Impact of the drought in England on carbon dioxide fluxes from lowland peatland in the East Anglian fens across a land use gradient

Large parts of South-Eastern and Eastern England have recently been declared to be in a state of drought. On 20 February 2012, Environment Secretary Caroline Spelman declared a state of drought, citing concerns about the drinking water supply, diminishing ground water resources and possible water use restrictions. The drought has led to visible impacts on East Anglian lowland peat soils in the fens, where road surfaces have started to crack due to peat contraction. The drought creates an unexpected scientific opportunity to measure its impacts on greenhouse gas emissions from fenland ecosystems. This grant will establish a measurement station on an agricultural field near Wicken Fen, Cambridgeshire, to measure greenhouse gas fluxes.

We will test is whether the drought conditions lead to enhanced carbon dioxide emissions from lowland peatland, and whether wetland restoration increases resilience against drought in comparison to agricultural land.

Besides the direct impacts of the drought on infrastructure and water supply, there is an urgent need to study the impacts on the carbon cycle and radiative forcing. Predictions by climate models generally suggest an increasing frequency of previously rare extreme events. As a result of the increase of global average temperature it is thus reasonable to expect that prolonged dry conditions like those currently experienced this spring in England could happen more often. It is imperative to start recording direct measurements of carbon fluxes during drought conditions to have quantitative evidence of the carbon impact of drought conditions.
Lowland peat soils in England occupy 958 km2, store large amounts of carbon and are subject to very high levels of land use pressure because of their high agricultural productivity. To date, most measurements of CO2 and other greenhouse gas (GHG) fluxes from UK peatlands were collected in upland blanket bogs. There are doubts whether the blanket bog GHG fluxes can simply be assumed to apply to lowland fenland. In England, nearly all fenland has been drained and cultivated for intensive agriculture. In the fens of East Anglia, this has resulted in rates of peat loss of about 1 cm yr-1.
Natural England (2010) were the first to provide initial GHG flux emission factors for English peat soils. According to this report, degraded English peats alone are thought to emit around 3 Mt CO2-eq yr-1. Recent peatland studies for DEFRA and JNCC have highlighted the high degree of uncertainty in GHG flux estimates for lowland peats and in particular for fens.
At the Wicken Fen National Nature Reserve near Cambridge, the Centre for Ecology and Hydrology (CEH) and the University of Leicester (UoL) have installed two eddy covariance towers. The measurements of CO2 fluxes at the natural fenland site in Sedge Fen (operated by CEH) and the wetland regeneration site at Bakers Fen (operated by UoL) are providing important time-series data that allow inferences on the carbon balance. These two flux towers are the only measurement stations in lowland peatland in the UK.

The gap in current measurements is in the agriculturally used fenland area.

The purpose of this NERC urgency grant is to fund technical and research staff time to collect eddy covariance CO2 measurements over agriculturally used fenland in the growing season of 2012 and beyond to record the impacts of the current drought and the recovery of CO2 fluxes to a more usual state.

Who will benefit from this research?

Beneficiaries from this research include the National Trust, who is currently undertaking a very ambitious re-wetting programme in the Wicken Fen region, with plans to extend the regenerated fenland from Wicken all the way to Cambridge.

Policy makers, DECC and DEFRA will benefit from the numerical quantification of CO2 emission factors from agriculturally used lowland peatland, and from knowlegde of the impacts of a drought on the emissions. They will also benefit from scientific evidence to what extent wetland restoration in lowland peat regions can make these ecosystems more resilient against droughts. The outcomes have direct land use, climate and environmental policy implications. A letter of support from DEFRA is attached.

Land managers will potentially benefit from this research, if the findings support the eligibility for carbon emission reduction certificates if land use is switched from agriculture to semi-natural wetland.