Week 11: Using Satellite Data to Investigate Deforestation

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Using ImageJ to Detect Change

amazon_deforestation_2009 Clearing of the Amazon rainforest in Rondonia in August of 2009.

Investigation questions:

  • How has deforestation in the Amazon rainforest changed over time?
  • What is the pattern of deforestation? Which areas were cleared first, later, and most recently?

One of the most deforested parts of the Amazon rainforest lies within the state of Rondonia in Brazil. The loss of the rainforest is primarily due to human activities such as raising crops and livestock. Unfortunately, although these activities have short-term benefits to people, over time, the loss of the rainforest can lead to the extinction of plants and animals as well as contribute to global climate change.

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Download Images of Deforestation

Download three images of deforestation to your Week 11 folder or directory. These images show deforestation in the Amazon rainforest during the years 2001, 2005, and 2009.

  1. Click the thumbnail image below to open a full-size version in a separate window. Then right-click (Win) or control-click (Mac) the full-size image to choose File > Save Image As... and save it to your Week 11 folder. Close the image window after you have downloaded its file.
  • amazon_deforestation_2001 amazon_deforestation_2001.jpg
  • Repeat the procedure for the 2005 image.
    • amazon_deforestation_2005 amazon_deforestation_2005.jpg
  • Then repeat the procedure once more for the 2009 image.
    • amazon_deforestation_2009 amazon_deforestation_2009.jpg

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    Launch ImageJ and Import the Images as a Stack

    • Launch ImageJ by double-clicking its icon ImageJ Icon Small on your desktop or by clicking its icon in the dock (Mac) or Launch Bar (Win).
    • Import the three images into ImageJ as a stack.
    1. Choose File > Import > Image Sequence...
      file import image 1
    2. Navigate to the folder where you stored the images and select the first one.
      file import image 2
    3. In the Sequence Options window that opens, set the Number of Images to 3, the Starting Image to 1, Increment by 1, do not scale the images, and make sure Sort Names Numerically is checked. Then click OK.
      file import image3

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    Animate and Explore the Stack to Observe Change Over Time

    You can step through a stack one slice at a time, or you can animate it like a repeating movie loop.

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    Process the Stack for Analysis

    1. Choose Process > Binary > Make Binary.
      process stack make binary
    2. The Convert to Mask window opens. Make sure the Calculate Threshold for Each Image and Black Background boxes are checked. Then click OK.
      convert to mask dialog
    3. This is what the stack looks like when converted to binary format. The cleared areas are white, while the forested areas are black.
      process stack make binary results
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      Measure the Area of Deforestation Each Year

    1. Choose Image > Adjust > Threshold.
      image adjust threshold
    2. When the Threshold window opens, be sure that Dark background is checked. Adjust the threshold as needed so that all the white pixels are highlighted in red. When you are finished, do not click apply. Just close the threshold window.
      image adjust threshold dark background
    3. Select the measurements that will be recorded in the Results window.
    4. Measure the area of deforestation on each slice of the stack (all three images).
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      Create an RGB Color Image from the Stack

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    Interpret Results

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