Few people would deny that human activities are now having a huge impact on life on Earth. Tropical forests are being cleared today, just as temperate forests were cleared 100 and more years ago. The face of the land is changing, and many species of both plant and animal life are disappearing as a result. The only basis for argument is whether or not this matters.
Edward Wilson, of Harvard University, and Theodore Roszak, of Californian State University, are both passionately convinced that it does matter, and in their new books - Wilson's "The Diversity of Life" and Roszak's "The Voice of the Earth" - they argue eloquently that it is time we mended our ways and took more account of the damage we are doing to the biosphere of our planet.
Their approaches, though, are very different. Roszak speaks with passion, from the heart; Wilson speaks from the head, writing with clarity and precision and never getting a fact wrong. The slight surprise is that Wilson's approach is the more compelling and persuasive, and makes for an enthralling read.
This is only a slight surprise because Wilson has already twice won the Pulitzer prize for his writings on matters scientific, and seems incapable of writing badly. He describes the diversity of life today and the means by which that diversity has evolved, and points to six occasions during the history of life on Earth when there have been great "extinctions", wiping out large numbers of species and setting that evolution back by millions of years. Five of those extinctions occurred between 450m and 65m years ago, the most recent of the five being the event that caused, among other things, the death of the dinosaurs. The sixth extinction is happening now. It is likely to be bigger than any of the other five and it is all our own work.
When the facts speak so dramatically, it is hardly necessary to become emotional about what is going on. Roszak's approach can best be summed up from the subtitle of his book "an exploration of ecopsychology". This is the Californian hippie view of impending catastrophe. He takes the concept of Gaia (the notion that the entire biosphere of the Earth can be regarded as a single living organism), and suggests that what is happening now is a result of a madness afflicting Gaia. But where Wilson starts with the facts and leads the reader to inevitable conclusions about the need for better stewardship of the planet, Roszak starts from an emotional belief in the need for good stewardship, and bends the facts to fit his preconceptions.
He lays blame for the Black Death of the 14th century, for example, solely on "a virus carried by a flea that rode on the back of a rat". He totally misses the now well-established point that the collapse of the later Middle Ages was caused first by a climate shift, bringing cool, wet weather that destroyed harvests and left populations starving and vulnerable to the infection. And although he correctly identifies a shift in the thinking of scientists today, away from the clockwork of Newtonian mechanics, he describes the "new physics" of Planck, Bohr, Heisenberg and others as "tearing down the remaining ramparts of materialism" at the end of the 19th century. Bohr was only born in 1895, and Heisenberg not until 1901; hardly surprisingly, the revolution they led actually took place in the 1920s. This inaccuracy is typical.
In view of the way he seems eager to move the quantum revolution back a generation, it is surprising that Roszak seems unaware of a new revolution taking place today. Discussing evolution, he leans towards the mystic, saying that natural selection "is exactly the way life might be installed on Earth" from outside, and claiming that "there is no form of natural selection that resulted in the presence of such life-supporting necessities as the water on the globe". In fact, there is, but it requires extending the Gaia concept outwards, to embrace whole galaxies of stars rather than individual planets and Roszak's understanding of matters astronomical is distinctly sketchy.
Most infuriating of all, however, is the way in which Roszak ignores the work with which Wilson won his first Pulitzer prize. This concerns sociobiology, which offers an explanation of the way people behave in terms of the evolutionary pressures experienced by our ancestors. It is no good saying, as Roszak does, that the ills of the world are caused by the way we bring up boys and girls differently, without addressing the question of why boys and girls are different.
The "root of our environmental dilemma" may well be linked to the fascination young men have for movies such as Terminator and Robocop, as he suggests; but the reasons why boys like such movies has as much to do with the success of an African ape in becoming civilised as with the lack of "a female and feminist Freud" to change the way we think. The woolly thinking, imprecision and errors that riddle this book mean that it will do as much harm as good in the fight to save the planet.
Woolly thinking, imprecision and errors are, though, completely alien to Wilson's work. He is entranced by all forms of life, including the "cookie cutter shark", which gets its name from its habit of biting circular chunks of flesh from the living bodies of porpoises and whales. He also writes lyrically of the delights of sitting in the dark in a clearing in the rainforest, fitfully lit by the lightning from an approaching storm, using a torch to spotlight the wolf spiders out on the prowl for prey.
But the heart of Wilson's book is the final section in which he explains, more clearly than I have ever seen it explained, the true value of the diversity of life. It has become a cliche to talk of the possibility of finding new drugs (such as aspirin) and new foodstuffs (such as potatoes) in the diminishing rainforest. Wilson demonstrates how soundly based these possibilities are, and draws attention to the already known food plants that are at present enjoyed by Amerindians, but which have outstanding worldwide potential as crops.
The message of Wilson's story is almost unbelievable. About 1.4m species of plants, animals and micro-organisms have so far been identified and given scientific names. But at least 10 times as many species, and possibly as many as 100m, remain to be identified. Calling for a great effort to find out just what species we share our planet with, and referring to them as "unmined riches", Wilson points out that the effort would cost about half as much as the current project to map the human genome, and only a fraction of 1 per cent of the cost of a manned expedition to Mars.
He leaves the reader in no doubt that humankind has got its priorities seriously wrong, and that there may indeed be a madness afflicting Gaia. But this is not a polemical, proselytising book. It is a calm, thoughtful appraisal of the diversity of life on Earth - an appraisal which could all too easily become an obituary. If you only plan to read one science book this year, read this one.
