Former Distribution of Forest 65 



Ireland, with their very large proportional areas of uncul- 

 tivated land and very small areas of forest, have a much 

 greater proportion of unreclaimed mountain and moor than 

 any country, save Norway, in north-western Europe. 



The uncultivated land bearing natural or semi-natural 

 plant-communities certainly does not, except 



°™®y in certain cases, bear exactly the same vege- 



extension ^ ^. ■, ^■-^ ^ ,■ -, ■-, 



of forest. tation as it did before man began, with 



increasing civilisation, to modify it on a 

 large scale. There is no doubt that by far the greater 

 part of the British Isles was originally covered with 

 forest : in England the whole of the east, south and mid- 

 lands, except perhaps some of the chalk downs and 

 some of the poorer sands, and of the north and west 

 probably everything but the summits of the higher hiUs ' ; 



' There is still considerable difference of opinion as to the normal alti- 

 tude formerly reached by woodland in the British Isles. So far north as the 

 Central Highlands of Scotland thin \vood of Pinus sylvestris still occurs 

 in places up to 2000 feet (c. 600 m.) and even higher. There is evidence 

 from the remains preserved in the peat that woodland once existed in 

 many places at such levels. Thus Lewis has described a bed containing 

 Alnus rotundifolia and Viburnum Opulus at a height of over 2000 feet in 

 the Northern Pennines (see p. 269) and a forest bed of Pinus sylvestris in 

 the counties of Banff andlnverness at a similar height {Scottish Geogr. Mug. 

 1906, p. 249). He attributes the disappearance of woodland in the latter 

 case (as in many others throughout Scotland) to a change of climate — 

 the reappearance of glaciation after an iuterglacial period — but this 

 interpretation is not universally accepted. The altitude to which wood- 

 land extends depends of course not only on the general chmate, but also 

 on the total height of the mountain mass on which it is developed. 

 Thus we should expect a higher altitude to be reached by woodland in 

 the Highlands of Central Scotland, a compact massif with several 

 summits exceeding 4000 feet (1220 m.), than on the narrower and lower 

 ranges of the Pennines, and this is actually the case with the woods 

 existing at the present time. Varying conditions of exposure also play 

 a part in determining the local height to which woodland attains. It 

 is certain that the upper limit of existing woodland has been consider- 

 ably depressed, as in many European countries, during the historical 

 period, largely no doubt by the irowsing of animals pastured in the zone 

 lying immediately above the forest. 



T. 5 



