Inside ecosystems - urban ecosystems

American Forests, March-April, 1995 by Gary Moll, Ed Macie, Bob Neville

Everybody and everything lives in one community or another. Your community may be in a city, the suburbs, or in a rural area, and it may be big or small. Most of us think of community in terms of social conditions, but it also has a biological meaning. A community is a place where plants and animals share the same environment; it is both a social and an ecological unit.

This issue of Urban Forests is the third in a series featuring one community - the urban ecosystem. The October/November 1994 issue defined and described an urban ecosystem. We dedicated the December/January 1995 issue to people, the "megafauna" of the urban ecosystem.

Here we tackle the inner workings of an ecosystem and the links that connect its elements. One of the most prominent links is the one between people and the environment. As "megafauna," we are the ecosystem's - indeed, the earth's - only creatures with the ability to think, communicate, understand, and act upon complex issues. Sit back as we engage these unique human abilities to continue our ecological journey.

Imagine you are entering a room. On three walls, sheer white curtains hang to the floor over long, narrow windows. Late afternoon sunlight gives the hardwood floor a satin glow. In the center of the room is a square table with two chairs. A tall, thin man sitting in one of the chairs asks you to join him in a game. There is a familiar black-and-white checkered gameboard on the center of the table and chess pieces grouped at either side. You sit and nervously sort through the pieces at your end of the table as your polite, soft-spoken opponent starts explaining the rules.

The lights dim, obscuring the board's sharp features. Your opponent puts his hand on the board and then both rise a foot or more above the table, as if the board is magnetized to his palm. Several other boards are visible below.

It now appears that a three-dimensional chessboard has been placed before you. The layers are not the standard black and white of a checkerboard but rather the moving colors of a living landscape. One level is blue, representing water in the form of rivers, lakes, and streams. Another is green, showing trees, shrubs, and other vegetation. A third layer has buildings and roads; another has clouds, smog, and other elements of the air. Obviously, this game has an ecological twist.

"Time to put the pieces into play," announces your opponent. But instead of pawns, rooks, and knights, your game pieces now look like people in different sizes, shapes, and colors. Your opponent advises you that the pieces can move in any direction; there are no standard moves. Moving one usually triggers a combination of moves by other pieces, but the rules about "triggered combinations" are vague. The pieces can move up and down, from one level to another, and the actions they take on one layer will penetrate the other layers above and below.

Your opponent provides a valuable piece of advice: "Don't get lost in the details; keep your mind on the game as a whole. Watch what happens to a layer of the board. When a piece moves, the features on the board will change. After a few games, you will come to understand how your moves affect the changing landscape. Just remember, the layers are connected - they are all one board. The landscape has been separated into natural features so we can play our various scenarios and see the impact of an action on the landscape. We can collapse the layers and play the game on one level if you wish."

He places his hand on the uppermost level and pushes it back into the table in one piece. The blues and greens blend into a lush landscape. The squares are barely visible.

The man looks straight at you and says calmly, "We are not opponents; we are partners. We play as a team. We challenge the board. We try to keep the greens green and the blues blue." Suddenly you understand. This is not a game - it is land-use planning. It is public policy in the making. The scene fades to black.

The Urban/Rural Gradient

This fascinating layer game can be helpful in understanding urban ecosystems. A living landscape - your city or town, let's say - can be divided into land-use features. Much like the 3-D chess game, the landscape can be separated into feature-specific layers - one for soil, one for water, one for vegetation, and one for structures.

A typical landscape, which consists of urban, suburban, and rural ecosystems, is called an urban/rural gradient. These distinctly different ecosystems are not attached to each other, but they are linked. Suburban areas, small towns, and urban/rural intermix areas are the connecting zones. They connect both the physical landscape and the social conditions of people.

Feature layers help explain the connections and links that occur in an ecosystem as change occurs. The combination of feature layers superimposed on the rural/urban gradient allows you to follow an action and the corresponding reaction.

The rural, suburban, and urban areas can all be considered separate ecosystems, but they are not islands. All systems are connected to each other - neighboring systems have many obvious links; links between areas distant from one another may require some investigation. Urban and suburban systems are closely linked and urban and rural systems have distant links. Rural and urban systems are connected most visibly by streams (hydrologic feature). Actions that affect a stream resonate throughout the entire gradient.