Carbon Storage and Distribution in a Temperate Saltmarsh –
A case study of the Ribble Estuary, UK

Abstract

Temperate saltmarshes serve as important stores of blue carbon and climatic regulators, however little is currently known about the contemporary carbon storage capacities of UK saltmarshes. This study quantifies the carbon storage capacity of the saltmarshes in the Ribble estuary and analyses the influence of elevation, gradient and watercourse proximity on carbon distribution. The study specifically focusses on carbon stored within the ‘active section’ which is comprised of the above-ground biomass and surface organic layer, defined as the ‘active layer’ in this research. Overall, the findings indicate that 1.26 x 107 kg and 12.9 x 107 kg (3.s.f) of carbon is stored within the above-ground biomass and active layer sediment respectively, although carbon is unevenly distributed between the sub-environments that comprise the saltmarshes of the Ribble. Whilst elevation, gradient and watercourse proximity are recognised to exert an interconnected influence on sub-environment and carbon distribution, only gradient and watercourse proximity were found to be statistically significant. In all sub-environments watercourse proximity exhibits a standardised influence between 50.1% and 72.0% greater than gradient. The overall distribution findings rebuke the simple elevation ramp model of distribution and support the theory that saltmarsh sub-environment and carbon distribution is controlled by a multitude of interconnected ecogeomorphological factors. The study also highlights the overall active section carbon storage capacity of the Ribble saltmarshes could decrease by 23.8%, 30.7% or 30.9% of the 2012 capacity by 2100 under the respective RCP 2.6, 4.5 and 8.5 (50th percentile) sea level rise scenarios. There is also the potential for greater degradation and carbon loss to occur as result of sea level rise driven headward expansion of creeks given the significant influences of watercourse proximity and gradient on sub-environment distribution. Therefore, it is important future shoreline management policies are adapted to limit future degradation in order to allow the saltmarshes of the Ribble to continue to act as an important store of blue carbon.