A continuous covering of bog, needing high humidity and rainfall, mostly comprising peat; only steep slopes and rocky outcrops are dry. Huang (2002) J. Biogeog. 29, 2 finds that human impact was the dynamic force responsible for the destruction of the woodland and the formation of blanket bog in upland Ireland. In the UK Peak District blanket bog has suffered a decline in species diversity as a result of ‘air pollution, overgrazing, inappropriate or accidental burning, peat extraction and past drainage’ (Blanket Bog Action Plan 1, section 6. 4).