TOWARDS A STRATEGIC APPROACH TO NITROGEN IN SCOTLAND

SUMMARY Nitrogen was first isolated by the Scottish chemist and botanist Daniel Rutherford in 1772. While he famously found that a mouse was unable to survive in a chamber of nitrogen gas, in the modern world, there is more concern over other harmful biological effects of nitrogen. Nitrogen is an essential element for plant growth but, globally, the greatly increased use and release of reactive nitrogen from human activity over the last century is driving significant ecological change with negative impacts on biodiversity, both in semi-natural terrestrial ecosystems and in coastal waters. Within Europe, humans have more than tripled the amount of reactive nitrogen in circulation, mainly through fertiliser use, in addition to fossil fuel combustion and biological nitrogen fixation. In Scotland, significant areas of semi-natural vegetation receive nitrogen from atmospheric deposition at levels above the critical loads where ecological impacts can be expected. Much of this deposition results from diffuse emissions of reactive nitrogen gases from agriculture and transport, as well as transboundary atmospheric nitrogen pollution from continental Europe. The increased amount of reactive nitrogen in circulation also impacts on social and economic prosperity. These impacts include limiting the capacity for further industrial nitrogen emissions, temporary closures of marine fisheries and bathing waters due to toxic blooms and increased treatment costs for potable water. Societal reactions to these problems tend to be sector-specific and media-specific (i.e. water, air or land). We examine the case for taking a more strategic view of the issue of reactive nitrogen in the environment, and propose a possible approach based on a national nitrogen budget for water, air and land. A key objective of taking a more strategic, cross-sectoral and cross-media approach is to identify the multiple benefits of nitrogen reductions and improved nitrogen management across media and sectors.