The value of carbon sequestration by saltmarsh in Chichester Harbour, United Kingdom

Following decades of habitat loss, carbon sequestration by coastal margin habitats has been recognised for its capacity to regulate atmospheric greenhouse gas concentrations. Chichester Harbour, an estuarine complex on the South coast of the UK, is used as a case study area in this paper. Saltmarsh habitat there has declined by 60.6% from 1946 to 2018. This downward trend is predicted to continue. Extrapolated from historic habitat loss, three future saltmarsh habitat area scenarios (worst-case, average loss, best-case) are used to estimate the net carbon sequestered by saltmarsh from 2018 to 2030. Only the best-case scenario predicts a positive net carbon sequestration. Two representative carbon prices (UK policy abatement cost, and the social cost of carbon) are applied to estimate the value of the net carbon sequestered. Discount rates of 2.3% and 3.5% are also applied. Average loss scenario values range from -£2,221,358.99 ±627,655.96 (abatement cost and a 2.3% discount rate) to -£986,303.19 ±278,684.84 (social cost of carbon and a 3.5% discount rate). This study is the first to examine non-use values in the area. Results generated here can aid in highlighting the benefits saltmarsh habitats provide, promoting its conservation, as valuations of coastal habitats are poorly represented in management.