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The State Variable
A quantity that can be used to describe the condition of a system is called a “state variable”. When we talk about the “behavior” of a system, we are really talking about how its state variables change, usually over time, but sometimes from one location to another. Most systems will require many state variables to completely describe the state of the system; however, to keep things simple and focused, you should challenge students to identify a single state variable that can serve as a good overall indicator of the condition (good or bad) of the environmental system they have chosen to study. Encourage them to adopt the most obvious indicator they can find.
Kendra is concerned about coral reef health, so for her an obvious state variable is “coral reef health.” There are a number of ways this could be quantified. For example, Kendra learns through her library research that some scientists quantify coral reef health by looking at the fraction of reef area covered with live coral (versus dead coral, algae, rock or other things). |
