Salt marshes, along with seagrass and mangroves, are known to be globally important carbon sinks. Salt marsh plants absorb CO2 from the air. Through photosynthesis, they use the carbon to build plant parts such as leaves and roots, i.e. organic biomass. Salt marsh plants produce a considerable amount of belowground biomass. This organic matter is persistent and only decays over a long period of time. Over time, some of the carbon-containing biomass is permanently buried in the marsh soil. Here, conditions are usually favourable for the preservation of the organic material, which can lead to carbon storage for thousands of years. In this way, salt marshes absorb CO2 from the air and store it as organic carbon in the soil - a mechanism that removes CO2 from the atmosphere and counteracts climate change. In addition, salt marshes act as a filter and trap for sediment and organic material that enters the salt marsh from outside. When water levels are high, salt marshes are flooded and the salt marsh plants literally fish out sediment and organic material from the water above them. Organic material in particular also contains carbon, which is then deposited in the salt marsh and later stored in the soil. The accumulation of carbon from sources outside the salt marsh also contributes to the role of salt marshes as carbon sinks.