For the past 3.8 billion years, the geochemistry of the Earth's surface - its atmosphere, waters and exposed crust - has been determined by the presence of biota. Photosynthetic organisms exposed the Earth's surface to oxygen, denitrifying bacteria have maintained the nitrogen concentration in Earth's atmosphere, and land plants have determined the rate of chemical weathering. Life determines the global biogeochemical cycles of the elements of biochemistry, especially C, N, P and S. Volume 8 traces the origin and impact of life on the geochemistry of the Earth's surface, with special emphasis on the current human impact on global biogeochemical cycles. Reprinted individual volume from the acclaimed Treatise on Geochemistry, (10 Volume Set, ISBN 0-08-043751-6, published in 2003)