Woodland is a scarce yet important component of the Yorkshire Dales landscape. Semi-natural ancient woodlands dominated by self-sown native species are the most important types of woodland in the Dales for biodiversity conservation. These include upland mixed ashwoods, upland oakwoods and wet woodland.
Upland mixed ashwoods are found on base-rich soils in the north and west of upland Britain. Ash woodland is the most abundant and widespread type of woodland in the National Park. The canopy is comprised of ash, wych elm , sycamore with an understorey of downy birch, rowan, bird cherry, hawthorn and holly. The composition of the ground flora depends on the level of grazing and canopy cover but is usually dominated by dog's mercury, bluebell and wood avens with wild garlic in the wetter areas. Ferns such as male fern and lady fern are also abundant. Good examples can be seen at Grass Wood in Wharfedale, Freeholders Wood in Wensleydale and parts of the Ingleton Waterfalls trail.
Upland oakwoods are rare in the Yorkshire Dales National Park. Many of them have ground flora and shrub layers typical of oakwoods but oak trees are no longer present due to felling, however good examples of remnant oakwoods can be seen in parts of the Bolton Abbey Estate and parts of the Ingleton Waterfalls trail.
Wet woodland occurs on poorly drained or seasonally wet soils, usually with alder, birch and willow as the predominant tree species. Wet woods frequently occur as mosaics with other woodland types and with open habitats such as fens. Good examples of wet woodland In the Yorkshire Dales National Park include around Malham Tarn and around Semerwater.
Woodland has been cleared for a variety of purposes since the last Ice Age resulting in the current low cover in the Dales. Semi-natural woodlands are now very scarce in the National Park and account for only 1 % of the Dales area. Many of these are very small in size and have been modified for many centuries through clearance, heavy stock grazing or re-planting with non-native species. Consequently native woodland continues to be one of the National Park priority habitats and the subject of active work by a number of organisations.