Readers can judge for themselves whether the predictions, inescapably uncertain and spatially undetailed, can be valid bases for public actions. The way human technology is driving environmental changes is well revealed. Some of the standard problems are assessed, e.g., the ozone hole, the greenhouse effect, and acid rain. Somerville's writing style is engaging. Non-scientists will be comfortable reading this book.
People often tend to separate the world into living and non-living components.
But when time is included, no such separation makes sense. Carbon, nitrogen, sulfur, phosphorus, and other elements might come to rest in living organisms, then be expelled as waste products from metabolism or decomposed residues after death. Global processes constantly cycle matter and energy between the inanimate and animate worlds. The biosphere thus becomes a major shaper of the global environment. Humans have stretched the impact of the biosphere in several ways.