Importance of Edges and Boundaries

Discussion

Dave Braden:

"So far we have looked at the Living System on this Planet as a pattern of interactions among all the organisms alive at any given time. We have talked about that pattern of interactions generating the oxygen we breathe, much of the water that falls as rain, the organic molecules we use as food, the goods and services we buy and the information we use to navigate the pattern. In this lesson we look deeper into the pattern to examine the details of how interactions create flows.

Every interaction requires an edge between one thing and another. The flows of oxygen, water, nutrients, goods and services, and information are generated on one side of an edge and flows across the edge. Reducing the edge reduces the flows. This lession will look at how some of our most common practices reduce edge in the pattern of interactions among living things. We can also learn to increase edge in the pattern. Increasing the edge increases the flows.

Consider a living cell. On the inside of the membrane a set of processes is taking place. On the outside of the cell’s membrane there is a different set of processes. The interactions on the inside of the membrane produce certain chemical compounds. The build up of compounds on one side of the membrane creates a pressure to cross to the other side. This movement across the membrane is a flow across the edge. These flows are what we mean by the flows through the pattern of interactions. Increasing the flows requires increasing the number and variety of edges.

The outside of an organism has surface area. The surface area is the boundary between the organism and its environment. The edge of a leaf has surface area. The surface area of a leaf exchanges oxygen, carbon dioxide and water with the air. The inside of a small intestine has surface area. The small intestine absorbs nutrients from the food and liquid flowing through it. Reducing the surface area reduces the volume exchanged. Increasing the surface area increases the volume exchanged.

Sometimes we call the edge a boundary. There is a boundary, with surface area, between biological communities. There is a boundary between a forest and prairie, between a wet land and pond, between fresh water and salt. There is a boundary between ecosystems in succession. There is a boundary between a climax forest and a burn scar, between a hillside ecosystem and a landslide down the hill, between a newly plowed field and a neighboring field in fallow. There is a boundary between human settlement and ecosystems in succession. Each boundary separates one set of interactions from another set of interactions. The different products of each set of interactions sets up a pressure for exchange across the boundary." (http://www.livingsystemsinst.org/edge?)