Ask biologists how many species live in a pond, a grassland, a mountain range or on the entire planet, and the answers get increasingly vague. Hence the wide range of estimates for the planet's biodiversity, predicted to be between 2 million and 50 million species.
A new way of estimating species richness reported this month in the journal Ecology Letters by University of California, Berkeley, ecologist John Harte and colleagues, will make such estimates more precise for habitats of all sizes and types, from deserts to tropical rainforests.