THIS SD-DIMENSIONS SPECIAL addresses issues related to the potential impacts of sea level rise on the world's coastal populations and agriculture. This is a "global" study mostly based on national data.

The literature confirms that indirect effects of sea level rise, as well as the potential impact of extreme events, may be more significant than direct effects in the future. In the absence of an accepted methodology for building long-term scenarios, two approaches are explored here: an analysis of a large database of extreme events that have occurred over the last 100 years, and an analysis of population statistics in relation to a national Vulnerability Index based on physiographic features and population density.

Recent historical data are examined to identify trends that could be extrapolated into the 21st century. This is achieved by separating those factors that are more specifically associated with the oceans - tropical cyclones, tsunamis - from other, more land-bound or population-bound disasters, such as droughts and epidemics. Despite the limitations of the data sets, some trends do emerge, but they do not necessarily point in the direction of greater property and population losses in the future owing to sea-caused disasters. Rather, they indicate that difficulties - independent of the global changes - will be relatively larger on land than along the coasts, and that the major component of life and property losses are associated with levels of economic development.

The "national vulnerability index" confirms that vulnerability - if considered at a global scale - varies considerably, over several orders of magnitude. In addition, the index exhibits a marked positive skew. Combined with changes in population concentrations and the positive skew of many climatological elements (such as wind and rainfall), as well as sea-level rise itself, this indicates that relatively greater disasters are likely.

The paper stresses that both the impacted system (population and coastal agriculture) and the extreme physical factors have their own dynamics, and that those dynamics are not independent. Some thought is given to the notion of "shock-waves", i.e. the repercussions at some distance from the rising seas.