Amnesia makes variety the spice of death

We live in a world where many of the most exciting animals and ecological communities have disappeared because of humans. Even within a lifetime, it is possible to notice that some bird species or areas of good habitat are less common. Yet, because each generation inherits an apparently diverse and exciting biological world, we are unaware of what has been lost. The Condor's Shadow is an excellent antidote to this "generational amnesia", as David Wilcove calls it.

Wilcove presents an interesting account of how humans have completely changed the ecology of the United States. Today, more than 85 per cent of the virgin forests in the US have been logged, 90 per cent of the prairies have been ploughed or paved, and 98 per cent of the rivers and streams have been dammed, diverted or developed. As a result, Wilcove's book is an apparently endless list of human-caused ecological disasters. The bad news is interspersed with a few accounts of recovery or successful conservation, but any history of human colonisation of a continent is never going to generate much good news.

The book is grouped into chapters according to habitat or geographical area. Each chapter gives brief but accurate accounts of the main historical changes by humans to the habitat. The accounts are biased towards the past century, but this is a consequence of a general lack of any hard data for earlier periods. Earlier changes such as fire regimes and removal of the effects of keystone species such as prairie dogs and beavers are discussed, but in a more speculative manner. Such speculation is clearly presented and enhances the book: much of it is probably correct and puts the changes that are observable today into perspective. The chapters covering the eastern forests concentrate on deforestation and the surprisingly few extinctions that resulted. Western areas are discussed mainly with respect to the management of large animals in Yellowstone National Park and the disastrous consequences of a general fire suppression policy within the Ponderosa pine forest of Arizona. Further chapters deal with the prairies, rivers (much on the loss of the US's incredible diversity of freshwater mussels), coastal wetlands, and the sub-tropical areas of Florida (mainly the Everglades) and Texas. The final chapter deals with Hawaii and the incredible devastation that has occurred there. A visitor to the islands may see lush forested hillsides and diverse communities of animal and plant species, but they consist almost entirely of introduced species. Hundreds of species that occurred uniquely in Hawaii have disappeared since humans colonised the islands, and the few that remain are disappearing by the year.

A large fraction of the book is notes and references, sensibly organised so that the reader can take the book either as an overview, or as the starting point to explore the complex ecological problems introduced by the author.

This is perhaps the real success of the book. It can be read by people at all levels of interest and understanding. For university ecologists Wilcove explains the relationships between well-known ecological problems that are frequently studied in isolation. For general readers, even those without an interest in conservation, he provides a fascinating historical account of how humans have affected every aspect of the environment.

As a European, I am used to disturbed landscapes, and prior to reading Wilcove's book, I viewed much of the landscape in the US as comparatively pristine. Individual accounts of conservation problems in North America had not really given me the impression of the totality of the problem of anthropogenic changes there. The strength of The Condor's Shadow is that it gives the overview necessary to appreciate this. It is a good read as well, if a bit depressing. But, as Wilcove says: "Only when we take the time to assemble the bits and pieces of information from past generations and present them in an ordered way can the cycles of change, the losses and gains, in our wildlife population be appreciated. And only then are we likely to cherish those species and wildlands that might otherwise pass unnoticed from this country and this world".

Will Cresswell is lecturer in ornithology, University of Oxford.