Ben Zuckerman discusses the impact of a growing US population on the natural environment. According to Zuckerman, overpopulation is clearly an intergenerational and interspecies ethical issue. California's diversity hot spots are closely related to California's areas of high population growth. Zuckerman describes how California is more densely populated than Germany and by 2040, California at 50 million, will surpass China's population density. More importantly, Zuckerman emphasizes that unlike China, California has no plan to fix its population crisis. Zuckerman points out that our current economic model requires high per capita consumption, which is in direct conflict with the requirements of sustainability. Because of the impact of population growth on our environment, catastrophic events, rather than the decisions of rational human beings, are likely to determine the course of events over the next century.