The Caledonian Forest is the ancient (old-growth) temperate forest of Scotland. The forest today is a reduced-extent version of the pre-human-settlement forest, existing in several dozen remnant areas. The Scots pines of the Caledonian Forest are directly descended from the first pines to arrive in Scotland following the Late Glacial; arriving about 7000 BC. The forest reached its maximum extent about 5000 BC, after which the Scottish climate became wetter and windier. This changed climate reduced the extent of the forest significantly by 2000 BC. From that date, human actions (including the grazing effects of sheep and deer) reduced it to its current extent. Today, that forest exists as 35 remnants, as authenticated by Steven & Carlisle (1959) (or 84 remnants, including later subjective subdivisions of the 35) covering about or . The Scots pines of these remnants are, by definition, directly descended from the first pines to arrive in Scotland following the ice age. These remnants have adapted genetically to different Scottish environments, and as such, are globally unique; their ecological characteristics form an unbroken, 9000-year chain of natural evolution with a distinct variety of soils, vegetation, and animals. To a great extent the remnants survived on land that was either too steep, too rocky, or too remote to be agriculturally useful. The largest remnants are in Strathspey and Strath Dee on highly acidic, freely drained glacial deposits that are of little value for cultivation and domestic stock. An examination of the earliest maps of Scotland suggests that the extent of the Caledonian Forest remnants has changed little since 1600. History Following the last glacial period, trees began to recolonise what is now the British Isles over a land bridge which is now beneath the Strait of Dover. Forests of this type were found all over what is now the island of Great Britain for a few thousand years, before the climate began to slowly warm in the Atlantic period, and the temperate coniferous forests began retreating north into the Scottish Highlands, the last remaining climatic region suitable for them in the British Isles (see Climate of Scotland). The native pinewoods that formed this westernmost outpost of the taiga of post-glacial Europe are estimated to have covered as a vast wilderness of Scots pine, birch, rowan, aspen, juniper, oak and a few other hardy species. On the west coast, oak and birch predominated in a temperate rainforest ecosystem rich