Biodiversity is a shorthand term for biological diversity, or the rich variety of life on Earth.
Remarkably, we are just beginning to map life's diversity. Scientists have identified 1.7 million living species, each a unique and irreplaceable product of evolution. But many species-rich ecosystems, including tropical forests, coral reefs, and the deep ocean floor, have been barely explored, and the best estimates are that we share the planet with between 3 and 30 million other species. Indeed, many previously unknown species, including some new birds and mammals, continue to be discovered each year. The ongoing effort to map the world's biodiversity takes on a special urgency in light of the serious threats facing many ecosystems.