Flannery opens with a vivid account of the great catastrophe signalling the extinction of the dinosaurs. The wandering rockball that slammed into the remnants of the Bearpaw Sea 65 million years ago reset the evolutionary clock. Because of its position above the target site, North America became a hotbed of evolutionary diversity after the collision. A setting dominated by North-South running mountain ranges [where East-West is the usual pattern elsewhere] gave rise to severe changes in weather, with resulting adjustments of life forms. Megafauna, the giant animals that ultimately dominated the landscape, ranged across the prairies. They included the uintatheres – triple-horned giants, the first camels, horses and sheep-sized animals whose herds covered the land. Flannery shares his awe of life’s diversity on this continent during the period of recovery after the asteroid’s devastation.

Flannery depicts a wedge-shaped North America as a trumpet” with the capacity to amplify weather conditions. When climate conditions changed slightly elsewhere, they were embellished here. The result was seen in both flora and fauna as plants and their herbivore predators adjusted. Conditions finally combined to produce the masses of ice that penetrated deeply south. Flannery tracks the gateways into North America left by the erratic ice [he also concedes that Canada's fossil record was nearly scraped away by the frozen cliffs]. The most significant creature to find a path from elsewhere, of course, proved to be “the hunting ape.”

The entry of humanity to this nearly unique stage brought truly immense change. Flannery recounts the disappearance of many species of animals, nearly all of them the remnants of the earlier megafauna. No other predator, and not climate, he contends, could have exterminated so many animals so quickly. Only humans, with their organization and weapons could have devastated the megafauna. He shows how the same time frames have parallels in Australia and the Pacific. The bison survived the initial invasion due to their large herd size and mobility.

The European wave of human invasion was the most devastating. These new immigrants brought something new in their baggage – technology. New forms of manufacture and transportation overwhelmed the North American scene, transforming drastically. Farming changed from small plots to vast acreages. These installations required mechanical devices for tilling and harvesting. More importantly, they demanded water. In the West, where farming was at best a marginal enterprise, Flannery relates the environmental stress dam building caused. New manufacturing and transportation systems required minerals, which were to be found in the Basin and Range. Mining, damming, ranching intruded on the natural environmental patterns yet became the basis for what is termed “the American System.” For Flannery, this frontier economy remains entrenched as the foundation of American thinking. “Globalization” is nothing more than the extension of the “System” expanded to remainder of the world irrespective of its relevance elsewhere.

Flannery, however, doesn’t view the disruption as irreversible. He urges a full understanding of pre-human invasion conditions as a basis for restorative action. He doesn’t believe in setting aside “wilderness areas” as a conservation measure. His prescription is a pro-active approach – the re-introduction of large herbivores to recover lost ecologies. African and Indian elephants introduced to the western prairies, for example, would aid in restoring depleted grasslands. He examines other indicators that suggest North Americans can stop the resource-depleting juggernaut, each of which the reader must consider carefully and with and open mind.

There are few flaws in this book. The indexer needs to enter a study program with a good thesaurus, and the money spent on glossy colour photographs might better have gone to more line diagrams. These are petty considerations next to the book’s important message. Every student in North America should be given a copy of this book. It is, after all, their future Flannery is addressing.