The peaty soils of Scarborough Carrs, in places up to 3m deep, formed in waterlogged ground where a Stone Age wetland landscape used to be some 10,000 years ago. Coined ‘Lake Flixton’ this watery environment, inhabited by Mesolithic humans was in fact part of a string of shallow water bodies, reedswamp and boggy woodland right along the Vale of Pickering. Over the millenia, deep fen peat deposits accumulated and the lakes gradually filled in. The open landscape of today with level fields divided by water-filled ditches has been created by over 200 years of land drainage for farming. The peat is evident in the sides of the ditches when they are cleaned out to keep them flowing, or in the dark colour of ploughed fields – giving rise to the local term ‘Black Land’. There are a number of reasons as to why it is important to conserve peatlands, for example they act as a sink for CO² and when they are degraded they release this back into the atmosphere, furthering the effects of climate change. It is also used to help us reconstruct the past as it preserves pollen, artefacts and fossils which act as clues to help build the picture of past environments and human land use. Read the post on The Carr’s Holocene sediments here.
A sensible estimate of the volume of carbon-rich peat in the Flixton Basin is 20 million cubic metres (assuming around 1000ha at 2m deep). Current estimates of carbon dioxide emissions from drained peatlands elsewhere would conservatively suggest (at 8 t/ha) around 8000 tonnes of CO2 emanating from the Flixton peatland every year as this organic soil steadily oxidises and shrinks. Sobering thought…
Research elsewhere quantifies typical carbon content of peat soils between 30 and 70kg per cubic metre. As a rough, ‘back-of-an-envelope’ calculation, assuming the above values, I would estimate the carbon stock of the Flixton Basin to be 600,000 – 1,400,000 metric tonnes. Wow! So a million tonnes of carbon, give or take. (Keep in mind this is only a portion of the Vale of Pickering, where peat depth and has been sampled in some detail, due to it’s intense archaeological interest in palaeolake Flixton)
If we estimate roughly that the total Vale of Pickering area is 500sq km, or 50,000 hectares, that is fifty times the Flixton basin area. Now, let’s be fair, Flixton is unusual in having almost pure peat of several metres depth, but much of the wider Vale of Pickering has organo-mineral’ topsoil with a significant carbon content. (There are generally some big areas of very dark soils). There are also large areas of sands, gravel, silt and clays from glacial ‘Lake Pickering” and outwash fans and so on. Lake Flixton persisted several thousand years longer and well in to the interglacial, which I guess is when climate was warm enough for swampy vegetation to grow in the wetland and form fen peat. Either way, there must be a significant carbon store in the Vale of Pickering floodplain soils.