With every rise and fall of the tide, saltmarshes gradually accumulate organic-rich soils, infused with rotting leaves and seaweeds from land and sea. This material becomes trapped in the soil, creating stores of organic carbon.
Marshes are not only important stores of carbon, but the continuous sequestration of organic material means that marshes are actively trapping carbon, helping to mitigate the Climate Crisis. Preserving the loss of carbon already stored and ensuring that marshes continue to capture carbon is one of the most practical actions we can take to limit global warming.
To help coastal managers determine the amount of carbon held within marshes across Great Britain, the C-SIDE project launched the CarbonQuest Citizen Science project in August 2019. CarbonQuest sought to measure the amount of carbon stored in GB saltmarshes.
We approached various nature conservation groups asking for volunteers. Members of the Wildlife Trusts, National Trust, RSPB and more all took part, making a 100-strong team that gathered samples from the Solent to the Shetlands, from Barmouth to Yarmouth.
Each volunteer was sent a package containing survey equipment and instructions. Syringe tubes with the end cut off worked nicely as chambers for taking 30 cm soil cores. Five colour-coded syringes were sent to each volunteer.
Volunteers were then asked to take soil cores along a transect, going from land to sea, across a local saltmarsh. Each syringe tube was photographed in the soil, so that the vegetation visible in the image could be matched with the properties of the soil, and the location of each soil core could be noted by the GPS coordinates saved by the smartphone when taking photos.
Over 500 soil samples were sent back to the lab in St. Andrews University, where our colleagues diligently prepared the samples and analysed how much carbon they held. This represents the largest soil carbon dataset to date.
We took the area of each marsh and multiplied it by the carbon content of soil cores, to provide an inventory of carbon stocks across Great Britain. We were then able to identify carbon hotspots across Great Britain, and begin to explore why some areas are richer in carbon than others. Our aspiration is to have government organisations incorporate these findings into natural capital calculations.
This project highlighted the important role of Citizen Science in enabling large-scale carbon surveys to take place. Thank you to the dedication of all the CarbonQuest volunteers that enabled this work to be completed