The cloud forests of the Sierra Nevada de Santa Marta national park of Colombia are most irreplaceable nature reserve on Earth. They have been threatened by drug growing, herbicide spraying to kill the drug crops and now housing developments. Valuable species include the critically endangered harlequin frog, the unicolored oldfield mouse and the green and orange Santa Marta parakeet. Area: 4,050sqkm The most irreplaceable nature reserve on Earth is the cloud forests of this high peak. They have been threatened by drug growing, herbicide spraying to kill the drugs and now housing developments