Sir

Sandra Knapp, in her Concepts essay about conservation, “Dynamic diversity” (Nature 422, 475), correctly and succinctly presents an analysis of a major conceptual problem facing conservationists: that preserving nature is not about stasis, but about maintaining the ever-evolving variety of life of Earth. Since the middle of the nineteenth century there has been abundant evidence that the Earth has been, and will continue to be, a complex, ever-changing series of habitats and associated species, of which we experience only a snapshot in our lifetimes. Our conundrum is that while we know this, we seem unable to take the required long perspective implied by Knapp's plea for a dynamic view of the natural world.

Why do we cling to this static view of nature, which is deeply embedded in popular understanding of the natural world as well as in the thinking of politicians and policy-makers interested in conservation and sustainability? This misunderstanding of the natural world can be summed up in a phrase that we constantly hear from the media, environmental groups, politicians and in casual conversation: “the balance of nature”. The idea that nature is, or should be, “in balance” is deeply ingrained. But there is not, and never has been, a balance of nature.

Balance is a seductive concept as it suggests that opposites can be equated and, in the final analysis, traded. But it is not possible to equate humans and elephants, woodlands and meadows, tonnes of carbon emissions with hectares of new forest, and so on, unless it is by reference to an arbitrary, external concept. In the marketplace, this arbitrary concept is money. Economists are now attempting to balance natural processes, habitats and species using the abstraction of their monetary value, on the assumption that cash can be the final arbiter of the difficult value judgements necessary for custody of the planet and its natural processes.

It is now surely time to abandon this way of thinking. We now need to embrace — in science, popular culture and politics — the phrase “the dynamic diversity of nature”. It may not be as catchy as “the balance of nature”, but wide exposure should eventually see it embedded in our lexicon of aphorisms.