EarthLabs > Climate and the Carbon Cycle: Unit Overview > Lab 2: Carbon on the Move! > 2C: What's the Feedback?

The Carbon Cycle: What Goes Around, Comes Around

Part C: Systems Thinking and The Carbon Cycle

When you took your carbon journey through the carbon cycle, you moved through a complex system of processes and reservoirs with many changes along the way. Understanding the carbon cycle and how it behaves requires that we think of it as a complex, dynamic system A web of interconnections that creates emerging patterns. with components of the system interacting with each other in often unpredictable ways. Looking at the complexity of systems is called systems thinking and requires habits of a system thinker.

Think of a complex system like a large high school. What if one day every student that walked through the doors received a laptop for their own personal use in class with unlimited access to wireless? How might this one change cause other components of the high school system to change? Think about it!

The Connections GameUnderstanding Complex Systems

How can we demonstrate that parts of a system are interconnected and that changes to one part of the system can cause changes to other parts of the system? To help us understand this concept, we are going to play the Connections Game, developed by systems thinkers Rob Quaden, Alan Ticotsky and Debra Lyneis in The Shape of Change. In the Connections Game, you and your fellow students will each be playing one component of a system. What will happen to other components of the system if one component should change?

Connections Game Materials:

A number card large enough to be visible to other students.

Connection Game Instructions: (adapted from The Shape of Change)

1. Demonstration: Understanding the term "equidistant" is critical to playing this game. The teacher will ask two students to help demonstrate what it means to be equidistant from two other players. Can one person move and still be equidistant from the other two people?

2. Your teacher will give each student a number card.

3. Stand in a large circle with your numbers held in front of you so others can see.

4. Look around the room and randomly choose the numbers of two other players. These will be your SECRET equidistant partners. DO NOT tell anyone who they are!

5. When your teacher gives a signal, move to a point that is equidistant from your two partners. Do this with NO talking.

6. Keep playing the game until all players are equidistant from their two partners and the movement stops.


Think of the people in the Connections Game circle as a complex system.
  • How did the system behave when you tried to stay equidistant from your two secret partners?
  • How did one person's change in position affect others in the group?
  • Could a change in one part of the Connection Game system cause a cascade of changes in other parts of the system? If so, how?
  • How will understanding how a Connection Game system behaves help you understand how a very complex system like the carbon cycle might behave if changes occurs anywhere within the carbon cycle system?

Connection Circles - Identifying Causal Connections in The Global Carbon Cycle

Part 1: Identifying Causal Connections.

(adapted from The Shape of Change)

Now that you know a change in behavior in one part of a system can cause multiple changes in other parts of a system, the next step in systems thinking is to look for causal connections Cause and effect relationships between parts of a system. A change in one part of a complex system can cause changes in other parts of the system. between these changes. Causal connections are another way to describe "cause and effect" relationships. Systems thinkers use Connection Circles as a graphic tool to identify and understand changes and their causal connections in complex systems. When thinking about causal connections, it is helpful to think about them in "If....then " statements. The "If.........." represents the cause; the "then......." represents the effect.

With a partner or group, read the "If...then" statements below. Complete each causal connection. Keep in mind that there will be several possibilities for each of these "If...then" statements. In addition, think about these causal connections in terms of the carbon. When you are done, share your causal connections with the rest of the class. The first one has been done for you as an example:


In complex systems such as the carbon cycle, causal connections are are often circular and are called feedback casual loops . Feedback causal loops are when a change in one system variable causes a change in another variable that eventually leads to a change in the original variable. The image you see here is a well-know phenomenon currently happening in the Arctic and is related to the carbon cycle. The rising temperature of the Arctic is attributed to rising levels of CO2- a greenhouse gas. Arctic sea ice plays an important role in the temperature of the Arctic. White sea ice reflects solar radiation which has a cooling effect on the climate. Dark ocean water absorbs solar radiation which has a warming effect on the climate.

In pairs or larger group, examine the Arctic causal loop diagram and answer the following questions.

1. What story does this causal feedback loop diagram itell about what is currently happening in the Arctic?

2. Think of rising temperatures as the original element in the Arctic feedback loop. Does melting ice "amplify" or "dampen" rising Arctic temperatures? Why?

3. Why is this feedback drawn as a circle?

4. If CO2 levels continue to increase, how might this affect this feedback causal loop? Why?

Part 2. Using Connection Circles in A Case Study: The Effects of Pine Bark Beetle Infestation on the Carbon Cycle.

As you use the Connection Circle in the case study below, you will find that these "If..then" statements will interconnect in many ways. Lets begin the first of several Connection Circles you will create throughout this module by exploring the effect of a pine bark beetle infestation on the carbon cycle.

Over the past several years, there has been an unusually high Pine Bark Beetle infestation causing a massive die-off of trees. Pine Bark Beetle Infestations have been a part of the natural ecology of western forests for a long time. However, the severity and range of the infestation has been changing. What is going on? What could pine bark beetle infestations have to do with the carbon cycle?

In this activity, you will use the systems thinking tool "Connection Circles" to identify causal connections between the pine bark beetle infestation and three important processes in the carbon cycle:

  1. photosynthesis
  2. decomposition Decomposition is the natural process of dead organisms being rotted or broken down into smaller bits. When soil invertebrates, fungi and bacteria carry out decomposition, they also respire releasing CO2 to the surrounding soil and air.
  3. soil respiration Soil respiration refers to respiration carried out by organisms living in the soil - including bacteria, fungi, worms, beetles etc.

