Analyze an environmental problem doing calculations

Carbon in a logged forest

Units 1, 5 and 9
10 points
About 24 minutes

You can use a calculator on this question, just like on exam day.

You work through an environmental scenario using numbers: set up and solve calculations (showing your work), then explain the science and propose solutions. Several of the 10 points come from the calculations, usually one for the setup and one for the answer. On the exam: Question 3 of 3 in the 70-minute free-response section (Section II is 40% of the exam score).

The question

A timber company plans to clearcut 150 hectares (ha) of an old forest. The trees store an average of 180 metric tons of carbon per hectare. Each metric ton of carbon that ends up in the atmosphere forms 3.67 metric tons of carbon dioxide (CO₂).

Suggested time: 24 minutes

Your answers are saved in this browser as you type.

Part (a)

2 points

Calculate the mass of carbon, in metric tons, stored in the trees on the 150 ha to be cut. Show your work.

Your answer to part (a)

0 / 2,500 characters

Part (b)

2 points

After the trees are cut, 60% of the carbon they stored is released to the atmosphere within 20 years as the branches, roots and leaves decay or are burned. The rest stays in wood products. Calculate the mass of CO₂, in metric tons, released from the cut trees. Show your work.

Your answer to part (b)

0 / 2,500 characters

Part (c)

2 points

The company replants the 150 ha. The young forest will take up an average of 2.5 metric tons of carbon per hectare per year. Calculate the number of years it will take the new forest to take up the same amount of carbon that was released in part (b). Show your work.

Your answer to part (c)

0 / 2,500 characters

Part (d)

1 point

Explain how clearcutting the forest can increase soil erosion.

Your answer to part (d)

0 / 2,500 characters

Part (e)

1 point

Describe one way the clearcut could harm fish in a stream that flows through the logged area.

Your answer to part (e)

0 / 2,500 characters

Part (f)

1 point

Propose one sustainable forestry practice that the company could use instead of clearcutting.

Your answer to part (f)

0 / 2,500 characters

Part (g)

1 point

Explain one way that cutting the forest affects the amount of CO₂ in the atmosphere, other than by releasing the carbon stored in the cut trees.

Your answer to part (g)

0 / 2,500 characters

Checking scoring…

Scoring it yourself shows you the rubric, examples and a model answer. Try writing your answer first.