ABSTRACT
The Warning relies on knowledge from the sciences of natural systems to paint its picture of the environmental degradation that will occur if present trends—all driven by human activity—continue. In December 1992, the Union of Concerned Scientists released a Scientists' Warning to Humanity, signed by the majority of Nobel Prize winners in the sciences, who agreed that human activities are putting us on what they called "a collision course" with the natural world. Scientific research is needed regarding human-environment relationships now more than ever, because the possible damage to the environment is catastrophic and because we have made national and international commitments to changing human behavior; reducing emissions of greenhouse gases and ozone-depleting chemicals, limiting destruction of habitats and ecosystems, and the like. Standard environmental science addresses the functioning of what have been called "environmental systems"—systems such as the atmosphere, geosphere, and biosphere.
