The twentieth century brought about sweeping environmental, economic, social, and political change. Each type of change was itself substantial, but collectively these changes collaborated to produce unprecedented impacts on the Earth and the human way of life. In this lecture, Nay Htun, Deputy Director of the United Nations Environmental Programme, addresses these changes and places them in the context of global environmental change. Dr. Htun describes the forces negatively affecting the global environment and talks about possible solutions to these impacts.