Keeping above the waves? The response of coastal freshwater peatlands to sea-level rise.

Project Background

There is considerable interest in how coastal saltwater ecosystems might adjust to sea-level rise and whether they will accrete rapidly enough to maintain their relative position in the tidal prism. This interest has arisen because of the importance of salt marshes and mangroves as natural coastal defences and as regionally- and globally-important (blue) carbon stores. Significantly less attention has been given to coastal freshwater wetlands, in particular peatlands such as floodplain fens. Sea-level rise caused by climate change is a potential major threat to these coastal freshwater wetlands. The ingress of saline water or higher groundwater could destroy their existing plant communities and their carbon sink function. In addition, inland areas currently protected by these wetlands may become more prone to flooding. There is some evidence that such wetlands have in the past increased their rates of peat accumulation in response to rising sea levels. However, the mechanisms involved are poorly understood, and without that understanding we cannot predict their likely response to future, rapid, increases in sea level. Understanding freshwater wetland response to sea level rise is a priority for policymakers and land managers as they adapt for a warmer world. The work has international relevance, with a large number of at-risk low-lying wetlands around the world. It will help indicate where to prioritise management efforts and may also show where new peatlands might form as shorelines move inland.

Project Aims and Methods

To address this critical research gap, this project will use a past-present-future approach, combining palaeoecological, process-based, and modelling work to understand the response of coastal freshwater peatlands to sea-level rise. The study will focus on two contrasting UK sites: Cors Fochno (an estuarine ombrotrophic bog in mid-Wales) and Wheatfen (a floodplain fen in Norfolk). Specifically, the project will involve: i) analysis of peat cores taken from both sites to understand their response to periods of past sea-level rise; ii) data collection to understand how current process and carbon accumulation rates adjust to hydrological and salinity changes; iii) modelling work using Met Office sea level projections in areas of freshwater peatlands, and the DigiBog peatland model to simulate past and future responses of the peatlands to changes in both climate and sea level. Wheatfen has been set up as an 'ecohydrological observatory' by members of the project team, and recently-collected datasets on fen water levels and saline surges are available.