Impacts of long term drainage and agriculture on the carbon dynamics of fen peatlands in East Anglia, UK

Over the last 150 years, extensive reclamation of UK lowland peatlands for agriculture, particularly in the East Anglian Fens, has provided some of the most fertile land in the UK, but resulted in a peat depth loss of up to 4.8 m and a significant carbon (C) emission. A large portion of formerly deep peat is now classified as ‘wasted’ (peat depth ≤ 0.4 m). In the Fens, both deep and wasted peats are used for intensive arable agriculture. 

Arable cropland on peatland contributes an estimated 7,600 kt CO2e yr-1 to UK emissions (32% of peatland emissions from 7% of the peatland area). This estimate is derived from emissions data for deep peats. No data for wasted peats were available despite their significant land area. To improve the emission estimate, CO2 fluxes at an arable wasted peatland were measured over two years using Eddy Covariance. Additionally, aeolian erosion was measured from the wasted and compared to a deep peatland.

The average emission from wasted peatland was 676 ± 188.5 g C m-2 yr-1 over two years (812 ± 195.6 and 540 ± 181.4 g C m-2 yr-1). This was lower than the emission factor for deep peat, suggesting the need for a separate emission factor for wasted peat. Primary drivers of Net Ecosystem Exchange were Air Temperature and crop growth, with Soil Water Content and Vapour Pressure Deficit also identified as influencing factors.

Aeolian erosion of the deep peat site was 1525 (1170–1880) g m-2 yr-1. At the wasted peat site, 1401 (1324–1477) g m-2 yr-1 was transported onto and 995 (842–1233) g m-2 yr-1 off the field. Net field C losses were 0.75 (0.57–0.92) t C yr-1 from deep peat and 0.21 (0.18–0.26) t C yr-1 from wasted peat. Field cover and field boundary vegetation height limited erosion losses.