After the last Ice Age, the devastated Cheviot landscape would have been re-established as tundra, with moss and lichen and then sedges and grasses.
Pollen analysis shows evergreens such as pine and juniper had appeared by around 8000 BC, followed by birches and hazels. The major deciduous tree varieties, such as oak and elm, had populated the valleys and the Cheviot slopes by between 6000 BC and 5000 BC, but shortly thereafter numbers of open areas were appeared in the woodland, possibly the result of fires set by Mesolithic hunters hoping to attract animals to the newly grown grass.
Substantial land clearance for farming started in the Neolithic period at around 2500 BC. Cereals are seen in pollen studies and there were increased sediment deposits in waterways downstream, as a result of post-clearance erosion. Clearances continued through the Bronze Age and the Iron Ages, despite the deteriorating climate. Cooler conditions may have encouraged development of farmland to compensate for reduced yields.
Over time, clearance helped create the Cheviot peat bogs. Eroded soil blocked drainage and rainwater accumulated behind the obstruction. As the farmers left, so heathers and rushes moved in; when they died their debris decomposed slowly and peat started to accumulate in the wet ground, resulting in a deep blanket bog.