Once the ice sheets had melted and the climate began to warm, the landscape of the Yorkshire Dales gradually changed from open tundra to dense woodland. By around 8000 BC, pine and birch dominated the woodland cover. These were slowly replaced by lime, elm and oak with some hazel. By 6500 BC, pine and birch woodland would only have been found on the thinner limestone soils of the Craven uplands. The large herds of reindeer and horses found on the open tundra were replaced by harder to find woodland creatures such as red and roe deer, auroch (wild cattle), wild pig and elk.
With up to 90% of the land covered in woodland of one sort or another, the hunter-gatherers of the Mesolithic needed all the open ground they could find to hunt larger animals like deer using their flint tipped bows and arrows. The land around upland natural water sources such as Malham Tarn and Semerwater was ideal. Limestone country is always short of open water and being at or just above the tree line meant that herds of red deer and wild oxen would naturally gather to graze and water in the summer months. The lakes also provided plenty of smaller game such as birds and fish.
We know that the hunters were here because archaeologists have collected thousands of their flint artefacts from sites around both lakes. Recent field work and excavation by Bradford University around Malham Tarn has thrown more light on the people who used it as a hunting base. It seems that in the later Mesolithic, people were camping out on areas of slightly raised ground close to the shore of the Tarn. Geophysical survey work has shown that at one of these camp sites, there are several possible hearths.
Charcoal has also been found in Mesolithic contexts in the wetlands above the Tarn. It seems likely that the hunters burned back the edge of the woodland in order to create more open ground for their prey to graze on. This would also have favoured the growth of hazel, since unlike other woodland trees, hazel grows back easily from a burnt stump. With hazelnuts being a very important winter food source at this time, the hunter-gatherers may have had this aim in mind too. People had begun to alter their environment and it was the beginning of the end for the wild wood in the Yorkshire Dales.
Recent survey work on Little Asby Common in the Westmorland Dales using augurs to take deep soil samples has also produced microcharcoal particles suggesting wood clearance by fire during the Mesolithic period.
The evidence shows that none of the sites around Malham Tarn were ever lived in the whole time. They are much more likely to have been specialised summer hunting camps, particularly the site excavated in Chapel Cave where so many flint microliths were found. This site dates to the early Mesolithic, but nearby sites from the later Mesolithic were also probably just temporary, even if people returned to them on a seasonal basis, year after year. It seems likely that for the rest of the year, the hunters returned to home camps in eastern Yorkshire where a much greater variety of activities took place. There may even have been winter camps on the east coast where food could be had from the sea and sea shore whatever the weather.