Catchment restoration in the River Tamar catchment, UK : modelling agriculture, water quality and greenhouse gas emissions
It is known that agriculture makes a significant contribution to the total global anthropogenic emissions of greenhouse gases (GHG) and a recent UK Research Council report indicated that agriculture is responsible for approximately 8% of all UK GHG emissions, but that these estimates fail to consider “differences between farming practices or the effects of innovative approaches and policies”. Methane (notably present in livestock manures) and nitrous oxide (generated by the microbial transformation of nitrogen in soils and manures) have global warming potential values far in excess of that of carbon dioxide. Consequently, changes in agricultural land use and management may play an important role in achieving the UK Government’s target of reducing GHG emissions by 34% by the year 2020.
One aim of the RELU ‘Innovative Market-Based Mechanisms for Protection of Water Resources’ project is to assist development of a catchment restoration scheme in South West England. This includes appraising alternatives for agricultural land use change which will bring about water quality improvements in the River Tamar catchment, and modelling the likely impacts of such changes on GHG emissions. This paper focuses on the assessment of changes in surface water nitrates (NO3-) and nitrous oxide (N2O) emissions related to different land use and land management options. The objective is to determine which areas of the catchment to target for greatest benefit in terms of reducing these agricultural outputs and to assess the risk of pollution-swapping (and worsening of GHG emissions) such as swapping dissolved NO3- in water bodies for gaseous N2O from waterlogged wetlands.