China's incredible ‘Heavenly Pits’ (also called Tiankeng) are the result of carbonate bedrock dissolved over time by underground water. As these underground rivers carved large caves, they finally collapsed, creating vertical chasms, or giant dolines, 500 to 600 meters deep. These areas are like giant greenhouses - they trap heat and moisture so that the climate is stable and humid. The absence of outside winds, along with extreme temperature changes from day to night, provides a perfect environment for ancient forests, as well as a unique type of biodiversity. According to the scientific community and UNESCO, the deep karst landscape provides a ‘thermal buffer,’ allowing many rare species to thrive in distinct primitive ecosystems that act as prehistorical biological refuges. Shielding these habitats from external climate shifts, these sinkholes preserve ancient plant lineages that have vanished elsewhere on Earth.
