The sustainable carbon management of British blanket peatlands: a case study on Dartmoor

by Lauren Parry– 17th November 2010.

Lauren Parry: ‘the sustainable carbon management of British blanket peatlands: a case study on Dartmoor’

Amory Building, Exeter University, Wednesday 17th November 2010

An audience of twenty-six was treated to a most impressive and interesting lecture by Lauren Parry in the Amory Building of Exeter University, following refreshments beforehand.

Lauren graduated from Leeds University in 2005 with a First Class Degree in Geography. Since 2007 she has been working on her PhD on sustainable carbon management, at both the University of Plymouth and the University of Exeter. As well as being in receipt of a Great Western Research studentship (funded by the South West Regional Development Agency), her research has been co-funded by the Duchy of Cornwall, Dartmoor National Park Authority, Natural England and the National Trust.

Lauren began by acknowledging the very considerable support she has received from her supervisor, Dan Charman.

It has been estimated that peatlands consist of approximately 50% carbon. Within a British context, Scotland contains the largest area of peatlands. The Dartmoor blanket bog peat is at the southern limit of its distribution in western Europe.

Peat can be subject to water loss due to evaporation, fluvial erosion, and gaseous and aeolian (wind) losses. Grazing, burning and draining can all affect  peat. In general, the input of carbon into peat is greater than output, i.e. peat stores carbon.

Quantification and mapping (both extent and depth) have been major parts of Lauren’s work. She has examined both deep and shallow peats, and showed a wonderfully detailed map of the distribution of different types of peats on moorland Dartmoor. Dartmoor’s blanket peat covers some 12,000 hectares but is itself very varied and complex, with many processes taking place beneath the surface. There are about another 18,000 hectares of shallower peats on moorland Dartmoor.

Using 1000 sampling points Lauren measured a peat depth ranging from 3.3m to a few centimetres. The average depth of blanket peat was about 0.80m but elevation and slope are key factors. Her most detailed work has been within the upper reaches of the Plym valley (on National Trust land), but overall her work has covered much of Dartmoor. Previous work was not so precise, with data derived from 1 km intervals.

Lauren has also taken 30 cores of blanket peat.

Her data allows her to estimate that Dartmoor contains some 9.7 Mt (1 x megatonne = 106, i.e. 1 million, tonnes) of carbon stored in its peat, which is the approximate equivalent of some two years of emissions by the agricultural industry. Most of this (7.22 Mt) is stored within the blanket peat i.e. 629 tonnes per hectare. The Forest of Dartmoor alone contains some 5.95 Mt (562 tonnes per hectare).

At Blackbrook, visited by members of the Dartmoor Society earlier this year, the peat contains roughly 583 tonnes per hectare.

On the blanket peat, Lauren chose three different sites to monitor:

a) Maiden Hill (between the headwaters of the Walkham and Cowsic rivers)– a ‘control’ site, seemingly unaffected by digging or burning;

b) Blackbrook Head (4 km N of Princetown)– a site with evidence of draining/digging – there are some 30km of dug drainage ditches here within a 100ha area;

c) Black Hill (1km S of Cranmere Pool) – a site with recent burning.

At each site Lauren took 5 x 30cm monolith cores for analysis. Spheroidal Carbonaceous Particles could pinpoint the peak of industrial emissions in 1975, and radio isotope dating could pick out the atomic bomb tests of 1963 and natural fallout of radionuclides.

At Black Hill she was able to measure that the peat accumulated some 55gm of carbon per annum, whereas at Maiden Hill the accumulation rate was 105.2 gm p.a., indicating that burning can reduce the rate by 50%. At Blackbrook Head the historic drainage had no effect on the carbon accumulation rate/sequestration (i.e. ‘the process of removing carbon from the atmosphere and depositing it in a reservoir’, in this case blanket peat).

Lauren also established ten dip wells to measure hydrology.

Lauren concluded that in the localised area surrounding the drainage site carbon accumulation was not significantly impacted by drainage. However, the success of drainage systems in drawing down water table can vary with age and topography surrounding the drainage. She suggests more research is needed in other topographical situations.

Lauren’s talk was illustrated with a superb set of slides, many of them technical, but no less fascinating. ‘Kriging’ was a term new to many – (a definition given on Wikipedia is ‘ a group of geostatistical tecnhniques to interpolate the value of a random field…at an unobserved location from observation of its value at nearby locations’).

In summary, the audience learnt that:

  1. The variety, extent and depth of Dartmoor peat has been mapped in detail for the first time.
  2. Its carbon content has been measured/assessed for the first time.
  3. The rates of absorption/release of carbon have been measured and quantified for the first time.
  4. The effects of burning and/or draining have been quantified.
  5. Specific historic events can be recognised in the peat (e.g. 1963 A-bomb testing; 1975 peak of emissions).
  6. Hydrology has been measured.

The overwhelming impression was that Lauren’s pioneer work would prove to be the basis of future work for many years to come, but that we were still only at the start of understanding the remarkable data that peat contains.

Everyone was extremely grateful for the opportunity to hear about this exciting and highly professional work which is exactly the sort of thing the Dartmoor Society wishes to encourage.

Tom Greeves

Leave a Reply