As an interface between two major Earth system components - the land mass and oceans of the planet-the coastal zone is a particularly sensitive arena of global change. This paper reviews a set of interrelated challenges that are posed for the coast zone by climate change. What makes these issues particularly challenging is that climate change is but one driver. An example is sea level rise.

The "source" of sea level rise is only partly initiated within the ocean; the dynamics are strongly coupled to processes operating in upland contributing basins. The major contemporary source of sea level rise is thermal expansion. Yet long-term and more recent sea level rise expressed through changes in the world's ice sheets and continental glaciers; however, reservoir construction and groundwater depletion by humans add complexities to any estimate of the impending rates of change.

The importance of land mass-to-coastline linkages is exemplified well by analysis of delta systems, which represent a unique balance of forces originating in drainage basins and the ocean. For a sample of 40 globally distributed deltas we estimated contemporary and future effective sea-level rise, using a GIS-based approach that unites several features of the continental land mass, human population and land occupancy estimates, and elevation data sets in the coastal zone. Decreased accretion of fluvial sediment resulting from upstream trapping of sediment in artificial impoundments plus consumptive diversions of water used in irrigation is the primary determinant of effective sea-level rise for over 2/3 of the deltas sampled. Only 20% of the deltas showed contemporary sea level rise as the predominant factor. Extending these contemporary estimates of effective sea-level rise from 2000 through 2050 reveals that approximately 8.7 million people and 28,000 km2 of delta area in our sample will be impacted by inundation and increased coastal erosion if these conditions continue and in the absence of mitigative measures. The population and area impacted rise significantly when considering increased flood risk from storm surges. These results indicate that the combined impacts of decreasing sediment supply, anthropogenic-induced accelerated subsidence and eustatic sea-level rise have serious implications to human populations worldwide and will continue to be an issue well into the future.

This issue and other dimensions of land-ocean system are considered in the context of global environmental change.