This book surprised me. The beginning, where Rosenzweig cites a few examples of humans co-existing with their natural landscape to the benefit of both, is folksy and upbeat, and I thought this was going to be yet another lengthy, non-specific entreaty to treat the land gently. And then in Chapter 8, Rosenzweig writes an excellent summary of one of the biggest breakthroughs in ecology, the mathematical relationship between area and number of species. He doesn't stop being folksy (there are more biblical quotes in this book than I believe I've ever seen in a science book), but he nails the problem with conservation biology in preserving biological diversity: with 5% of the earth's territory under reserve, you're not even saving 5% of the earth's species, because there is a logarithmic relationship between area and diversity. If you read climate change books, you're used to seeing the exponential curve, which is runaway change. The logarithmic curve is the opposite shape: a small increase in x-axis leads to large change in y, but the change levels off after a while into a plateau. In optimistic terms, that means you can put a little bit more land into a reserve and get a large increase in diversity. In pessimistic terms, that means that the 5% of the land currently in reserves may only save something like 1% of the biological diversity of the planet, and the numbers may not achieve parity until they get bigger, which seems impossible, given how difficult and expensive it is to manage just that 5%.

This is one of those books which really drives home the enormous gap in scientific literacy between professional scientists and everybody else. Ecologists understand the scope of the human-driven extinction event of which we're in the middle, and how the choices that we've already made are going to affect the next few hundred years, based on mathematical certainties like the species-area relationship. Does anybody else? ( )