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The following review of the spatial extent of life to be acted upon is organized along the same lines as the Discovery Channel's excellent "Planet Earth" documentary,3.198 going from polar ice worlds to deep seas to shallow seas to fresh water to
jungles to deserts to prairies to forests to mountains and finally to caves.
Of the two polar ice worlds, Antarctica has the least life today. It is a cold desert. About 98% of the continent is covered by thick ice sheets averaging a mile in thickness (1.6 km). The other 2% of the surface area is barren rock. Temperatures reach a minimum of -90oC (130oF) in the interior in the winter and a maximum of +15oC (59oF) near the coast in the summer. Only very cold-adapted plants and
animals survive, including penguins, fur seals, mosses, lichens, and algae.3.199 However, Antarctica has not always been so devoid of life. The British Antarctic Survey (BAC) manages an archive of over 100,000 rock and fossil specimens from the continent.3.200 Before spreading centers moved the geologic plates so Antarctica is now located at the south pole, the continent was at much more temperate latitudes and life was abundant, as is shown in the fossil record.
By comparison, the north pole centered Arctic is teaming with life. The July isotherm, which generally corresponds to the northern tree line, is one definition of where the Arctic starts. A key factor in the more abundant life is the land connection to North America, to Greenland, to Scandinavia, and to Asia. The treeless frozen ground teems with life, including organisms living in the ice, fish and marine mammals, birds, land animals, as well as human societies. Plants include dwarf shrubs, herbs, lichens, mosses, and a few scattered grasses. Animals include polar bears, wolverines, arctic foxes, ptarmigan birds, beluga whales, arctic wolves, ringed seals, lemmings, arctic hares, and mankind.3.201 Underneath the permafrost, extensive gas hydrate deposits, believed to be largely derived from ancient life. Although life is much more extensive than in the Antarctica desert, it is still sparse compared to life in a rain forest. Volumes of life in
the arctic are more comparable to volumes of life at the bottom of the oceans.
The Deep Seas consist of lowest layer in the oceans,
the layer below where sunlight penetrates and heats up the water. The waters are colder, more salty, and under high pressure than anyplace else on earth. This combination makes a tough environment for life to flourish. Most organisms living below where sunlight penetrates rely on falling organic matter for subsistence. Life is sparse, and life is exotic.3.202
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paradoxes