Monday, February 14, 2011

Human Impact: Riches from the Earth

              The Earth is minded for building materials, metals, chemicals and fuels. Powerful machinery, industrial processing and international trade mean that individual deposits are exploited on a scale far beyond local needs. An estimated 23 billion tones of non fuel minerals are extracted each year, about twice the amount of sediment carried each year by the world’s river systems. As a result, an estimated half a million hectares of land are scarred each year. As the most concentrated ore deposits become exhausted, lower grade ores are used, such that to produce an estimated nice million tons of copper in 1990, 990 million tons of ore had to be mined. The open cast Bingham Canyon copper mine in Utah, USA, 775m deep, is the largest human excavation in the world.

      The legacy of mining is not only the hole in the ground and the pile of spoil left behind; it can affect air and water over great distances. The Ilo smelter in Peru emits 600000 tons of Sulphur compounds each year, and cyanide in the waste affects marine life in a 20,000 hectares area. Small scale gold mining by hundreds of thousands of miners in the Amazon basin releases a estimated 100 tones of mercury into the river system each year.