THE NATURAL ENVIRONMENT

Happily for life on Earth, the planetary greenhouse effect warms Earth enough that the surface is covered with mostly liquid, rather than frozen, water. Every living thing depends on the liquid state. And it is everywhere. Average two-mile deep oceans cover 71% of the planet, the ground is saturated with it, lakes and rivers network the land, it fills the skies with clouds. In its frozen state, ice layers kilometers thick bury polar land surfaces and glaciers cover high mountains.

In this chapter, we look at water in the environment, how it moves between reservoirs, sources and losses from the surface, and the more important aspects of water availability to humans, especially in Hawai'i.

We also look at another essential resource for life: soil. Historically, it has been the quality of soil that has determined human occupation and explained where the world's great population centers were located.