A New Way to Think About Cause and Effect Chains With Application to Coastal Hypoxia and River System Ecology

Many ecological and fisheries questions, especially those with management implications, involve chains of cause and effect relationships that span multiple academic disciplines or scales of analysis.  For example, river nutrient loading and water column stratification combine to cause Gulf of Mexico hypoxia, it is proposed that hypoxia in tern effects Gulf fish populations, and fisheries catches, however, not all of these relationships are known with equal certainty.  The interdisciplinary teams assembled address these questions must be able to clearly communicate among themselves and with managers, despite often speaking different disciplinary languages.  Numerical models can be used to propagate causal relationships with high precision; however, building understanding from these models is often hampered by the details.  I will present a simple graphical method for discussing and conveying the outcome of sequential cause and effect relationships, regardless of functional form, and allowing for communication of conditional outcomes, natural variation, and scientific uncertainty.  Experience in multiple teams has shown that this method is useful for building group consensus on study implications, selecting particularly uncertain and important relationships for further study, and finding meaningful indicators of environmental quality.