A small boy hauls enthusiastically on his fishing rod. The line flies up and a needle-spined fish strikes him in the eye. Desperate to stay outdoors, he ignores the pain, but his sight deteriorates over the following months. He continues to pursue his love of nature but, now blind in one eye, he is confined to studying creatures that are easy to see: insects. He grows to become the global authority on ants, and in later life is given the moniker “the father of biodiversity.”
The man is E. O. Wilson, the eminent American biologist. In his book The Diversity of Life (1992), he described biodiversity as an assemblage that “has eaten the storms—folded them into its genes—and created the world that created us. It holds the world steady.” We tend to think of biodiversity as a landscape of teeming jungles and coral reefs, its destruction manifesting as forest clearance and species extinction. However, these images don’t capture the full significance of the equilibrium that Wilson described. Biodiversity is not just the abundance of life on Earth. Rather, it is what maintains the resilience and flexibility of the environment as a whole, so that life can weather the inevitable storms.
The global Convention on Biological Diversity defines its subject as variability among living organisms at three different levels: within species, between species, and of ecosystems. The first diversity, within species, is at the level of the gene. A species is made up of individuals. For example, the 10,000 or so species of ant are estimated to comprise a staggering 10^15 individuals. (That’s 1 followed by 15 zeroes!) With the rare exception of twins, each of these individuals will have their own unique combination of genes. If we destroy half of the ants in each species, we will still have 10,000 kinds of ant, but we’ll have lost 50 percent of each species’ genetic diversity. In recent history, many species have been reduced to far smaller numbers. Pre-Columbus, 25 million bison roamed the plains of North America, but by the late 1880s fewer than 100 remained in the wild. Although conservation interventions have since increased bison numbers to the hundreds of thousands, the genetic diversity that was lost can never be recovered.