disappearing in sandy deserts. In all of them, one finds the same forces of nature at work, making for the slow carving out of valleys and for the enrichment of plants and wildlife.
Everywhere there is a delicate balance among water, soil, plants, and animals. Man can change this moving balance of nature for the good by stabilizing it at new levels and by adding new harmonious elements, as when he stores the water of ephemeral streams to create green oases. Or he can throw it out of balance by selfish or ignorant use of resources, so as to set in motion a vicious chain of destruction, as when he slashes a forest and launches a whole new cycle of soil erosion.