Grassland plants disappear due to nitrogen, study suggests
A study that has already proven the damage that nitrogen pollution inflicts on grassland biodiversity in the UK is now providing evidence that the effect is in fact Europe-wide. European
scientists have been investigating 70 grasslands in nine countries for the past year. The first field results seem to corroborate the pattern found in the UK: a direct link between species loss
and long-term deposition of nitrogen.
‘The loss in Great Britain is much larger than people had imagined,’ Nancy Dise from Manchester Metropolitan University says. ‘It is almost 25% of species at the average deposition rate.’ The
species hit hardest are wildflowers and other plant species with broad leaves. Grasses, on the other hand, do not appear to be affected to the same extent. ‘If this is occurring across Europe,
it will be an important find,’ Dr Dise continues. A find that the scientists think might confirm the need to change current policies to protect ecosystems.
Agriculture and fossil fuel emissions are the principal human activities that create nitrogen. In the UK, for instance, the rate of deposition per year may range from five to 35 kg per hectare,
with the highest rates occurring in densely-populated areas. The initial study showed that one plant species was lost for each additional 2.5 kg of nitrogen deposited per hectare and year.
The aim now is not only to gather similar data for other parts of Europe; scientists are also trying to find a way to maintain species richness in spite of nitrogen deposition. ‘If we find [a
way], we can offer a management strategy for nature conservation,’ David Gowing from the Open University in Milton Keynes explains. One possible approach could be extra mowing and grazing, so
called ‘biomass stripping’.
Furthermore, the researchers hope to be able to predict future developments. ‘Nitrogen deposition in Europe probably peaked in the 1990s, and is coming down now, in many places,’ Dr Gowing
points out. ‘Having been accumulating nitrogen for 40 years, we might be near the edge of a cliff where communities will suddenly change. Perhaps we will be able to say: you have another five
years of accumulating at this rate, so now is the time to act.’
The project that started out as a PhD study in the UK has been extended to Germany, France and the Netherlands. It is investigating nitrogen effects on a wide range of grasslands across the
entire Atlantic side of Europe, as ‘the low countries and northern Germany are the epicenter of European nitrogen deposition’. The study is part of the project ‘Biodiversity of European
grasslands – the impact of atmospheric nitrogen deposition (BEGIN)’ funded under European Science Foundation’s EuroDIVERSITY Programme.