Wicken Fen, Cambridgeshire
Wicken Fen is a small remnant of rare alkaline fen habitat. The National Trust is buying patches of the surrounding arable farmland and restoring it to a wetland mosaic, aiming to grow the fen from 170 ha to over 5000 ha by 2100. TESSA was used to evaluate the benefits of this initiative by comparing a block of restored wetland with adjacent unrestored arable land. Carbon storage and greenhouse gas fluxes were estimated using literature values for degraded and restored peat grasslands, and recreation value was estimated using travel cost and visitor expenditure, gathered through visitor surveys. The results suggest that restoration would provide net benefits worth $199 ha/y, for a one-off investment of $2320/ha. The estimated loss of arable production worth $2040/ha/y is offset by estimated gains of $671/ha/y in nature-based recreation, $120/ha/y from grazing, $48/ha/y from flood protection, and $72/ha/y from reduced greenhouse gas emissions, as well as a reduction of $1325/ha/y in management costs. .
Ouse Fen and Fen Drayton, Cambridgeshire
Ouse Fen and Fen Drayton Lakes are two RSPB wetland reserves created by restoration of gravel extraction pits, which are important for rare birds such as the Bittern. Ouse Fen was originally going to be restored for agriculture but is now being gradually restored to wetland through designing the topography and planting reeds. Fen Drayton Lakes has already been restored to wetland but contains a mix of non-intervention areas that were left to colonise naturally and intervention areas that were re-profiled and replanted. TESSA was used to compare the benefits of these sites under their current use and under alternative restoration scenarios: agricultural use (for Ouse Fen), and either 100% non-intervention or 100% intervention (for Fen Drayton Lakes) .
A preliminary scoping study involving stakeholder consultation identified the main ecosystem services provided by the sites as being carbon storage and sequestration, flood protection, nature-based recreation, agriculture (under the alternative scenario), grazing (used for managing the grassland areas) and fishing. Literature values were used for carbon stored in soils and vegetation and emissions from livestock and arable crop production, and the Farm Business Survey was used to estimate returns from agricultural use. Recreational value was determined using visitor questionnaires and then estimating travel cost and visitor expenditure. Flood mitigation was estimated as the water storage capacity above and below ground. At Ouse Fen, the wetland restoration increased the value for recreation. At Fen Drayton, recreational value was greater for the non-intervention state than the intervention state, though there was clear segmentation with some visitors preferring one state and other visitors preferring the other, suggesting a mix of restoration types would create greatest value. In both cases there were trade-offs between food production, recreation, greenhouse gas emissions and restoration costs.