Studies raise concern about impact of nitrogen on environment An international group of scientists warns about the effects of excessive nitrogen emissions from food and energy production on the global ecosystem in two papers published in the journal Science. Man-made reactive nitrogen is accumulating in soil, water, the atmosphere and co... An international group of scientists warns about the effects of excessive nitrogen emissions from food and energy production on the global ecosystem in two papers published in the journal Science. Man-made reactive nitrogen is accumulating in soil, water, the atmosphere and coastal oceanic waters and contributing to the greenhouse effect, smog, haze, acid rain, coastal 'dead zones' and stratospheric ozone depletion, they say. The work was partly funded by the EU. 'The public doesn't yet know much about nitrogen, but in many ways it is as big an issue as carbon, and due to the interactions of nitrogen and carbon, makes the challenge of providing food and energy to the world's peoples without harming the global environment a tremendous challenge,' says Dr James Galloway of the University of Virginia, USA, who was involved in both studies. 'We are accumulating reactive nitrogen in the environment at alarming rates, and this may prove to be as serious as putting carbon dioxide in the atmosphere.' Nitrogen occurs naturally in the environment and it accounts for up to 78% of the Earth's atmosphere. In its inert form, it is harmless. The massive amounts of nitrogen and nitrogen compounds released during the mass production of fertilisers and burning of fossil fuels, however, are highly reactive. 'Nitrogen is needed to grow food, but because of the inefficiencies of nitrogen uptake in plants and animals, only about ten to 15% of reactive nitrogen ever enters a human mouth as food. The rest is lost to the environment and injected into the atmosphere by combustion,' Dr Galloway explains. A single nitrogen atom may create a cascade of events, upsetting the natural balance of ecosystems and ultimately affecting human health: For instance, a nitrogen atom deposited in a lake as nitric acid might kill fish and insects. It could then travel on to the ocean, where it can contribute to red tides - massive algal blooms - and dead zones. Eventually, the atom might end up in the atmosphere again, where, as the gas nitrous oxide, it contributes to the greenhouse effect and also destroys atmospheric ozone. Focusing on the impact of nitrogen on the world's oceans, one of the studies adds that although nitrogen as a fertiliser increases marine biological activity and thus raises the ocean's capacity as a carbon dioxide (CO2) sink by about 10%, at the same time this effect in turn produces harmful nitrous oxides (N2O). 'The natural nitrogen cycle has been very heavily influenced by human activity over the last century - perhaps even more so than the carbon cycle - and we expect the damaging effects to continue to grow,' Professor Peter Liss of the UK's University of East Anglia, who contributed to one of the studies, comments, stressing that reducing the use of nitrogen fertiliser as well as pollution from cars are the only solutions. 'It is vital that policy makers take action now to arrest this.' 'This fertilisation of the ocean by human activities has an important impact on the exchange of the greenhouse gases carbon dioxide and nitrous oxide and should be considered in future climate change scenarios,' states Professor Robert Duce, lead author of one of the papers from Texas A&M University. Dr Galloway agrees: 'We must soon begin to manage nitrogen use in an integrated manner by decreasing out rate of creation of reactive nitrogen while continuing to produce enough food and energy to sustain a growing world population.' The studies contribute to various projects funded by the European Commission under its Sixth Framework Programme (FP6), the European Science Foundation (ESF) and the European Cooperation in the Field of Scientific and Technical Research (COST) initiative.
