Other chapters in this book have been concerned with plant communities on saltmarshes and have stressed the variability in community composition both within and between marshes. While the physiological basis for the survival of saltmarsh plants in a saline, waterlogged environment is now established, the differentiation between species expressed in distribution patterns of species and communities is less clearly understood. Concentration on organisation at the species and community level is appropriate for testing hypotheses of a biogeographic or ecophysiological nature and may provide input towards an eventual synthesis of saltmarsh ecology but any such synthesis will also demand an understanding of processes operating at the ecosystem level. Knowledge of how saltmarshes function as ecosystems will be necessary for long-term management and for full understanding of the linkages between estuaries and saltmarshes. As Mann (1982) has argued ‘we shall never make good predictions about ecosystems unless we learn to observe ecosystems, and make testable hypotheses about them’.

The study of saltmarshes as ecosystems is still in its early stages. Compared to terrestrial systems the relative species paucity of many saltmarshes may simplify ecosystem studies; on the other hand, the intertidal nature of the habitat presents many practical problems.

While there have been many studies of particular processes, there have been few investigations which have adopted an integrative approach to the whole system. Many of the generalisations about saltmarsh ecosystems are based not on complete studies but on assumptions developed to fill the gaps between studies on particular processes.