Large environmental changes are occurring all around us. As the human population has grown, the demand for food, energy, water, living space, and amenities has also grown, as has the production of industrial wastes, sewage, agricultural run-off, and carbon dioxide – the monster of all waste products. These changes are not always obvious to the naked eye, and the lack of a clear understanding is often a major barrier to taking appropriate action. This is where the environmental scientist is needed: to shed light on the what, where, when, why, and how of environmental change.