Flannery begins his ecological history of North America 65m years ago with the Chicxulub asteroid impact spraying molten rock far into the present Canada and creating a shockwave that flattened trees across the continent. North America lost 80% of its flowering plant species and the dust polluted the atmosphere so most photosynthesis stopped as the planet entered a decade of freezing temperatures.
From here the book describes the major ecological developments through to the present, starting with how the continental drift of Australia from Antarctica and the rise of the Panamanian isthmus impacted on North America's climate. Even when writing of continental drift, Flannery's account is fast-paced. Some will deplore Flannery's speculations, but I found them intensely stimulating. One speculation is not necessarily like another: a well-informed speculation can help to eliminate more far-fetched speculations.
This quote exemplifies his well-informed speculation:
"The lifestyles of the oreodonts have been a mystery for some time. Some possessed eyes on the top of their heads like hippos, which certain researchers have taken to indicate an aquatic life. Oreodont remains, though, are most common in windblown sediments, indicating dry conditions. New and still contentious studies focusing on well-preserved remains of animals that were presumably buried where they lived suggest that some oreodonts may have been burrowers. Some skeletons even have the remains of foetuses, usually, two, three or four, preserved in their mother's belly. Such large animals tend to have so many young only if they live a precarious life, prompting one researcher to suggest that oreodonts used those eyes atop their heads to peek over the rims of their burrows before emerging. But what kind of danger were they keeping an eye out for? The caution of the oreodonts may have been prompted by the pig-like entelodonts...."
Throughout the book Flannery lifts the lid on some of the liveliest scientific controversies. Thus he begins the second half of the book with a clear account of carbon-14 dating and the debate about whether the extinction of most American megafauna was caused by climate change or the arrival of the American Indians. Both debates have political implications for present social policy and Flannery does not, thankfully, smother his account with politically-correct obfuscation.
Chapter 23 describes the destruction of the American Indians - an eye-opener for someone like me who, as a child, played "cowboys and Indians" on the premise that the two sides were evenly matched.
Flannery is fascinated with the notion of "frontier" as was Frederick Jackson Turner who documented the closure of North America's physical frontier; but for Flannery the frontier lives on in US popular culture.
Flannery describes how the myth of the eternally bountiful frontier has fostered a cavalier disregard for environmental laws and other attempts to constrain profligate behaviour. A nation "conceived in liberty" actually had its cultural and political freedom underwritten by rich glacial soils, abundant water and ecological diversity. When these frontier underpinnings no longer apply, US culture will have to adapt to survive.
Flannery leads the reader to ask if the spread of American frontier culture to nations without the bounty of North America has been at huge cost to their environment. Flannery's second theme is his three-phase model of "founder effect", "release" and "adaptation". The founders find an ecological niche and exploit it and in the absence of competition almost all variants make a living of some sort. "Release" occurs when a species is newly arrived in its environment with few competitors and abundant resources; they diversify and flourish in their new conditions. In Flannery's book, the same applies to grizzly bears as to humans on the "eternal frontier"; however, release and adaptation is faster with humans as culture can change more rapidly than biology. When abundance diminishes, species have to adapt to their environment. Because North America is such a rich continent, Europeans have as yet adapted very little - a phase they must enter to produce a diverse and truly North American society. He observes that North Americans still seek frontiers to exploit (irrigating the deserts, even exploiting space - their last frontier) rather than adapting.
This review cannot hope to bring out the richness of Flannery's book. It flows so effortlessly that the reader barely notices the superscript references that follow many paragraphs which show that he has woven together his 365 sources into a seamless tale.
Flannery takes Aldo Leopold's dictum about restoring the environment and shows that there was no complete ecological balance in pre-European or pre-Indian times.
This introduces the question of how the wilderness areas should be managed for the future. Flannery seeks to "revolutionize our rangelands management" by proposing a megafauna to recreate the more balanced ecology of 13,000 years ago: elephant (to replace the mammoth and mastodon), bison, llama, tapir, jaguar, camel and Chacoan peccary - all of which could be harvested for mutual human/megafauna/ecology benefit.
My criticisms of the book are minor and I would not like them to be taken as detracting from this otherwise positive review. The seven-page index is adequate but has not been compiled by someone who understood Flannery's theoretical models. It would have been more helpful, too, if all the animal and plant species mentioned in the text were included in the index. The maps are inadequate: they do not show the majority of the sites mentioned, nor the locations of the Indian tribes referred to. The addition of timelines and illustrations (even silhouettes) of all the animals covered would enrich the book.
Flannery's book has come at an opportune time. Most topically, when the US is considering the implications of the most recent census, when the Bush administration is finding its feet in terms of environmental policy and when creationist escapism is threatening scientific education. More significantly, because the physical and biological frontier, eternal for millions of years, has been closed for all time by the latest mass immigrant and mass exploiter: homo sapiens.