To learn about the pine bark beetle infestation and its severity, view the New York Times slideshow Attacks on a Protective Canopy. Then read the article Climate Change Sends Beetles Into Overdrive! As you read, keep the following questions in mind: What are the important elements of the pine bark beetle infestation story? Using the questions below as a guide, list as many elements as you can.

Materials you will need:
  1. Pencils and colored pencils
  2. A Connections Circle diagram or draw one on your own. Note: larger paper is best.
  3. Access to the Carbon Cycle interactive in Lab 2-B or if unavailable, a hard copy of the carbon cycle image and transcript.
  4. Pine Bark Beetle Infestation story "Element Strips"

Print and neatly cut out.












Setting up your Pine Park Beetle Infestation Connection Circle

(Adapted from The Shape of Life)

1. Draw a large circle on a piece of paper or use a connection circle template.

2. Cut out the "elements of the story" strips and spread them out on the table.

3. Put "Pine Bark Beetle Infestation" at the top outside of the circle.

4. Next, place the "CO2 in the atmosphere increases" and "Warming Atmosphere" strips on opposite sides of "Pine Bark Beetle Infestation"

5. Finally, place the other strips around the outside edge of the remaining circle.

Identifying Causal Connections in your Connections Circle.

Refer to your Carbon Cycle Interactive for help if you need to.

1. Starting at the "Pine Bark Beetle Infestation element" use an arrow to draw your first causal connection. As you draw arrows, think about the casual connections in terms of increases and decreases. Example: If this process increases, then this will cause an (increase or decrease) in another process. Make sure you draw your arrows from the "cause" to the "effect."

2. Continue identifying causal connections until you have drawn at least seven arrows.

Part 3: Identifying feedback loops

Feedback loops (also called causal loops) are everywhere in systems around us. What are feedback loops and why are they important to understanding the impact of the pine bark beetle infestation on the carbon cycle system?

Identifying feedback loops in the carbon cycle allows us to understand why the carbon cycle is behaving a certain way and how it might behave in the future. Feedback loops can often tell us the cause of changes we see in the carbon cycle.

There are two basic types of feedback loops you will be looking for in this activity:

1. Carefully examine the arrows in your Pine Bark Beetle connection circle. Choose one element (for example photosynthesis) and start to look for arrows that "loop back" to your beginning element. This is a feedback loop. For each loop that you find, trace it with a different color marker.

2. Choose one loop and draw it on a separate piece of paper. Indicate whether each arrow leads to an increase (+) or a decrease (-) in the next element. Follow the same process for any other loops you have found on your connection circle.

3. Next, you will identify each loop as either an amplifying feedback loop or a dampening feedback loop.

Hint: There can be both (-) and (+) arrows in a feedback loop, but the last arrow is the most important.

4. Do any of your feedback loops share a common element? If so, try to draw them side by side and connected.


Share your connection circle and feedback loops with other groups or the class.

  • Are the Connection Circles in the classroom all the same? Identify some similarities and some differences.
  • Compare your feedback loops you found in the Pine Bark Beetle Infestation connection circle. Does the feedback loop amplify the initial change or dampen it? What makes you think so?
  • What do the feedback loops tell you about how the Pine Park Beetle Infestation is impacting carbon cycle processes?

Positive and Negative Feedback Loops: The language of scientists.

Scientists who study the carbon cycle have their own terminology for feedback loops. Throughout this module, you will hear scientists refer to feedback loops as either positive or negative. Unfortunately, their choice of terms can be misleading and confusing to non-scientists. We tend to associate positive with "good" and "negative" with bad. However, being "good" or "bad" has little to do with positive and negative feedback loops.

A positive feedback loop A positive feedback creates conditions that amplifies, increases or speeds up a process or variable. Positive feedbacks tend to destabilize a system. is an amplifying feedback. Other words and phrases associated with positive feedback loops are amplifying, vicious circle, snowball effect, domino effect, feeds back in on itself, run-away change, and self-reinforcing loop.

A negative feedback loop A negative feedback loop creates conditions that dampens or slows down a process or variable. Negative feedbacks tend to stabilize or balance a system. is a dampening feedback. Other words and phrases associated with negative feedback loops are dampening, balancing, restores balance, and reducing.

Stop and Think

  1. Re-examine your Pine Bark Beetle feedback loops again. Are they negative or positive feedback loops? How do you know?
  2. Write a statement that describes what happens in the feedback loop(s).


Complex systems such as ecosystems and the carbon cycle have multiple positive and negative feedbacks operating at the same time.

Look at the different causal feedback loops you have identified in your pine bark beetle activity. Hypothesize as to how these feedback loops might differ from each other in terms of their influence on the system, and/or the time scales and spatial scales on which they operate.

Content Extensions:

Articles and videos on pine bark beetles, forests and carbon cycles:

Video: Dr. Susan Prichard and Pine Bark Beetles

Article: The Pine Bark Beetle Blues

Video: Sustainability: Water - Dead Trees and Dirty Water

Feedback loops in other systems: There are many examples of feedback loops (causal loop diagrams) available on the Internet. For example, you might want to explore causal loops in a political system, an economic system, a business system, history or human behavior - the list goes on and on. Research a causal loop that interests you and bring a causal loop diagram to class with a title and brief written explanation. Contribute your causal loops to a feedback wall. Looking at many different examples will help you and your classmates understand feedback loops.

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