3.5. Causal loop diagram
In system dynamics, causal loop diagrams are used to show the major feedback mechanisms by exhibiting the structure of the modeled system. The diagrams consist of elements of the studied system, arrows linking the elements and a “+” or “−” sign on each link that conveys information about the relationship between the elements (see Fig. 6). A positive link is between elements that change in the same direction, i.e. an increase of one A 943931 causes an increase of the other element. A negative link shows that elements change in the opposite direction, i.e. an increase of one element causes a decrease of the other element. A cross-marked link denotes a delay between cause and effect, i.e. time is necessary to observe the effect caused by an element.
Fig. 6. Causal loop diagram of the structure of the modeled agricultural system.Figure optionsDownload full-size imageDownload as PowerPoint slide
Also a complete feedback loop is death rate given a designation. A loop denoted by “R” indicates a reinforcing loop — an initial disturbance leads to further change, thus a change in one direction causes even more a change in the same direction leading to exponential growth or collapse. A balancing feedback loop, denoted by “B”, has a stabilizing or goal seeking behavior — after a disturbance the system seeks to bring conditions into equilibrium state. When reinforcing and balancing loops are combined, the complex behavior of the system appears. In a sense, causal loop diagrams are as simplified maps of the connections in a closed loop system of cause and effect relationships.