In Brief
More Laughing Gas than Thought
The emission of nitrous oxide (laughing gas) from forest ground is at least twice the amount the Intergovernmental Panel on Climate Change (IPCC) had assumed so far. This is one of the key messages of the first assessment on nitrogen in Europe (European Nitrogen Assessment, ENA). The cause for this are reactive nitrogen compounds such as NH3 and NOx from agriculture, traffic and industry. Ranking third after carbon dioxide and methane, nitrous oxide is one of the main causes for the greenhouse effect. However, one kilogramme of nitrous oxide is approximately 300 times more conducive to the greenhouse effect than is the same amount of carbon dioxide.
The study shows, that some 2 to 6 percent of reactive nitrogen from the air are transformed to nitrous oxide, which in turn is emitted into the atmosphere from the forest ground. Up until now, the Intergovernmental Panel on Climate Change (IPCC) based its calculations on an amount of only one percent.
With regard to a forest area of 188 million hectare, the input of reactive nitrogen in the year 2000 increased by 1.5 million tonnes compared to 1860. This is an increase of approximately 8 kilogrammes reactive nitrogen per hectare of forest. The reasons for the increased atmospheric input of reactive nitrogen are the use of fertilisers in agriculture and the related emission of ammonia on the one hand, and the nitrogen oxide emissions as a result of the combustion not only of fossil fuels but also of biomass.
