A revisit to previous research into the current and potential climate change mitigation effects of environmental stewardship (BD5007)

Abstract

Environmental Stewardship was introduced to build on the already successful Environmentally Sensitive Areas (ESA) scheme and the Countryside Stewardship Scheme (CSS). Although primarily engaged with resource protection such as soil and water and the enhancement of biodiversity, the alterations in land use that are undertaken during the implementation of ES options do have implications for climate change mitigation. Defra project BD2302 quantified greenhouse gas (GHG) mitigation (excluding displacement of production) within Environmental Stewardship (ES) and established the potential for delivery of climate change mitigation under the scheme. A comprehensive review of this work has now been undertaken to ensure that the scenarios continue to be robust and that the parameters included within the calculations are optimal. Particular attention has been given to the highest ten performing options from BD2302. The previous Life-cycle Assessment (LCA) approach used in BD2302 has been repeated with improvements to the method to quantify the net GHG emissions, either positive or negative, under each ES option relative to a baseline typical arable or grassland system. Improvements to the method include accounting for the impact of soil type, timing and method of incorporation on nitrous oxide emissions from livestock manure application, livestock dietary constituents on enteric methane production and methane during manure storage, and additional soil organic carbon equilibriums. Baseline scenarios have been reviewed and updated, and new baselines created as necessary. Options and option supplements not previously considered in the original BD2302 project have also been reviewed and included where relevant. An analysis of new ES options introduced since completion of BD2302, including the Uplands stand of the Entry Level Stewardship (ELS) scheme, have been conducted. Management scenarios have been constructed, and a comparison of the current management requirements of all ES options with the previous management specifications undertaken, differences highlighted, and then incorporated into the new management scenarios. The net GHG balance of each evaluated ES option using the revised baseline scenarios, management scenarios where applicable, and revised emission factors and improved method has been calculated for both the original BD2302 option management scenarios and current ES option management scenarios. A direct comparison between the two has identified no significant impact on GHG emissions from alteration to the management specifications of ES options since completion of BD2302. The greatest impact has arisen where baseline scenarios have been modified, namely from temporary grassland to permanent grassland as was deemed necessary for selected options on grassland. The newly introduced ES options have further reduced agricultural GHG emissions excluding displacement of production (EDP )). Certain new options, for example winter cover crops, achieve an emissions reduction without the removal of land from its original land use and from agricultural production (have minimal production displacement risk). The overall impact of minimal displacement risk options on agricultural greenhouse gas emissions has been estimated, in addition to the emissions reduction where displacement may be beneficial (from deep cultivated peat soils for example). In total, ES achieves a mean annual greenhouse gas emission reduction(EDP) of 4 Mt CO2e year-1, of which 68,000 t CO2e year-1 is estimated to result at negligible production displacement risk.