In the air quality directive (2008/EC/50), the EU has set a critical level for nitrogen oxides (NOx) for the protection of vegetation within the zones designated by member states: the NOx annual mean value may not exceed 30 micrograms per cubic metre (µg/m3).
EEA standard re-use policy: unless otherwise indicated, re-use of content on the EEA website for commercial or non-commercial purposes is permitted free of charge, provided that the source is acknowledged (http://www.eea.europa.eu/legal/copyright). Copyright holder: European Environment Agency (EEA).
in your garden or park by piling up some logs in a secluded corner. These will provide shelter for hedgehogs, frogs and toads. If you half-bury the bottom logs in the soil, you will also encourage stag beetles as they are fond of rotten wood. A pile of stones will also provide shelter to a range of insects and spiders.
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