ABSTRACT
The first-generation atmosphere changed slowly and begot the first, simple forms of life, forms of life that could survive only in the sea because the harsh, intense, primordial sunlight destroyed all unshielded cells. For the natural systems of Earth—the multifarious ecosystems, the grand biogeochemical cycles, the spectacular array of biomes and species—are the primordial interdependence. The immense flow of solar energy propels the atmosphere in a complex pattern of winds, determining weather and climate and driving the ocean’s circulation in patterns linked with those of the atmosphere, and it propels all of life as well. The atmosphere is a thin and fragile membrane, a ubiquitous mediator between sea and land, tropics and poles, the, organic and the inorganic, animals and plants, one ecosystem and another. The oceans, coastal marine environments, rivers, and freshwater wetlands—even the atmosphere and dry-land terrestrial ecosystems—are integral components of the hydrologic cycle.
