Salt marshes are quiet heroes in our battle against climate change. Beneath their grassy surfaces, they capture and store significant amounts of “blue carbon”. Protecting and managing these ecosystems effectively could help reduce global warming. However, accurately measuring the amount of carbon stored in these areas has historically been complicated, costly, and time-consuming.
We explored a straightforward approach to predicting how much carbon salt marshes contain by using just two easily identifiable features: the type of plants growing, and the nature of the soil underneath them. By examining 23 different salt marshes across Wales, we developed a practical method to estimate how much carbon these wetlands store without the need for complicated equipment or extensive laboratory analysis.
Our study focused on two primary factors: plant communities, and soil type. Plant types give clues about the marsh’s overall condition and root structure, which is crucial for carbon storage. Some plants, like the rushes Juncus gerardii and Juncus maritimus, have dense root networks that hold onto more carbon. Other species, like Puccinellia maritima (common saltmarsh grass), tend to store less. Soil type is equally important. Non-sandy soils typically contain more carbon compared to sandy soils, as they retain organic material better.
The ‘sausage test’ assesses how well a soil sample can be rolled into a sausage shape and how it bends to determine soil type.
The simplicity of our method makes it broadly applicable not just in the UK, but potentially across salt marshes throughout Europe and similar regions globally. By enabling better predictions of carbon storage, we hope to raise awareness about the critical climate mitigation role these coastal habitats play and ensure they receive the recognition and protection they deserve.
We also created a simple tool that enables predictions of carbon stocks across large coastal areas called the Saltmarsh Carbon Stock Predictor (SCSP). We tested our approach by generating detailed maps for all salt marshes in Wales, revealing that these habitats can store as much carbon as certain forests and freshwater wetlands. This practical tool helped Natural Resources Wales rapidly assess the carbon storage potential of their salt marsh holdings, improving strategies for managing these valuable ecosystems.
Beyond helping experts, we also developed the Saltmarsh App. The App was a citizen science tool to easily estimate the carbon storage of a local salt marsh by observing its vegetation and soil characteristics. Sadly, we didn’t have sustained funding to keep the App updated, so it has since been removed from iOS and Android app stores.
In short, understanding the hidden carbon stores in salt marshes doesn’t always require high-tech tools – just a good look at the plants under your feet and a handful of soil.