Humans use 50 percent of the world’s freshwater supply and consume 42 percent of its plant growth. We are liquidating animals and plants one hundred times faster than the natural rate of extinction. Such numbers should make it clear that our impact on the planet has been, and continues to be, extreme and detrimental. Yet even after decades of awareness of our environmental peril, there remains passionate disagreement over what the problems are and how they should be remedied.

Much of the impasse stems from the fact that the problems are difficult to quantify. How do we assess the impact of habitat loss on various species, when we haven’t even counted them all? And just what factors go into that 42 percent of biomass we are hungrily consuming? It is only through an understanding of the numbers that we will be able to break that impasse and come to agreement on which environmental issues are most critical and how they might best be addressed.

Working on the front lines of conservation biology, Stuart Pimm is one of the pioneers whose work has put the “science” in environmental science. In this book, he appoints himself “investment banker of the global, biological accounts,” checking the environmental statistics gathered by tireless scientists in work that is always painstaking and often heartbreaking. With wit, passion, and candor, he reveals the importance of understanding where these numbers come from and what they mean. To do so, he takes the reader on a globe-circling tour of our beautiful, but weary, planet from the volcanic mountains and rainforests of Hawai’i to the boreal forests of Siberia.

At times, the view looks rather grim. Yet Pimm, ever the optimist, presents a world filled with mysterious beauty, the infinite variety of nature, and an urgent hope that through an understanding of our planet’s environmental past and present, we will be inspired to save it from future extinction.