The plantation movement did little to offset Britain’s growing reliance on overseas supplies, or the decline in management of traditional woods. By the beginning of the 20th century about 90% of all timber and forest products were imported. The bulk of this trade was softwoods from Scandinavia and North America, with tropical hardwoods also important. The strategic danger of this situation became obvious in the First World War (1914-1918), when enemy action prevented imports getting through. Over the four years, about 180,000 hectares (450,000 acres) were felled to meet the demands.
The establishment of the Forestry Commission in 1919 aimed to ensure that the near disastrous shortage of wartime timber would never occur again. By 1939 the Commission had established 230 forests on about 265,000 hectares (655,000 acres) of land, with 145,000 hectares (359,000 acres) actually planted up. These forests were of fast-growing timber, mainly conifers, planted close together to get the maximum amount of timber per acre. Large even-aged blocks of single species or simple mixtures of straight line planting were often thrown across the landscape with little regard for variations in terrain or local features.
By the time of the Second World War (1939-1945), the Commission forests were still too young to provide much timber, and about 212,000 hectares (524,000 acres) of private woodland were felled to meet the demand.
However, felled woods, left to their own devices, regrow. Much more damaging to the remaining semi-natural woodlands of Britain were the agricultural and forestry policies which were followed after World War II. Rackham (1990) estimates that nearly half of the remaining ancient woodlands of England, Wales and Scotland were seriously damaged or destroyed in the period 1945-75. In that 30 years there was more damage and destruction than in the previous 1000 years. The biggest losses were to agriculture and to forestry, with housing, roads and industry using only small amounts. After the food shortages of World War II there was a perceived need to maximise food production by bulldozing woodlands and hedgerows, destroying them so they could not regrow. Agricultural grants were directed at the clearance of woodlands and hedgerows in order to maximise production. At the same time, improved varieties of agricultural crops were increasing yields to such an extent that these clearances were in fact unnecessary. Many semi-natural woodlands were cut down and replanted with conifers, for timber production. The damage here has turned out to be less severe than might be expected. In many woods the planted conifers failed to thrive, and the deciduous species grew back and are now once more dominating these woodlands.
During the last decade of the 20th century there was a great change in Forestry Commission policy. The UK commitment to biodiversity following the Rio Earth Summit (1992) has resulted in Biodiversity Action Plans being drawn up by government conservation and forestry agencies and other organisations, which include commitments to conserve and extend semi-natural woodland. The publication by the Forestry Commission of their Practice Guides The Management of Semi-Natural Woodlands (1994) signalled the great change in policy and practice. The importance of using local provenance planting stock is now accepted. Grants are given towards encouraging natural regeneration. Ancient woodlands which were planted with conifers are now categorised as Plantations on Ancient Woodland Sites, and advice is directed at their restoration. Management and felling of the maturing plantations continues, but the way forward is by managing woodlands through continuous cover systems, coppicing, and other systems which maintain traditional woodland cover. The importance of veteran trees is now recognised.
Grants are directed at tree and hedgerow planting and management, creation of ponds and other habitats, in a direct reversal of the post-war policies. Those who have farmed throughout this period have been given grants to clear and destroy, and then grants to plant, create and restore.