The Denver Zoo is accredited by the (American) Association of Zoos and Aquariums (AZA) and is also a member of the World Association of Zoos and Aquariums (WAZA). The zoo achieved ISO 14001 certification in 2009, was given the first AZA Green Award in 2011, and was named the "Greenest Zoo in the Country" at the World Renewable Energy Forum in 2012. In 2015, it was re-certified for ISO 14001 and achieved OHSAS 18001 certification, becoming only the fourth zoo in the world to get both certifications.