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.
Mathematician, computer science expert and animal rights advocate Brian Tomasik has attempted to catalog estimates of the number of individual animals in a variety of groupings. According to his data, the total number of individual animals on the earth adds up to approximately 20,000,121,091,000,000,000. This can be written as 20 quintillion, or 20 billion billion.