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Should iron fertilization be used to mitigate global warming?

Elizabeth Gordon, Fitchburg State University


Students engaged in this activity examine the scientific and ethical dimensions of iron fertilization as a geoengineering strategy to mitigate global warming. Students will analyze data from iron fertilization studies to answer the scientific question of whether or not iron fertilization increases biological productivity and carbon sequestration. Students will then discuss/debate the ethical considerations of employing iron fertilization.


This activity is heading in the direction of use for an upper level course with mostly science (Earth Science, Biology, Chemistry) majors and minors. I also envision a modified (i.e., simplified) version of the activity that could be used for an intro oceanography class taken by mostly non-majors.

Class size: 15 to 30 students

Skills and concepts that students must have mastered
Students should already be familiar with basics of marine biological productivity and the carbon cycle; basics of the greenhouse effect and global warming, including how human activities contribute CO2 to the atmosphere and the current level of CO2 in the atmosphere. Some quantitative literacy skills (e.g., reading and analyzing a graph) would be helpful.

How the activity is situated in the course
stand alone exercise


Content/concepts goals for this activity
Explain the iron fertilization hypothesis
Describe the marine biological pump
Discuss geoengineering strategies to mitigate global warming

Higher order thinking skills goals for this activity
Quantitative reasoning, ethical reasoning

Other skills goals for this activity
Writing, critical reading, defending a position, working in groups

Ethical Principles Addressed in this Exercise

Students will be asked to consider the ethics of geoengineering in general, with particular focus on iron fertilization. This applies to Environmental Ethics by considering the ethics of climate change in general and the use of technology as a 'solution' to global warming. Advanced students would consider the complexity of the issue as it pertains to weighing the ethical dimensions of harm caused by global warming versus unintended consequences of iron fertilization. This scenario could also be expanded to include discussion of ethics in the geoscience profession –ethical considerations of performing large scale iron fertilization experiments in situ – but that is currently not covered within this activity.

Description and Teaching Materials

Working in groups, students will analyze data from several iron fertilization experiments (maybe as a jigsaw activity). The goal of this part of the activity is to have students evaluate the claim that iron fertilization would lead to carbon sequestration. Quantitative literacy outcomes include analyzing data, using scientific data to answer a question, and to discuss assumptions and limitations of scientific studies. As a take-home assignment, individual students would provide a written explanation of their scientific understanding of iron fertilization, and then be asked to consider if we 'should' add iron to the ocean to mitigate global warming. After completing the essay, students would discuss/debate in class their views on iron fertilization as a geoengineering strategy. The ethical reasoning outcomes include stating a position on an ethical issue, identifying stakeholders on an issue, and distinguishing between moral and non-moral arguments surrounding an issue.

Case Study Scenario

PDF of the draft scenario attached. FeFertactivityoverviewdraft (Acrobat (PDF) 116kB May30 14)

Teaching Notes and Tips

I'm in the process of developing this activity so it's hard to say at this point what the major obstacles will be. There may be some resistance to the idea that humans are contributing to global warming, but this could also make for interesting discussion. One content-related barrier that I anticipate is students making the mental leap from biological productivity in the surface ocean, which most intro students seem to grasp, to the amount of carbon that is finally exported to the deep ocean.


reflective writing and observation during class debate (rubrics to follow soon)

References and Resources

A couple of links to get started (more to follow):

Should iron fertilization be used to mitigate global warming? -- Discussion  

In addition to comments in discussion -

Highlighting the importance of scale - how much energy would it take to bring enough iron in the right form into the ocean to make a meaningful impact on CO2 concentration.

Look for analogous approaches, and how different analogies work more or less well.

What is the energy return on energy invested? - I've not quite phrased that correctly - I'm trying to get at life cycle analysis.

Attend to who gets to decide.


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Scientific Accuracy:

Alignment of Goals, Activity, Assessment: The activity is well aligned with the general goal. I'd like to see more about assessment, particularly the assessment of ethical reasoning skills: identifying stakeholders (including organisms on the ocean floor?), generating alternatives, imaging consequences (e.g., unintentionally people are encouraged to use more CO2), evaluating possible solutions using ethical values or ethics tests (e.g., benefits vs. harms).

Pedagogical Effectiveness: Seems appropriately challenging for advanced undergraduate students. Uses collaborative learning techniques. Reasonable, informed people could argue for either side of the issue. The case could be effective if students have learned some ethical reasoning skills earlier in the semester.

Robustness: It's good to recommend some references, but I am concerned that the Web links may become obsoleted in one or two years.

Activity Description: You might prompt students to identify missing information, e.g., how much energy is needed to produce the iron in the needed form and amount. You might explain more about how the instructor can conduct a jigsaw. Do emphasize that groups should be small, three or four students each. Also, note that "structured academic controversy" is a good alternative to standard debate format.


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