EarthLabs > Climate and the Carbon Cycle: Unit Overview > Lab 4: Forests - Changes in the Land > 4A: Forests: Wildfires and Deforestation

Forests: Changes in the Land

Part A: Forests: Wildfires and Deforestation

Discussion

Why care about forests and the carbon cycle? With your partner, group or class, list as many reasons as you can.

Forests have been sequestering carbon for millennia, but how? Remember when you were asked to consider how Giant Sequoia Trees could grow so tall? If you don't have the answer to these questions by now, view the video, Forest carbon 101, produced by The Nature Conservancy. As you watch the video, think about this fact: up to one-fifth of global carbon emissions are caused by forest deforestation and degradation.
If an average healthy tree absorbs about 13 pounds of carbon per year, imagine how much carbon an entire forest can absorb! But, what happens to the carbon in that forest if many of its trees are cut down to make way for agriculture, farms, cattle ranches, and housing developments? To find out where deforestation is happening in the world, examine the Deforestation Hot Spot Map on the right. Take some time to explore the map and then answer the Checking In questions below.

Checking In

Check your understanding of the map graphic above by using the questions below. Select all the answers that are correct, and then click the Check Answers button at the bottom of the list.

  1. Which of the following countries/areas of the world are seeing increased deforestation?
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    [INCORRECT]
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  2. Which countries/areas of the world are adding forests?
    [INCORRECT]
    [INCORRECT]
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  3. Which countries have forests that are carbon sinks?
    [INCORRECT]
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In this next section you will consider forests in Latin America and the Amazon.

Trouble in the Amazon?

When you analyzed the "Deforestation Hot Spot" map above, you observed that tropical forests in Indonesia, Latin America, and Africa are hot spots for deforestation. How much carbon would be lost in the deforestation of the Amazon Rainforest? To answer that question, consider the new NASA map of Carbon Storage in Tropical Forests, on the right. This map uses satellite and ground measurements to quantify the amount of carbon stored in tropical forest biomass. Remember that a tree's biomass includes all the carbon compounds in the tree's leaves, branches, trunk and roots. Data shows that tropical forests contain 247 billion tons of carbon. Almost half of this 247 billion tons of carbon is stored in Latin American forests.

Because the Amazon forest is so large and so much carbon is stored there, deforestation in this region concerns us all. The larger the forest, the greater its impact on the carbon cycle. What impact will deforestation have on the Amazon Rainforest and its ability to remain a strong carbon sink? To help you answer this question, read a NASA article on deforestation in Rondônia, Brazil. Then, use the interactive timeline at the beginning of the article to view changes in forest cover from 2000 to 2010 taken by NASA's MODIS.


Checking In

  • By 2003, how many square kilometers had been cleared from the Amazonian Forest in Rondônia? How many acres would that be? Use the metric conversion website to help you answer that question.
    67,764 sq kilometers = 16,744,849 acres.

  • One acre of forests can absorb approximately one ton of carbon dioxide from the atmosphere each year. If deforestation has cleared 16,744,609 acres in just Rondônia, how many less tons of atmospheric carbon dioxide will be stored in the trees every year?
    16,744,609 tons of carbon dioxide

Stop and Think

1. Describe how deforestation can impact the the amount of carbon dioxide in the atmosphere.

Up in Smoke: Fire and the Carbon Cycle.

Slash and Burn Farming.

Cutting down trees is only one part of a complex "carbon cycle" story in the Amazon rainforest. When rainforest trees are cut, burned, or left to decompose, what happens to the carbon contained in those trees? What happens to the land left behind? Answers to this last question are dependent on the local economy and the needs of small communities to provide for their families. Small farmers and ranchers use a very old technique called "slash and burn" to clear and prepare the land for agriculture and cattle. In slash-and-burn agriculture, farmers will typically cut forests months ahead of the dry season. During the dry season, the "slashed" trees dry out and are then burned. The ash from the burned trees fertilizes the soil to support crops such as as rice, corn and soybeans and grass for cattle. Unfortunately, the nutrients in the soil are used up fairly quickly, the land becomes barren and farmers move on to slash-and-burn other parts of the rainforest. In this way, fire and soil become part of this complex carbon cycle, the economy of the rainforest and the people who live there. So, what can be done to mitigate the impact of slash and burn farming on the carbon cycle? Read about the work of Mike Hand, a British ecologist, and Inga trees to find out!

Mike Hand, a British ecologist, has lived in and studied the rainforests in Honduras for over twenty years. He observed that slash and burn was creating a vicious cycle that destroyed forests in order to create agricultural land that could be farmed only temporarily. Eventually, the land turned into a nutrient-deficient barren wasteland, farmers grew poorer and poorer and even more rainforest was cut down. Mike's ideas and efforts on stopping this vicious cycle of "slash and burn" have recently been portrayed in an award winning documentary Up in Smoke. If the full documentary is unavailable to watch, you can watch five video clips created by Oxfam from the documentary here. Then, work with a partner or a group to complete the task below.

The Task: Watch the five Oxfam short videos, or the documentary, linked above. As you watch, take notes that will allow you to compare and contrast the "slash and burn" farming with sustainable "crop alley" farming in terms of:

Use your notes to create a diagram, poster or a story that describes how the carbon cycle differs when "slash and burn" methods are used versus sustainable "crop alley" methods. Describe as many changes to the carbon cycle that are part of this story.

Stop and Think

2. Think about the complex story of deforestation, slash and burn agriculture and the carbon cycle in the Central American and Amazon rainforests. Describe how deforestation, combustion and decomposition all impact the amount of carbon dioxide in the atmosphere.

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