What is the focus of this module? The purpose of "Tropical Poison" is to have students address questions of habitat destruction in the Amazon Rainforest and think about biodiversity worldwide.

What will students gain from this module? Students should develop critical-thinking and problem-solving skills appropriate for complex situations. They should come to realize that environmental issues are multi-faceted and that solutions most often involve compromise.

What is the compelling problem that students will face in this module? Students must decide, "Is there a problem?" Students will examine opposing views on the Amazon Rainforest and will take a position on land-use and species conservation in one of the last areas of biodiversity on earth.

What issues will students encounter as they work through this module? Students will encounter a variety of issues related to decision-making and the rainforest, all of which may be explored with remote sensing technology:

• species extinction
• global warming
• deforestation
• water quality
• displacement/extinction of indigenous peoples
• sustained environments in a global economy

What is the role of remote sensing in this module? The Remote Sensing Activities in this module will demonstrate how this technology can increase our ability to make informed decisions about habitat and biodiversity preservation.

Rainforest Remote Sensing Activities
Image processing of the remote sensing images of the Rio Branco area gives students a chance to get some real "hands-on" experience and to come to know the area well. The activities are written assuming the students know some of the basics of image processing (IP): importing files, what a gray-scale image is, etc. For students unfamiliar with IP, there are hot-links within the activities to existing training activities. Herein lies an important trade-off for you, the teacher: using IP involves the students much more deeply in the learning process and gives them "ownership" of the IP products and their results. However, learning IP takes some time. From experience, we find that many students pick up IP quickly, but to learn the skills required in these activities will take several class periods.

Note: Software Requirements: Macintosh users must download NIH Image. (Instructions for Windows users are currently under construction.)

For classes 1) with no access to NIH Image, or 2) insufficient time to learn basic IP, processed images for each of the activities requiring processing are also included in this teacher's section. Using the processed images plus the images in the student module primarily intended for inspection only, students can obtain nearly all of the information relevant to the rainforest module by simply downloading and carefully inspecting the images.

Seeing Environmental Change
From inspection of the full-scale images, the enlarged sections shown on the "Brazil Finder map," and the color composites given below, students should be able to recognize

1. roads (bright line with striaght sections in Area CE)
2. rivers (medium to britht irregularly curving lines in Area C)
3. oxbow lake (medium gray horseshoe-shaped areas in Area CW)
4. ranches (large bright polygonal areas in Area NC)
5. small farms (small irregular bright areas in Area NE)
6. clouds (brilliant blue-white patches in the true color composite), and
7. the jungle itself (green in the 3-2-1 true color composites, red in the 5-3-2 near-IR color composites).

Differences in the apearance of vegetation in Rain Forest 4-5-7 are partially due to the variety of plants and partially due to differences in the availability of water. Note the prominence of stream courses.

Here are some color composites:

First, the true color composite made from Brazil 1-3, 1-2, and 1-1. Notice the deep green of the old forest, the lighter greens and browns of the open fields, the tan of the city, and the blue-white clouds.	Second, the IR composite made from Brazil 1-5, 1-3, and 1-2. Notice the deep red of the forest and the lighter reds and tans of the farms and ranches.

The changes between the 1986 and 1992 images are obvious. The increase in area of the large ranches, the small farms, and the city of Rio Branco is significant. Note the decrease in dark vegetative cover in Area CE. Note also that the cloud patterns are different between the two dates, which can be confusing to students unless they recognize the clouds for what they are. The best way to see the differences is to animate or flicker between Brazil 1-2 and 2-2, or to place them side by side on the computer monitor screen. Another way is to ratio them, in which case an image like this one will be obtained:

In this false-color rendition, the 1986 agricultural areas are colored red and yellow, while the 1992 areas are dark blue. Note that the same color scheme applies to the 1986 and 1992 clouds. Notice that the farms and ranches have been built outward from the roads and pre-existing open areas so that farmers could avoid the difficulty of traveling through virgin rainforest. One can assume that the greatest growth in the near future will be outward from the existing open areas.

The increase in agricultural area between the two images can be measured fairly easily using the density slice command as described in the student section. The two images below show how Brazil 1-2 and 2-2 will appear with the appropriate density slice applied.

Each image has pixels highlighted in red and squares outlined in green and blue. The location of the squares is the same (to the pixel) in each image. The sizes of the squares were chosen to make calculation of the areas simple. The Analyze/Measure command will calculate the area of the highlighted (red) pixels within the selected square. The results from measurement on these squares are;

The difference in percent areas between the blue square and the green square in the same image is simply due to each square's size and location. Obviously the percentages are not exact. Students should get similar values unless they choose small squares centered on Rio Branco or in the middle of the rain forest. Students should be encouraged to pick a square representative of the whole image (ignoring the clouds). Note that the red pixels in the middle of the forest at lower left in each image are due to lighting changes across the image, not to farms.

As seen from the measurements in the table above, the increase in area of the developed lands is about a factor of 2 in just 6 years. While this may seem unrealistically large, this increase can be compared with increases in other areas in Brazil given in the Brazil Remote Sensing web site. The changes can also be compared with the increase in population of Rio Branco and the state of Acre of which Rio Branco is the capital:

Finally, the sizes of Brazilian ranches and farms can be compared with the sizes of American farms and ranches using:

Preparation Checklist--have you thought of everything?

Providing for Reflection
Despite a limited level of commitment while working on a module, students can still experience significant learning if they enter into the reflection process. Ideally, reflection occurs at various points during the module; however, reflection done only at the close of a module can also be a powerful learning experience.