The Badlands of Britain

The uplands of northwest England are dominated by the presence of blanket peat deposits, forming due to the accumulation of organic matter over time (Bragg and Tallis, 2001). British blanket peat accounts for approximately 15% of the global total blanket peat (Evans and Lindsay, 2010). The peatlands of the South Pennines are considered to be extensively degraded and have been referred to as "the badlands of Britain" (Tallis, 1997).

This degradation occurs in the form of extensive gully networks, incising deep into the peat surface (Evans et al., 2006). Evans et al. (2006) calculated that sediment lost from some South Pennine catchments via gullying was as much as 267 tonnes per kilometre2 per year (t km-2 a-1). This released sediment is being carried via gullies to reservoirs and water courses.

It is thought that changes in the vegetation cover of blanket mires have led to the initiation of gullying (Yeloff et al., 2005). These changes can come in the form of vegetation removal or subtle changes in species distribution.

With the South Pennines being situated directly between two major cities in the Industrial Revolution (Manchester and Sheffield), It is thought that these vegetation changes are the result of heavy metal pollution emanating from chimney stacks, metal smelting and more recently, auto-mobile emissions (Rothwell et al., 2007). It is thought that vegetation on blanket mires is particularly susceptible to lead pollution.

Over grazing in these areas can cause trampling of vegetation and the removal via feeding of excessive livestock numbers (Smith et al., 2007), which could lead to gullying. However, Smith et al. (2007) concede that present livestock density in the South Pennines are relatively low and are not likely to cause a notable change in vegetation cover.

Peat is rich in organic matter and therefore carbon. Gullying and removal of the peat in the South Pennines has the potential for blanket mires to make the transition from carbon sink to carbon source. Once again it seems that there is another significant positive feedback loop in the climate change model.

Note: Maybe I should rename this blog Feedback loops in Atmospheric Carbon!

See also this brilliant blog and resource: www.peatbog.org

  References

Bragg, O.M., Tallis, J.H., 2001. The sensitivity of peat-covered upland landscapes. Catena, Vol 42 p345-360.

Evans, M., Lindsay, J., 2010. High resolution quantification of gully erosion in upland peatlands at the landscape scale. Earth Surface Processes and Landforms, Vol 35 p876-886.

Evans, M., Warburton, J., Yang, J., 2006. Eroding blanket peat catchments: global and local implications of upland organic sediment budgets. Geomorphology, Vol 79 p45-57.

Rothwell, J.J., Evans, M.G., Allott, T.E.H., 2007b. Lead contamination of fluvial sediments in an eroding blanket peat catchment. Applied Geochemistry, Vol 22 p446-459.

Smith, R.S., Charman, D., Rushton, S.P., Sanderson, R.A., Simkin, J.M. and Shiel, R.S., 2007. Vegetation change in an ombrotrophic mire in northern England after excluding sheep. Applied Vegetation Science, Vol 6 p261-270.

Tallis, J.H., 1997. Peat erosion in the Pennines: the badlands of Britain. Biologist, Vol 44 p277-279.

Yeloff, D.E., Labadz, J.C, Hunt, C.O., Higgitt, L., Foster, I.D.L., 2005. Blanket peat erosion and sediment yield in an upland reservoir catchment in the southern Pennines, UK. Earth Surface Processes and Landforms, Vol 30 p717-733.