Greater biodiversity in ecosystems, species, and individuals leads to greater stability. For example, species with high genetic diversity and many populations that are adapted to a wide variety of conditions are more likely to be able to weather disturbances, disease, and climate change.
Greater biodiversity also enriches us with more varieties of foods and medicines. Current estimates of global species diversity vary between 2 million and 100 million species, with a popular estimate of somewhere near 13 to 14 million. The majority of them are arthropods. But very little is known about most species.
Only roughly 1.5 million species have been described, and only 40,000 to 50,000 species have had their conservation status assessed. Roughly a third of these are believed to be at some risk of extinction.