9. Greater Blue Mountains, Australia

More than 100 types of eucalyptus trees grow in these mountains. They respond to the heat by giving off oil into the air to form a particular blue haze. This kind of oil is inflammable, which is easy to bring forest fires, which are a natural part of the ecosystem. But the increasing wildfires caused by global warming may endanger the rare, ancient species here.

Greater Blue Mountains [huanqiu.com]