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At the height of the last glaciation (100,000 - 12,000 BC), most of Britain would have been bare of trees. Birch and willow scrub possibly persisted along the lower margins of the ice, with pine in places. Relicts of pre-glacial flora may have survived in sheltered bays along the western coasts of Great Britain and Ireland, but elsewhere as far as the south of England, ice swept the land clean. The development of Britain's post-glacial flora can be deduced from studies of pollen and seed deposits in peat, and by means of radiocarbon dating. Tundra and moorland followed the retreating ice, and then waves of colonisation by different tree species spread from the south. The first were birch, aspen and sallow, and then about 8500 BC pine and hazel spread north, replacing birch which became uncommon for several thousand years. Oak and alder followed the pine, then lime, elm, holly, ash, beech, hornbeam and maple in succession spread northwards. The earliest trees were those of arctic conditions; the later trees were those of warmer climates. The earliest trees spread the furthest north, with alder reaching Ireland shortly before it was cut off as sea levels rose. The later species were slower to move north and to become abundant, as there was no vacant ground to colonise. Beech and lime did not spread beyond southern Britain. From the time lime arrived, in about 7300, to about 4500 BC there was a period of relative climatic stability called the Atlantic Period, during which the various species settled to form a series of wildwood or wilderness types, as shown in the diagram. The tree line was much higher than now, as shown by the remains of trees found in present-day moorland. The tree line varied across the country. The far north of Scotland was treeless to sea level, but in the eastern Highlands may have been as high as 915m (3,000ft). In the North York Moors tree remains have been found at 360m (1150ft), but parts of Dartmoor at 610m (2,000ft) have apparently always been treeless. The only natural grassland was probably small areas on high mountains, or on exposed maritime cliffs.
What did the wilderness or wildwood look like, before man starting interfering with it? A recent theory is that the wilderness in Western Europe was a mosaic of grassland, scrub, individual trees and groups or groves of trees (Vera, F.W.M, 2000). It was not a closed, impenetrable wildwood, but was a park-like landscape, maintained by the grazing and browsing of wild herbivores. This may have been true in Britain during earlier interglacials, when the great beasts of the Palaeolithic era required large areas of grassland. Pollen records show that a wide range of grassland plants persisted in the last interglacial. However, since the last glaciation, the bison, elk and other large herbivores which persisted on mainland Europe were extinct in Britain, so Vera's theory may not apply so well to Britain. However, the persistence of oak in Britain throughout the period since its spread northwards after the last glaciation may be an indication that the wildwood was not continuous. Oak is a pioneer species, which requires open ground in which to regenerate (see flora and fauna). It requires grazing animals to maintain open areas, and regenerates in the thorny scrub which protects it from browsing. Archaeological evidence shows that red deer, which are grazers of grass as well as browsers of trees, were a mainstay of the Mesolithic economy in Britain, being used for their meat, skins, antlers and bones. Aurochs or wild cattle, which were present in Britain until the Bronze Age, were specialised grass eaters, and required grassland not closed forest. All content copyright © 1986-2008 BTCV Ltd. Registered charity No. 261009 |
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