A major goal of the Macronutrient Cycles Programme is to provide policymakers with the scientific understanding needed to develop management strategies and policy, and assess their impacts.

Our proposed work aims to contribute to this through a new strongly integrated analysis of C, N and P over long timescales and at sub-catchment-to-regional spatial scales, with climatic drivers included.

Thus, if the Integrated Model can be validated by faithfully accounting for current soil and water conditions, it will find acceptance as a valuable tool for long-term, large scale forecasting.

Timescales

How long will management or policy measures take to have effects? For example;

  • The response of surface water nutrient concentrations to mitigation measures (Nitrates Directive, Water Framework Directive);
  • Responses of natural and semi-natural ecosystems to reductions in N emissions under the Gothenburg Protocol, both biogeochemical, and with respect to biodiversity for which the project will provide new perspectives by considering temporal responses;
  • Rates of soil carbon storage and denitrification under different managements and land use (Climate Change Act, Low Carbon Transition Plan).

Spatial scale

By utilising the large number of environmental nutrient data for the UK as a whole, the project will significantly improve the representativeness of model simulations, and increase confidence in the generality of predictions. Of specific interest are;

  • Provision of a spatial modelling framework within which to assess and generalise the results of more detailed, smaller-scale studies. In particular, we propose to apply the Integrated Model to the river basins within which the three Defra Demonstration Test Catchments are located. We will run scenarios chosen in consultation with the research scientists involved, and with Defra. This will increase the value of the DTC results, set them in context, and permit upscaling.
  • Source apportionment. Our “terrestrial unit” approach partitions a catchment into different land areas, each of which is modelled separately, and then the riverine loads are derived. Nutrient sources (dissolved and particulate) are quantified, as well as losses by floodplain sedimentation. Therefore, the Integrated Model will be able to explore the effects of different management options, or of land-use change, on riverine loads and concentrations of C, N and P, and N : P ratios, relevant to the OSPAR convention and WFD. This tool could help us to understand which sources should be prioritised for control of macronutrients, and level of damage by source.

Multiple effects

These are highlighted by the Stakeholder Policy and Research Interest Document of the Macronutrient Cycles Programme, and this is an important issue with respect to both understanding the natural environment and its management and protection, especially through the Ecosystem Services approach, as laid out in the National Ecosystem Assessment. Our results should be useful in;

  • Understanding and quantifying the responses of soil and water carbon cycles to nutrient enrichment, and what will be the further effects of climate change. The Integrated model will simulate how increased productivity has altered soil C stocks and turnover times, and soil emissions of CO2, while considering riverine fluxes of dissolved and particulate organic carbon. Also accounted for are climate change effects, through altered productivity, decomposition rates, and hydrology. New insights at catchment and regional scales will contribute to carbon management and mitigation of greenhouse gas emissions, relevant to the Climate Change Act.
  • Complementary to the previous point, we can also address the important controls of carbon on nutrient behaviour, and the transition from dominance by organic forms of N and P to contemporary conditions under which inorganic forms of the elements often prevail. Our long-term simulations will thus shed new light on nutrient behaviour, relevant to terrestrial eutrophication, increased N2O emissions, altered groundwater composition, nutrient loads and ratios to surface waters, and thence to coastal seas. This perspective is needed to enhance mitigation strategies for diffuse nutrient pollution.
  • We will address the highly pertinent issue of the extent to which spatial relationships can be used as models for effects of changes in nutrient availability on terrestrial and freshwater biodiversity over time through the application of modelled biogeochemical output to some of the UK’s best long term ecological records, with particular relevance to conservation of Biodiversity Action Plan priority habitats.
  • We will be able to offer integrated regional-scale simulations of the responses of pools, fluxes and riverine loads of N and P to changes in climate, land-use, farming practice, management and atmospheric pollution. This information can underpin socio-economic analyses of the trade-offs between sustainable food production and environmental damage, building upon the EU Nitrogen Assessment.