The Carbon Cycle and Quantifying the Carbon Cycle
Scientists working on the Bringing Wetlands to Market project will quantify the carbon stored
in a temperate coastal salt marsh and the movement, or flux, of gases and organic material
into and out of the system. They are studying whether wetlands are especially effective at
taking up and storing, or sequestering, carbon. This exercise provides a review of how carbon
cycles in the environment and how much carbon is in different parts of the cycle.
The Carbon Cycle
Teachers may choose to use a short reading "Carbon Cycle Background" or a longer reading
"Carbon Cycle Background UNH" depending on the time available. Here is a link to the
diagram of the carbon cycle that is included as a student page below.
1. Have students read the background article on the carbon cycle. Have them answer these
questions in writing or discuss orally:
a. What is the role of plants in the carbon cycle?
b. Describe the process plants use to take CO2 from the air and assemble
carbohydrate molecules to store energy. (see “Lego Photosynthesis Lesson” for
visuals and ideas)
c. How is the carbon cycle related to climate change?
2. Examine the Global carbon cycle diagram (included below)
The numbers are enormous and the labels may be unfamiliar, so here is a conversion guide:
1 Petagram (Pg) = 1015 g (one quadrillion grams)
1 Petagram (Pg) = 1012 kg (one trillion kilograms) = 2.2 trillion pounds
1 Petagram (Pg) = 109 mt (one billion metric tonnes) = 1.1 billion tons
Have students write or discuss the answers to these questions:
a. What are the main reservoirs (pools) of carbon and where does carbon move to
from each reservoir?
b. What is one exchange of carbon that happens relatively quickly?
c. What parts of the carbon cycle experience change very slowly?
d. What is the significance of carbon sinks (reservoirs) in relation to climate change?
e. How does fossil fuel combustion affect the carbon cycle?
f. What could be done to help increase natural carbon sinks?
Quantifying the carbon cycle
1. Ask students to examine the diagram of the carbon cycle and the exchange among the
pools or reservoirs.
2. Have them fill in the table with the major sources and sinks (reservoirs). These are
labeled in blue on the diagram. (include surface ocean and deep ocean separately) Fill
in the volume of C in each and the annual flux or exchange. One example is provided. A
source can have more than one sink.
3. Have students keep track of questions that arise during this exercise. Share some of
the questions and discuss how students could find the answers.
The numbers are enormous and the labels may be unfamiliar, so here is a conversion guide:
1 Petagram (Pg) = 1015 g (one quadrillion grams)
1 Petagram (Pg) = 1012 kg (one trillion kilograms) = 2.2 trillion pounds
1 Petagram (Pg) = 109 mt (one billion metric tonnes) = 1.1 billion tons
1 petagram = 1quadrillion grams of carbon, or 1.1 billion tons of carbon
Where is the Carbon? Where does it go?
Name of source or sink
(reservoir)
Volume in storage
Amount of annual flux (flux
Where does it go?
Soil
1,500 Pg
58 Pg
Atmosphere
means flow or movement to
another reservoir)