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.
Mammals make up one of the smallest groups, with just 5,513 members. Altogether the earth's oceans, lakes, continents and islands support over 66,000 identified species of vertebrate animals and more than 307,000 species of plants. How many species known to currently exist in the world. Category.