The more people there are on the planet, the more we push aside wild plants and animals. This text explores the cause-and-effect relationship between these two trends, demonstrating that nature is too sparing to accomodate both a diverse living world and a rapidly expanding number of people.

Because it is clear that conservation cannot be left to the whims of changing human priorities, McKee takes the unabashedly neo-Malthusian position that the most effective measure to save earth's biodiversity is to slow the growth of human populations. By conscientiously becoming more responsible about our reproductive habits and our impact on other living beings, we can ensure that nature's services will make our lives not only supportable, but also sustainable for this century and beyond.