The Tireragan landscape is determined by a number of factors and these are primarily climate, geology and human habitation, the latter whose effects have been felt for at least six thousand years.
The weather is dominated by the Atlantic Ocean with very little to stop a stream of oceanic lows racing across thousands of miles of open water. The rain that such systems inevitably bring result in the formation, most obviously, of peat bog but also effect all other habitats including the woodlands. The damp conditions give rise to a temperate rain forest where mosses, lichen and liverworts cover the trees.
Another climatological present the Atlantic bestows upon Tireragan is wind, lots of wind. The prevailing westerly winds blast the exposed coast and higher grounds making growth for large plants very difficult if not impossible. The oceanic climate also means even and relatively warm temperatures year round.
The underlying geology consists mainly of the famous Ross of Mull pink granite with some small outcrops of moine schist. The soils formed from granite are fairly poor so that, together with the effects of wet and windy weather, there is little good ground for growing crops. However these poor soils are a major factor resulting in the habitats that make Tireragan so special.
When Highland Renewal took over management of the estate in 1994 the first priority was to remove the sheep and deer and erect a fence to keep them out. Over the previous 150 years or so, land management practises to promote grazing for the sheep including regular burning of the moorland, effectively preventing the natural succession of the vegetation. Unfortunately, these burning practises also significantly increased the degree of erosion, resulting in more of the underlying rock being exposed.