Code Blue, Endangered Oceans

A PopEd Interactive Story

One of the ways to engage a group of any age is through an interactive story. This is what PopEd has created to educate middle and high school students about human impacts on the oceans through history. Participants help tell the story through simple props that create a visualization as the story is being read by the teacher or facilitator.

Code Blue: Endangered Oceans was developed for our World of 7 Billion educational campaign four years ago and has become one of our most popular activities for teacher workshops. While there are certainly useful teaching tools from other organizations that examine ocean health and human activities, this is the only one we’ve seen that clearly makes the connection to population growth.

Set Up

The central visual element for Code Blue is a clear bowl or rectangular container of water. This should be situated where everyone in the class can see it. Each student receives a canister containing a substance that represents something that gets added to oceans (e.g. green yarn for algae blooms, cooking oil for oil spills, vinegar for acidification, floss for abandoned nets, coffee grounds for untreated sewage, etc.) or a character card representing something that gets extracted (whales, marine birds, coral reefs, etc.). A duplicate set of character cards are taped to the bowl. Next to the bowl are 14 clothespins, each of which represents half a billion people.

Facilitating the Activity

The teacher explains that she will read a story about the history and health of our oceans, and that students will listen for the name of the character printed on their canister or card. When they hear it, they will come up to the water bowl and pour in the contents (if they have a canister) or pull off the matching character card.

The teacher then reads the story, adding emphasis and pausing on the words in bold so that students remember to add their pollutant or remove their character. As the teacher reads, she adds a clothespin whenever 500 million people are added to the human population, as the years advance from 1500 to the present.

The Story

The story begins 500 years ago, when the global population was about 500 million (1/14 of what it is today). So, one clothespin gets attached to the bowl right away. The reader tells the group that the oceans have changed a lot since 1500 and that this is a story of those changes. Interactive story points include these events:

  • Beginning in the 1600s, and lasting for about 200 years, harpooning decimated whale populations, as demand for whale blubber (to convert to oil) grew.
  • In the early 1800s (when the population reached 1 billion), chemical fertilizers were introduced to increase crop yields; the nitrogen runoff caused algae blooms, which created ocean dead zones.
  • The Industrial Revolution in the mid-1800s introduced coal as the new source of energy. When burned, coal releases mercury, which fish ingest and then pass along to humans when eaten.
  • The early 1900s saw the digging of the first off-shore oil wells; oil spills have been a threat to oceans ever since. World population reached 2 billion in 1930.
  • By the 1950s (there are now 6 clothespins representing 3 billion people), the use of new fishing technologies led to overfishing and bycatch.
  • The advent of aquaculture in the 1970s (when population reached 4 billion) decimated coastal ecosystems and caused antibiotics (given to the farmed marine animals) to pollute ocean waters.
  • As the population reached 5 billion in the late 1980s and then 6 billion in the late 1990s, plastic litter was beginning to kill marine birds.
  • The population reached 7 billion in 2011. By this time, climate change had already begun causing ocean acidification (leading to the death of coral reefs) and sea-level rise.

By the story’s end, the bowl is a murky mix of all the “pollutants” students have added to the water; the cards representing a variety of sea life have been removed; and 14 clothespins sit on the perimeter of the bowl.


The activity includes questions to help students process the demonstration and use critical thinking skills.

  • Who polluted the ocean?
  • What effect did increasing population have on the health of the ocean?
  • Think about the pollution held in the canisters. Could something be done to prevent those types of materials from entering the water?
  • Think about the organisms that were removed or destroyed due to human activities. They aren’t confined to just one area of the world, but swim freely around the globe. Who owns these animals? Who should manage how many of these creatures people are allowed to remove? How can these management systems be enforced internationally?
  • Were all of the inputs caused by humans? Which ones were? Which ones weren’t?
  • Think about the impacts of sea-level rise in coastal communities. Where will these impacts be the worst?
  • Do you think that it is easier to prevent pollution by managing ocean resources beforehand, or to clean it up and restore it later?
  • What could each of us do to help improve the health of our oceans?

Follow-up Activities

Have students research the piece of the story that seemed the most interesting or relevant to them. Or, have a discussion about international policymaking. What are the difficulties of getting countries to solve problems together? What is the best method of solving these problems? Have students research an international policy or regulatory body of their choice (Montreal Protocol, Kyoto Protocol, Intergovernmental Panel on Climate Change, International Whaling Commission, or the Convention on International Trade in Endangered Species). Ask them to write a short paper on the history of the policy, which countries were major players in the debate, and why it was important or controversial. Alternatively, they could work in groups and give a short presentation to the rest of the class on their treaty or commission.

The full activity and story script for Code Blue: Endangered Oceans is available for free download at


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