Extreme events are predicted to become more frequent with climate change. On the coast, sea level rise and increasing storminess will put further pressure on infrastructure that seeks to limit shoreline erosion and flooding. Salt marshes are vegetated ecosystems that occur in the intertidal zone. They are important regulators of the coastal environment, since they protect the coastline against floods and erosion. Efforts are made by governments to plan ahead for the future under climate change and to protect important ecosystems such as salt marshes. Current predictions, however, lack in evidence on how resilient marshes are to climate change. Some marshes undergo sudden changes or state shifts – dramatically declining or expanding in area or shifting their distribution, for instance from one part of an estuary to another. The causes for such shifts may not be known, although some are thought to be natural. This uncertainty presents a challenge to shoreline management planning. Currently, there are no predictions as to when or where state shifts will occur. The inability to account for such long-term ecosystem dynamics is the main knowledge gap that hampers the effective use of coastal ecosystems for flood defence.
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