Causes of degradation and erosion of a blanket mire in the southern Pennines, UK

This study investigates the causes of erosion and degradation of March Haigh, a blanket mire in the southern Pennines (UK), over a period of 160 years starting in 1840 AD. Peat samples taken from the site were dated using 210Pb; their humification and magnetic susceptibility were measured; and they were examined for pollen, plant macrofossils and microscopic charcoal. Stratigraphic correlation with a dated ‘master’ sample was achieved using indicators of air pollution (magnetic susceptibility) and climate (peat humification). The data were used in conjunction with documentary records to reconstruct past variations in grazing pressure, climate, moorland fires and air pollution. Three major vegetation changes have occurred on the moorland since 1840, namely: (1)the disappearance of Sphagnum spp. in the mid 19th century; (2)the replacement of Calluna vulgaris by Poaceae as the dominant vegetation type ca. 1918; and (3)a reduction in vegetation cover and consequent erosion ca. 1959. The results concur with the findings of other investigations of ecological change in the southern Pennines insofar as degradation of vegetation prior to the mid 20th century appears to have been caused by air pollution, climate change and fire. Following the removal of vegetation by a severe fire during the summer of 1959, unprecedented sheep stocking levels maintained the bare peat surface and thus precipitated extensive erosion.