Causal Loop Diagram

Systems can be defined simply as a collection of connected things, that is, a set of elements that influence one another.

Modeling dynamics systems can be a complex task. Thus, there are tools that can be used to

structure it as a tangible dynamic system and facilitate the understanding of the problem. The present post will embrace one of these tools, the Causal Loop Diagram.

A Causal Loop Diagram consists on a chart that relates specifically the variables of a system and the variance on it caused by external disturbs. For a good flowchart it is necessary to choose wisely the variables, to know how they interact with each other, and how they are affected by exogenous variables.

Most of the system structure and baseline conditions can be illustrated by means of a Causal Loop Diagram.

To create a Causal Loop Diagram, find the variables associated with the system and determine which of these variables are related to other variables, define if the effect of one variable on another is positive or negative. The addition symbol (+) indicates that when the variable down the arrow increases, the one near the arrowhead also increases. The decreasing sign (-) indicates that when the first variable increases the second variable decreases.

In the case of Marine Population we divided the variables in two groups, Human Causes and Natural Causes, then related how these variables interact with each other and what could be the possible effects of these interactions on the system. The water temperature may be affected by the changes of the system, and this might lead to variations in the marine environment.