Borneo is the third largest island in the world. Its rain forest is one of the most biologically diverse places on Earth. It is home to 90% of the world's orangutans. But in recent decades, deforestation has threatened the livelihood of the forest and its species, especially as trees come down to make room for palm-oil plantations. As conservation efforts are stepped up, visitors can still experience an abundance of wildlife with a variety of eco-friendly touring options. (HEINRICH VAN DEN BERG/GETTY IMAGES)