Biological diversity, or biodiversity, refers to the variety of life on Earth. As defined by the U.N. Convention on Biological Diversity, it includes diversity of ecosystems, species and genes and the ecological processes that support them. Natural diversity in ecosystems provides essential economic benefits and services to human society—such as food, clothing, shelter, fuel and medicines—as well as ecological, recreational, cultural and aesthetic values, and thus plays an important role in sustainable development. Biodiversity is under threat in many areas of the world. Maintaining global biodiversity has emerged as a prominent and widespread public issue.