No ecosystem exists independently of the others. Though cities take up only about 2 percent of the actual land area on earth they have influences far greater than their size would warrant. These new cities are also the ecosystems with the greatest dependence on their neighbors. Each of these ecosystems on earth has its own structure and its own dynamics. Common to all, however, are two important traits.
Every ecosystem has a dynamic structure, a unique web of life.
The stability of this web comes from the hundreds of thousands of connections of living organisms one to another and to the non-living atoms and molecules at their base. No ecosystem stands still. Every ecosystem is always changing, is always evolving, is always related in critical ways to all the other ecosystems in the biosphere, and in the 3rd millenium is always changing in response to the most dominant species of the biosphere, Homo sapiens. Let's look at each of two traits in detail. The life web of an ecosystem is built on the base of a steady energy flow and a continual recycling of matter.