The great loopings and returns of life-giving substances through the environment. The three most important are the gaseous (e.g., the carbon, oxygen, and nitrogen cycles), the sedimentary (including the phosphorus, sulfur, calcium, magnesium, and potassium cycles), and the hydrologic (water vapor to rain to streams to oceans to vapor). Uninterfered with, these cycles tend to be self-organizing and self-renewing.