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How Things Change


Study the environmental history of the Rio Grande valley to compare the past to the present and identify factors that have changed it.


Students will recognize that the environment in the Rio Grande valley has drastically changed in the past 400 years. They will be more aware of the impact of their every day decisions on our environment.


Students will:

  1. Identify at least three factors that caused an environmental change in the Rio Grande valley in the past 400 years
    1. Identify a change that occurred due to each factor.
    2. Specify how that factor contributed to the change.
  2. Describe how factors interact to cause various levels of change.
  1. Guided Imagery
    1. Have students close their eyes and envision the place you describe.
    2. Read the text of "River Valley #1" (below).
    3. Have students draw the scene as they imagined it.
  2. Identification of area
    1. Working in groups, students should study maps and atlases of North America to identify a place they think could be the place you have just described.
    2. Students should defend their choices based on phrases they remember (e.g. being warm and sunny or having grasslands and wetlands)
    3. Read the Desert Diary entry from January 30, 2001 (below).
  3. Identification of changes to the environment
    1. Have students identify the man-made changes described in the story.
    2. Create lists of some of the things humans have done and their impact on the environment.
    3. Students work in groups to identify other changes and their impact on the environment.
    4. Each group should focus on three changes.
  4. Changes posters
    1. Groups create sets of posters depicting the area 400 years ago, the area after one of their chosen changes, after two, and after all three.
      1. Students identify the human action and the resulting changes in each poster.
    2. Groups present their posters to the class. They describe not only each change, but how one change interacts with others.
  5. Discussion
    1. Go back to the list of changes and ask if there are other things to add.
    2. Students identify how one change might affect others.
    3. Students identify how their actions can also affect the changes that have already happened.
    4. What are the pros and cons of each of the changes.
  6. Journal entries
    1. Each student writes about how his or her actions affect the environment.
    2. Students suggest what might happen in the future, either with or without other human changes (changes can have positive or negative impact).


Examine the validity of the changes and their impacts depicted in the posters

Check journal entries for thoughtful analysis of the studentís current lifestyle, specifically on how it might affect the environment.




1. Students create classroom mural showing many changes and their impacts, including how one can affect another.

2. Students write journal entries that might have been made by the Rio Grande over time (see "A Riverís Tale" lesson)

River Valley #1

Imagine a clear river, teeming with fish, meandering through a beautiful wooded valley with great stands of majestic cottonwood trees and thickets of willows. Marshes and the river support flocks of birds almost without end. As the river has meandered, it has left numerous oxbow-wetlands. Annual floods provide water vital for the seeds of cottonwood to germinate. The grass is as tall as a person wandering through, and travelers tarry to enjoy the bounty. The climate is warm and almost perpetually sunny. There is more than enough food to support a wide variety of animals and humans alike. Many people travel through the area, and they invariably stop, after having traversed difficult terrain to reach this oasis.

January 30, 2001, Desert Diary

Imagine the Rio Grande as a clear river, teeming with fish, meandering through a beautiful wooded valley with great stands of majestic cottonwood trees and thickets of willows. Marshes and the river support flocks of birds almost without end. No wonder the conquistadors tarried to enjoy the bounty. The climate has changed little during the 400 years since then--today's far different valley is primarily due to OUR influence.

We've cleared the bottomlands, filled in the oxbow-wetlands, straightened the river to conserve irrigation water, and turned the Rio Grande into a canal with cement banks through urban areas to stop its meandering. We've built dams upstream for water storage and to prevent flooding, without which few cottonwoods can sprout.

In trying to tame the area, we've destroyed much of what the conquistadors encountered. As always in fragile desert regions, the major problem is to serve human needs without destroying much of what makes life worth living.

For Texas Teachers

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