SOME OF Britain’s oldest roads are being endangered by environmental change caused by rural development, a study in the Somerset Levels has found. Two late prehistoric wooden trackways, both scheduled ancient monuments, have been completely lost because of the drying out of prehistoric wetlands by arable farming. A unique Iron Age wetland settlement of about 400 BC has also been badly damaged, along with nine other nationally important waterlogged archaeological sites.

The study has shown that other fragile archaeological sites could be all but destroyed by agricultural drainage within a century. The threat to these sites is in the summer, when the ground-water table drops below the level of the waterlogged remains, drying them out. Current farming practices are not providing sufficient irrigation of peat soil to preserve the monuments. While the Sweet Track, dated at about 3800 BC, is within the Shapwick Heath National Nature Reserve where a purpose-built pumping system protects it from desiccation, it is an isolated instance of a protected site.

The focus was on 13 of the most important sites on the Somerset peat moors near Glastonbury, including prehistoric trackways, villages and other monuments. It showed that some sites had already been lost while others were suffering gradual decay.

Drainage in the Somerset Levels probably began several centuries ago, when the wetlands were first enclosed, but has accelerated in the past 60 years as farmers have employed more efficient pumps.

Vanessa Straker of English Heritage said: “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.”