In 2009, the zoo achieved ISO 14001 certification and the Denver Zoo was named the "Greenest Zoo in the Country" at WREF 2012.
The zoo achieved. This was in 2009. ISO 14001 certification was named the "Greenest Zoo in the Country" at WREF 2012. The Denver Zoo was named the "Greenest Zoo in the Country" at WREF 2012.