It is still too early to predict exactly what will happen, but we can speculate on the effects a different climate will have on the landscape of the National Park.
If the summers are longer, hotter and drier, the blanket bogs across the uplands will begin to dry. There will likely be more grass and heath fires, changing the patterns of vegetation across the uplands and encouraging more bracken. As river levels drop some species (such as those that favour the fast flowing upland streams) may disappear or fish such as salmon and trout may find difficulty spawning. Some trees such as beech may be effected by drought stress and a few bad years could soon kill them off.
Mild winters may mean some seeds no longer germinate as they require frost or lower temperatures to trigger their development. Migratory birds may stay longer and longer putting more pressure on what food is available. Mild temperatures will also lead to more mammals, birds and insects surviving the winter, meaning a sharp increase in their populations. While this may seem good news in the short term, these increased populations can cause problems as they compete with other species and themselves for food and nest sites.
Heavy rains, particularly after summer droughts could cause flooding and erosion of soils. The extra sediment washed into rivers changes the water chemistry affecting every freshwater plant and animal, while the settling of the sediment can bury gravel and stone river beds with mud, depriving some species of the conditions they need.