The environmental version of the Kuznets curve

ECONOMIC growth is generally assumed to be bad for biodiversity. That is right—but only up to a point. In the early stages of a country's growth, the human population increases sharply, natural habitat is lost and pollution rises. But when countries approach middle-income level, that starts to change, for several reasons: some of the effects of growth (such as sewage systems and restrictions on factories' freedom to pollute) benefit other species as well as humans, population growth rates fall, people press governments to clean up their act and governments work better. This scatter chart, which uses change in forest cover as a proxy for the health of biodiversity, neatly illustrates the effect of prosperity. Poorer countries tend to chop down forests, richer countries to plant them. The turning point, on average, is around $18,500. Read the full biodiversity special report here.