Three to five times more carbon is stored in soils than in vegetation such as trees. The deep rooting strategies of meadow plants enhance the ability of floodplain soils to sequester and securely store significant quantities of carbon throughout the soil profile. Organic carbon within the top 10 cm of soil at North Meadow in Wiltshire was recorded as 109 tC·ha−1 and within the top 50 cm, as over 200 t/ha), a much higher value than reported for neutral grasslands. Recently published research showed that higher species richness increases the sequestration rate in grasslands.
The ability of floodplain meadows to trap sediments and export nutrients such as phosphorus through the annual hay cut is vitally important to the restoration of good ecological status to rivers. Hay meadows are a nutrient pump removing phosphorus from river systems. This is potentially a tool that can be used as part of the Government’s Nutrient Neutrality agenda, and in restoring natural processes to protect sensitive catchments from increasing nutrient loads. A single hectare of meadow can export 5 kg of elemental phosphorus from a river system every year through the hay crop, highlighting their potential as a nature-based solution to eutrophication.
We are keen to explore the opportunity for carbon and nutrient offsets to provide funding for floodplain meadows.
We would like the Climate Change Committee to consider the maintenance and restoration of floodplain meadows as a carbon offset activity. There is already strong evidence of the carbon benefits of grasslands - in the UK and internationally. Nevertheless, more research is needed, and some is already underway.
However, offsetting schemes, especially tree planting, currently pose a major threat to these precious habitats, partly due to a lack of understanding and awareness of the carbon and biodiversity benefits of grasslands. They are sometimes inadvertently destroyed or damaged by well-meaning woodland creation projects in inappropriate places.
A second, related risk is that areas of grassland most suitable for restoration into species-rich grassland are instead identified as sites suitable for tree planting, often because they are seen as unproductive agricultural land.
We are engaged in a number of projects that include collecting data in order to build a convincing and rigorous evidence base demonstrating the role floodplain meadows can play in carbon stewardship and nutrient related schemes.