Welcome to the second edition of the Gale Environmental Encyclopaedia! Almost everything in the world has some environmental significance, be it physical, chemical or the biological world that surrounds us. This giant encyclopaedia not only covers this natural world, but also the 'built' or technological environment as well as the cultural and social context that shapes human lives. Showing central concerns on environment science, it brings out questions like: How did the natural world come to be as it is? How does it work? It attempts to answer them from a variety of different perspective. The articles and definitions given depicts the importance of understanding our environment and our relation to it.