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. Species and ecosystems provide a wealth of essential goods and services upon which human well-being fundamentally depends. Many insects, birds, and bats, for example, pollinate flowering plants, including agricultural crops.
Rhizobial bacteria convert atmospheric nitrogen into nitrate fertilizers in a form usable by plants.
And wetlands serve as sponges to reduce the impacts of floods and to cleanse streams by filtering sediments, nutrients, and contaminants from inflowing waters. Essential goods come in the form of foods, fuels, fibers, and medicines. Cyclosporin, an important suppressor of immune responses, was derived from a relatively obscure fungus found in Norway. But the vast majority of plants, fungi, and microorganisms have yet to be tested for potential medicinal properties, and the opportunities for doing so are being irreversibly diminished. Similarly, the wild relatives of major agricultural crop plants provide important sources of genes for increasing the resilience of agricultural systems to effectively cope with changing climates and outbreaks of pests and diseases.