The rocky precipices have always remained free of peat and many of the hilltops have been laid bare by peat erosion and weathering. As a result the summits and crags resemble parts of the Arctic and lower Alps, being sparsely vegetated with shrubs, mosses and liverworts. The plants include some ‘arctic-alpines’, which were amongst the first species to colonise Glenveagh after the Ice Age. This wilderness supports a meagre and specialised range of wildlife.
Upland blanket bog, which today covers the greater part of Glenveagh, was preceded by forests of Scots pine and birch, giving way to oak, hazel and alder on the lower slopes. Today it is difficult to believe that tree cover extended to the upper slopes, but the evidence of unearthed tree stumps in the bog prove that it did. Remains of the ancient pines can be seen protruding from weathered peat on many hills in the Park.
The blanket bog to be found in Glenveagh is of the western or Atlantic type, which is found only in Ireland, Scotland and Wales. Peat cover is uneven and of varying dampness and bedrock is widely exposed. The result is a mosaic of vegetation types.
The park contains about 100 hectares of natural and semi natural woodland. The largest stretch is Mullangore Wood on the south eastern shore of Lough Veagh, although several remnants are to be found on the steep slopes of Glenveagh where the terrain is too precipitous for blanket bog growth. The woods are amongst the few native stands of timber left in Co. Donegal.
The woods are dominated by oak and birch, with lesser amounts of rowan, holly, hazel, yew and aspen. Woods of this kind are called western Oakwoods and occur principally in the uplands of Ireland, Scotland and Wales.
Lakes in the park range from the small lochans to the long deep waters of Lough Veagh, the main body of water in the park. The areas from which the lakes collect their water all lie entirely within the park boundary, making it possible to prevent their pollution.
The waters are clean and well oxygenated and are particularly suitable for a range of species to thrive.