areas, and selling it off in plots, persuading buyers that the government will have to weaken Green Belt protection to solve the housing crisis (see below). It is hard to see when such plots could come back into production. Fossil fuels The UK's industry sector was once dominated by the coal; heavily concentrated in south Wales, north and south Staffordshire, Leicestershire and Derbyshire, South Yorkshire, Northumberland, County Durham, Fife and Midlothian. The number of pits and miners have been slashed, and output fell by more than 75% between 1981 and 2003. The remaining pits produced 17.2 million tonnes of oil equivalent in 2003, making the UK the 15th largest coal producing nation, compared with 4th in 1981, according to the BP Statistical Review of World Energy 2004. The major primary industry is North Sea oil. Its activity is concentrated on the east coast in Scotland and Northern England. The waters in the North Sea off the east coast of Scotland contain nearly half of the UK's remaining oil reserves, and a quarter of reserves are located in the North Sea near the Shetland Islands. As of January 2004, the UK had proven crude oil reserves of 4.7 billion barrels (750,000,000 m³) including onshore reserves, according to the Oil and Gas Journal. A closely related industry is natural gas which, since the 1970s, has supplied all of the UK gas needs, replacing poisonous coal, or town, gas. Most natural gas production is in the North Sea, with a small amount onshore and in the Irish Sea. The largest reserves not related to oil production are in the southern North Sea between the UK and the Netherlands, although; the largest reserves, are associated with oil production. The UK is expected to become a net natural gas importer before 2010. Manufacturing At one time or another virtually every product that can be imagined has been made in the UK. In particular its heavy manufacturing drove the industrial revolution, starting with the first blast furnace at Coalbrookdale in Shropshire. A map of the major UK cities gives a good picture of where manufacturing flourished, and often specialisations could be identified, in particular: Birmingham (automotive) Glasgow (shipbuilding) London (various) Manchester (textiles) Bradford (textiles) Newcastle (shipbuilding and steel) Nottingham (apparel, medicine) Stoke-on-Trent (ceramics) Sheffield (steel and steel products) Leeds (textiles and engineering) Belfast (shipbuilding and textiles) Cardiff (steel) The automotive industry can be traced back to