999. “Barrier Island Morphology on the U.S., Canadian, and Russian Arctic Coasts.” EOS Transactions, AGU 80(46): F519.
The typology represents a hierarchical summary of coastal features relevant to the goods and services discussed in this report. Scale and quality of input data vary. This analysis does not directly address climate, currents, or substrate.
--------------------------------------------------------------------------------
Extent of natural habitats Spalding M.D., F. Blasco, C.D. Field. eds. 1997. World Mangrove Atlas. Okinawa, Japan: The International Society for Mangrove Ecosystems.
Spalding, M.D. and A.M. Grenfell. 1997. “New Estimates of Global and Regional Coral Reef Areas.“ Coral Reefs 16: 225–230.
UNEP-WCMC (United Nations Environment Programme - World Conservation Monitoring Centre). 1998. Global Wetland Distribution. GIS data from the UNEP-WCMC Biodiversity Map Library. Cambridge, UK: UNEP-WCMC.
Even though these data sets are incomplete and of varying quality, they provide an indication of the extent of these habitat types around the world.
--------------------------------------------------------------------------------
Loss of natural habitats Mangrove and coastal wetland loss statistics by country, compiled from multiple sources. The inconsistent habitat classification schemes and the different time periods covered make assessing change difficult.
--------------------------------------------------------------------------------
Natural versus altered land cover within 100 km of coastline GLCCD (Global Land Cover Characteristics Database), Version 1.2. 1998. Loveland, T.R., B.C. Reed, J.F. Brown, D.O. Ohlen, Z. Zhu, L. Yang, and J. Merchant. 2000. “Development of a Global Land Cover Characteristics Database and IGBP DISCover from 1-km AVHRR data.” International Journal of Remote Sensing 21(6-7): 1303–1330. Data available on-line at: http://edcdaac.usgs.gov/glcc/glcc.html.
Summary of International Geosphere-Biosphere Programme land cover classes for land areas within 100 km of coastline. The coarse resolution (1km) and the classification scheme which focuses on terrestrial systems does not adequately capture the complexity of the coastal zone, but provides an indicator of the modification of coastal habitats.
Human population within 100 km of coastline CIESIN (Center for International Earth Science Information Network), International Food Policy Research Institute, and World Resources Institute. 2000. Gridded Population of the World, Version 2. Palisades, NY: CIESIN, Columbia University. On-line at http://sedac.ciesin.org/plue/gpw.
The original data sources are national population censuses by administrative district. Year of census and resolution vary. Estimates are standardized for 1990 and 1995.
Disturbance to benthic community--distribution of trawling grounds McAllister, D.E. J. Baquero, G.Spiller, and R.Campbell. 1999. “A Global Trawling Ground Survey.” Unpublished paper prepared for PAGE.
Partial global summary of trawling grounds in 24 countries by McAllister et al. (1999) executed for this study. Does not show the intensity of trawling within each area.