Fragile Peatland Archaeology In Peril

Two late prehistoric wooden trackways, which are both scheduled monuments, have been completely lost because of the drying up of prehistoric wetland archaeology by arable farming. A unique Iron Age wetland settlement (c. 400 BC) has also been badly damaged along with nine other nationally important waterlogged archaeological sites.

A new study funded by English Heritage, the Environment Agency and Somerset County Council Heritage Service has examined the condition of 13 waterlogged archaeological sites on the Somerset moors. The threat to these sites is that in the summer, the ground water table drops below the waterlogged remains, drying them out. Current farming practices are not providing sufficient irrigation of peat soil to preserve the monuments.

Excavation of an area of the Iron Age lake village near Glastonbury The study has shown that other fragile archaeological sites, some of which are more than 5000 years old, could be all but destroyed by agricultural drainage within a century. English Heritage is calling for farmers to join Defra's Environmental Stewardship Scheme which would reward them for preserving these monuments through maintaining raised water levels and converting arable land to pasture.

The focus of the study was on 13 of the most important sites on the Somerset moors including prehistoric trackways, swamp villages and other monuments. It showed that some sites had already been lost while others were suffering gradual decay. For example, two Neolithic trackways, The Abbot's Way and Bell Track, 3000-2500 BC, were only 40cm from the present ground surface and were always above the water level throughout a 12 month period of monitoring, making it surprising that any archaeology survived at all. At three sites, including a late Bronze Age structure possibly used for rituals, the water table dipped below the wooden remains for between three and five months during the summer.

Street Piles - Remains of 8th century AD timbers from a causeway that crossed the valley between Street and Glastonbury. The tops of the piles have suffered badly from desiccation, that has caused them to discolour, shrivel up and wither away. The lower parts are still well preserved because they were still waterlogged. Wetland archaeology is particularly important because waterlogging excludes oxygen and prevents the normal aerobic process of decay, preserving wood and other organic materials. This means these sites provide us with a more complete picture of human activity and much fuller understanding of our past than is possible from dry land sites. In addition to artefacts and built structures, delicate insect, seed and pollen remains help us to reconstruct the environmental setting of the sites.

The drainage process of the Somerset moors probably first began several hundred years ago, when the wetlands were first enclosed, and has accelerated in the last 60 years as the pressures of modern farming have led to the advent of more efficient pumps. Archaeologists fear that the destruction will be compounded by climate change, which is expected to lead to wetter winters but drier summers which will threaten the sites when they are most at risk. Experts estimate that peat soil is being lowered by 1-2 cm every year in arable fields and in pastures by 50-75cm every century. This means that the surface of the land is literally sinking by this measure each year as the water dries up.

Richard Brunning, of Somerset County Council Heritage Service said: "Recent studies proved that there was a potential threat to the waterlogged remains, but it was a shock to see the damage that desiccation has caused. The partnership of the County Council, English Heritage and the Environment Agency needs to act quickly with Defra and landowners if we are going to save these sites that give our most complete picture of the past and are so important to Somerset's heritage, as every year more information is being lost."

Vanessa Straker, English Heritage South West Regional Science Advisor commented: "We funded this study because we believe it is vital that we understand the extent and severity of the threat to England 's internationally-significant wetland archaeology. To help farmers understand the heritage on their Main Trench - The 4,500 year old remains of the Abbots Way trackway. The wood is shrivelled and decaying due to desiccation, which is also causing the surrounding peat to shrink and crack up land, English Heritage has produced a free series of leaflets called Caring for heritage on your farm. We are encouraging as many farmers as possible to apply for Defra's Environmental Stewardship Scheme which gives them payments in return for conserving the countryside. "

Partnership working between landowners, English Heritage, the Environment Agency, Somerset County Council, Internal Drainage Boards and other local authorities is also an important way to protect the landscape, as demonstrated by the Sweet Track in Somerset . Part of the site, which dates to around 3800 BC, falls within the Shapwick Heath National Nature Reserve, and here a purpose built pumping system operated by English Nature protects it from desiccation.