This layer identifies areas of Ancient Woodland and Parkland from which NRW hold recent, auditable records of N-sensitive lichens. Not all lichens are sensitive to increased ammonia: the 62 species used to identify N-sensitive Ancient Woodland and Parkland are particularly sensitive and are important in the woodland/parkland ecosystem. Any area identified as sensitive in this GIS layer should be assessed using a 1µg/m3 NH3 Critical Level. Attribution statement Contains Natural Resources Wales information © Natural Resources Wales and Database Right. All rights Reserved. Contains Ordnance Survey Data. Ordnance Survey Licence number AC0000849444. Crown Copyright and Database Right.