Conditions that promote karst development are well-jointed, dense limestone near the surface; a moderate to heavy rainfall; and good groundwater circulation. Limestone (calcium carbonate) dissolves relatively easily in slightly acidic water, which occurs widely in nature.
Crowther said first he had to figure out how many trees are on Earth and that number was far more than anyone expected: 3.04 trillion trees, according to a study published Wednesday in the journal Nature. 14 Photos Trees Around The World.
Believe it or not, there are about 950,000 species of insects. No one knows for sure how many species of animals exist on Earth. In fact, some 10,000 species of animals are discovered each year, with over one and a half million species already described. Projections for the total number of species on Earth range from 2 million to 50 million.