The Wetlands MEL

The Wetlands MEL asks students to consider different viewpoints on the uses of wetlands, a socio-scientific issue. Some people value what wetlands offer the local environment, such as habitats for all types of organisms and a place for floodwaters to collect away from where people live. Others perceive them as property to develop or as a breeding area for mosquitoes. The Wetlands MEL uses two different conceptual models of a socio-scientific issue that focus on value to society, as opposed to two different models of a scientific phenomenon.

Below are links to resources that will help students use the Wetlands MEL and learn more about the competing views of wetlands.


This article provides an introduction to the Wetlands MEL plus suggestions from classroom use including implementation advice, insights into the lines of evidence that challenge students' thinking, and the rationale for using MEL diagrams to address socio-scientific issues that focus on value to society.

Wetlands: Good or Bad? TES (Acrobat (PDF) 388kB Jun4 18)

The Models

Model A: Wetlands provide ecosystem services that contribute to human welfare and help sustain the biosphere.
Model B: Wetlands are a nuisance to humans and provide little overall environmental benefit.

Student Handouts

Lines of Evidence

Evidence #1: Wetlands play a role in the global cycles of carbon, nitrogen, and sulfur. Wetlands change these nutrients into different forms necessary to continue their global cycles.
Evidence #2: Flooding is a natural occurrence in low-lying areas and wetlands are places where floodwaters can collect.
Evidence #3: Wetlands contribute 70 percent of global atmospheric methane from natural sources.
Evidence #4: Many wetlands are located in rapidly developing areas of the country.

Student Handouts

Other Resources

This Plausibility Ranking Task (PRT), which may be completed prior to using any MELs, helps students to understand the role of evidence in supporting or refuting models.

The Explanation Task is part of each MEL Activity. In this task, students provide written explanations for the arrows they draw on the diagram. The following rubric may be used to score students' written explanations.