Macronutrient cycles and climate change: key science areas and an international perspective

Human activities have doubled global cycles of Nitrogen (N) and Phosphorus (P) and elevated N and P have compromised ecosystem services through the degradation of natural resources of soils, freshwaters and marine waters with a subsequent loss of biodiversity. Elevated Carbon (C) levels in the atmosphere have been linked to global warming, with positive feedback mechanisms accelerating the warming process. In order to initiate nutrient control, both national and international mitigation measures have been implemented. However, many of these initiatives focus upon a single nutrient without considering cycle interactions. A sound understanding of processes and transformations involved in the interactions of macronutrient cycles is required to avoid inadvertently enhancing effects of one nutrient, during mitigation for impacts of another. Emerging research initiatives are addressing these research gaps, with programmes in the US (USGCRP) and the UK (Macronutrient Cycles) advocating integration between scientists and stakeholders, in order to deliver results directly to policy makers. Through these programmes the scales of nitrogen and phosphorus fluxes will be quantified, and a determination made of the nature of nutrient transformations in catchments under a changing climate and perturbed carbon cycle. The consideration of connectivity between multiple macronutrient cycles will help to minimise the threats to biodiversity, ecosystem dynamics, public water supplies and human health by improved management and better focused policy.