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.
Reforestation standards are dictated by the Forest Practice Rules. For example, in western Washington, at least 190 trees per acre must be established within three years of harvest. Most landowners plant between 400-500 tree seedlings per acre. On average, 3 trees are planted for each tree harvested.