Atmospheric nitrogen deposition is silently ravaging our plant communities and the precious habitats they underpin, says Plantlife, Europe's largest charity dedicated to wild flowers and other plants, in a recent report entitled We Need to Talk About Nitrogen. Nitrogen deposition takes place when nitrogen emissions from transport, power stations, farming and industry are deposited (fall back down) into the natural environment directly from the air or in rain.
The report highlights that 90% of all nitrogen-sensitive habitats in England and Wales – such as heathlands, acid grasslands and sand dunes - are receiving deposition at higher levels than they can tolerate. As a result, plants that need low nitrogen levels are declining. Over a third of our flowering plants prefer low nutrient conditions and are therefore at threat, including harebell (Campanula rotundifolia), which recently was classified as near-threatened in England, and bird’s-foot trefoil (Lotus corniculatus), which supports more invertebrates (160) than any other herb.
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The OPAL Air Survey uses lichens to assess the potential local impact of nitrogen deposition. This is particularly important as many lichen species are very sensitive to nitrogen, including eyelashes treebeard lichen (Usnea florida). Plantlife’s report emphasises both the need for policies to reduce the release of nitrogen to the atmosphere and the need to raise public awareness of the threat posed to sensitive species. The OPAL Air Survey provides a great way of increasing people’s awareness of the impacts of nitrogen deposition.