Energy and food production have resulted in large increases of ammonia and nitrogen oxide emissions to the atmosphere on a global and regional basis, with subsequent increase in Nitrogen (N) deposition. There are now large regions of the world where average N deposition rates exceed 10 kg N/ha/yr, greater than an order of magnitude increase compared with natural rates. These rates are well in excess of the critical loads that have detrimental impacts on receiving ecosystems. Given the growing importance of the atmosphere in Nr distribution, it is critical to get a better understanding of the link between nitrogen deposition and biodiversity loss, hence the development of the ‘nitrogen deposition’ indicator.

The indicator is applicable at local, regional and national scales.

The indicator is generally presented as maps of N deposition. Additional presentations integrate N deposition with maps of critical loads for ecosystems.

Estimated N deposition from global total N (NOy and NHx) emissions, totaling 105 Tg N y−1. The unit scale is kg N ha−1 y−1, modified from the original units (mg m–2 y–1)

Source: Galloway et al., 2008

Interpretation of the indicator is straightforward. The larger the deposition of nitrogen from the atmosphere, the greater the potential for negative impacts, including biodiversity losses on receiving ecosystems.

Future developments will occur on two fronts—improving our knowledge of nitrogen deposition to regions of the world, and improving our understanding of the links between nitrogen deposition and biodiversity loss. Both of these topics will be addressed at the upcoming Workshop on N Deposition, Critical Loads and Biodiversity, to be held 16-18th November, 2009, in Edinburgh, UK.