The Earth's climate is warming and sea levels are rising around the globe, flooding and eroding our coasts. One important type of coastal environment that is at risk are saltmarshes. These are vegetated tidal flats that are tucked away in sheltered embayment’s, where there is a gradual transition between the land and sea. They also occur in more exposed locations where they form a natural defence against the encroaching sea. Saltmarshes are also valuable because the plants that grow on them absorb carbon at a very fast pace, much faster than, for example, trees. Saltmarshes are therefore useful in taking carbon out of the atmosphere and storing it away. Because carbon in the atmosphere is important in controlling the Earth's temperature, storing carbon in the ground can help reduce climate change.

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The vegetation on a saltmarsh is close to the level of the highest tides. Every time the tide comes in, a thin layer of mud is deposited on top of the saltmarsh surface. Over time, the saltmarsh mud gets thicker, but it can only increase in thickness if sea level goes up. So in that sense, sea-level rise can be beneficial to saltmarshes, because if the amount of mud gets thicker they can perhaps store more carbon and reduce climate change further! It is a new idea. Whether it is actually true is what we want to find out. As always, things aren't so simple. Apart from sea-level rise, there are other factors that can play a role in changing the amount of carbon buried in a saltmarsh, for example the tides, the availability of sediment, the types of plants, and whether the marsh is sheltered or exposed to the sea.

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