At the end of the nineteenth century it was realised that during the Holocene (‘wholly recent’ life) there had been a series of changes in vegetation. It was thought that the remains of different plants should correspond with species immigration following the last glaciation, and that the sequence of these plant remains reflected past climatic changes. The epoch has five stages: Preboreal (9700-8200 BC), Boreal (Boreas; 8200-6300 BC), Atlantic (6300-3800 BC), Subboreal (3800-600 BC) and Subatlantic (600-00-present).
The start of the Holocene is marked by rapid increase in temperature. During the Preboreal (birch) and Boreal (hazel, pine), the ice sheets and glaciers shrank, and the midlatitudes and tropics received hugely increased rainfall. As lakes and rivers rose, moist grasslands invaded the Sahara and other regions of the world.
The Atlantic Stage (oak) was warmer than today in northern lands. Vegetation spread worldwide except up to the highest mountaintops. Forest ousted much of the northern tundra. The Subboreal (oak) brought cooler drier winters to the midlatitudes. Steppe and prairie plants and animals multiplied. The Subatlantic (grasses, beech, pine) began the climatically fluctuating stage that we live in now.
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