This lecture recounts personal experiences and discusses environmental issues that invoked a desire to teach about the things threatening the earth. Human population growth is cited as the first and foremost environmental challenge in the 20th century. A J-shaped curve is used to illustrate an increase in human population. The relationship between population growth, the human appetite to consume the earth's resources and the intensification of pollution problems is cited. Other related problems include water resource feuds, energy source depletion, contamination, greenhouse effect, and climatic changes. These problems are explained and illustrated with specific incidents of environmental conflicts. Oil resources are referred to as one of the most important issues of the next decade because of its close tie with the economic well being of the United States. The use of non-polluting renewable energy sources and further study are encouraged to allow for a better understanding of our relationship to the natural world and to foster sustainable systems. (Contains 14 references.) (MCO)