Our current level of long-term and comparative information on estuaries in many cases prohibits objective
determination of the status and trends among these ecosystems. The way to resolve this situation is to
develop and evaluate estuarine environmental indicators that will permit objective and meaningful
evaluation of estuaries. However, this effort far exceeds the ability of one or a few well-intentioned
Estuaries are areas of high productivity, crucial in the life histories of many fish,
invertebrates, and birds, for example, and the sustainability of estuarine biodiversity
is vital to the ecological and economic health of coastal regions. On the other
hand, estuarine ecosystems are exposed to toxic anthropogenic effluents transported
by rivers from remote and nearby conurbations and industrial and agricultural concerns.
Defi ning, gathering, and disseminating international statistics is a collective effort of many people and
organizations. The indicators presented in World Development Indicators are the fruit of decades of work
at many levels, from the fi eld workers who administer censuses and household surveys to the committees
and working parties of the national and international statistical agencies that develop the nomenclature,
classifi cations, and standards fundamental to an international statistical system.