The coastal zone is the long narrow interface between the land and the ocean; it is a naturally dynamic zone which is subject to increasing human use. A 100 km wide coastal zone occupies 19.2% of the total earth’s land surface – excluding Antarctica. Yet, coastal population density in those parts of this zone below 100 m elevation is estimated to be 112 people per km² – about three times the global average. Around 23% of the 1990 global population live in this zone (i.e. about 1.2 billion people), which is considerably lower than various earlier estimates of 40–60%. However, what is important is not the exact population or population density, but the undeniably rapid demographic growth in this narrow zone – be it in the dominating rural areas and the small to medium-size cities or in the many coastal mega-cities – which will continue to concentrate human activities in the coastal zone. 

This will impose disproportionate pressures on the earth system. The coastal landscape and coastal seas are influenced by human activities both in the coastal zone and in river basins. Alterations to upland areas are causing marked changes in the timing, flux and dispersal of water, sediments, nutrients and contaminants to the coastal zone. In addition to the changes in upland areas and their downstream consequences, many other human activities impact upon the coastal zone, including:

• Building of shoreline engineering structures, ports and urban developments

• Harvesting, often over-harvesting, of marine resources

• Loss of traditional food resources and cultural value for indigenous people

• Increased use of marine space

• Increased water-borne and atmospheric pollutants from industries and urbanization

• Modification of the type and quantity of coastal discharges from surface and groundwater flows

• Loss of coastal wetlands and other valuable ecosystems through land use change

• Modification of habitat structure and functioning due to introduced species

The consequences of these alterations are far reaching and affect societal and global functions, including changes in ecosystem health and biodiversity, vitality and productivity of coastal ecosystems, coastal stability and morphology, and the fate and distribution of particulate and dissolved river loads in coastal and shelf waters. All of these tend to diminish the options for sustainable development and increase the uncertainty in coastal management.