Eyes in the Sky II > GIT Web Course > Module 2 > Week 5 > Using GIS to Analyze and Predict Invasions > Using My World to Analyze and Predict Invasions

Week 5: Monitoring Invasive Species

Using My World to Analyze and Predict Invasions

Tamarix forest in riparian zone. Image courtesy of Steve Dewey, Utah State University, United States.
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Key Investigation Questions:






Introduction

Tamarix, or saltcedar, grows as a woody shrub or small tree. It was introduced to the United States in the 1850's as an ornamental plant capable of erosion control. It successfully adapted and quickly spread into wetlands displacing native trees such as cottonwood, willow and mesquite. Now, Tamarix has invaded nearly all the watercourses and wetlands in the Southwest US. As one of the most successful and common invasive species in the United States, it has overtaken nearly one million acres of habitat. Since it can transpire as much as 300 gallons of water per day, it is capable of causing a wetland to completely dry up. Additionally, Tamarix has a tendency to increase the salinity of the soils in which it grows and it is of little or no value to wildlife. Although Tamarix is difficult to eradicate, in locations where it has been eliminated native vegetation and wildlife have returned and flourished.

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Launch My World and Orient the Map for the Investigation

My World Icon top of page

Investigate the Tamarix Invasion in the United States

Where is the present Tamarix invasion and how far has it spread across the United States? top of page

Where is the Tamarix invasion the most severe?

Tamarix can be found throughout the Southwest United States. Some states have more of a Tamarix problem than others, but because Tamarix spreads easily and is very difficult to eradicate, plant biologists are keeping a close eye on the situation.

Zoom In and Pan pan tool around the map to get a better idea of the extent of the invasion and to answer the following questions.

  1. In which states has Tamarix been sighted?
    Tamarix has been sighted in the following states:
    • California,
    • Oregon,
    • Idaho,
    • Montana,
    • Wyoming,
    • Nebraska,
    • Kansas,
    • Oklahoma,
    • Texas,
    • New Mexico,
    • Arizona,
    • Utah,
    • Colorado.

  2. What relationship do you see between rivers and Tamarix?
    In general, Tamarix follows rivers.
    Note: The U.S. Rivers layer in My World does not contain all rivers in the United States. So although you see Tamarix in parts of Nevada and California, the map is not displaying the invaded river.
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Create a Spatial Query to Investigate the Extent of the Invasion

Use the Lasso tool to select Southwest states to investigate the extent of the invasion

Make U.S. States the Active layer and zoom in and select Arizona with the Lasso selection tool.

  1. Make U.S. States the Active layer.
  2. Click and hold on the Lasso lasso tool tool.
  3. Click inside the state boundary of Arizona.
  4. Release the lasso selection tool, name your selection "Arizona". Arizona (AZ) should now be highlighted on the map. If you get several states, try again. Hint: You might need to zoom into the states to get more accurate results.
    1. Make U.S. States the Active layer by clicking its name.
    2. Click and hold on the Lasso tool.
    3. Click just inside the state boundary of Arizona.
      8 lasso tool selecting az
    4. Release the selection tool, name your selection "Arizona". Arizona (AZ) should now be highlighted. If you get several states, try again. Hint: You might need to zoom into the states to get more accurate results.
      10 AZ is selected
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Use the Analyze mode to select the records from the Tamarix database that are completely contained within the boundaries of the state of Arizona. This is a type of spatial query that is called "containment".

select by spatial relationship Select ... by Spatial Relationship... By Containment.
  1. In Analyze mode, Select ... by Spatial Relationship... By Containment.
  2. Find records from Tamarix that Are Completely Contained By Records in Arizona. Click OK Name the result Arizona Tamarix.
  3. Once the selection has been made, change the Highlight mode of U.S. States to Transparent Unselected. This change will make the selected points stand out against the Arizona selection.
  1. In Analyze mode, Select ... by Spatial Relationship... By Containment..
  2. Find records from Tamarix that Are Completely Contained By Records in Arizona. Click OK Accept the default name.
  3. Once the selection has been made, change the Highlight mode of U.S. States to Transparent Unselected. This change will make the selected points stand out against the Arizona selection.
    10 transparent unselected

Discover the results of the selection

  1. Return to the map and make Tamarix the active layer.
  2. Open the Table of Layer of Tamarix.
  3. How many results are have been selected?
    1. Open the attribute table of the selection of Tamarix.
      11 show table of selected
      3333 Tamarix are recorded within the state of Arizona.
      12 show table of selected

Repeat this entire process with several other Southwestern States to find the next most invaded state.

Tamarix Records:
AZ - 3333 records
NM - 422 records
UT - 326 records

Clear the selections by clicking on the Delete Selections. button.

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Focus on Arizona Tamarix

As you just discovered, Arizona's Tamarix invasion is the severe. Now, you'll investigate the specific Arizona rivers that have been invaded by Tamarix.

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Add Satellite Data to Connect Tamarix Spread with Vegetation Index

By using the satellite data of vegetation health the scientists at NASA and USGS are able to use habitat preferences, such as moist soils and low elevations, to begin to predict where Tamarix plants were most likely to appear in the future.

Adjust the layers on the map for the investigation.

Plants are sensitive to their environment and so they serve as a good indicator whenever there is change. Scientists routinely produce global NDVI maps to help them monitor and investigate shifts in plant growth patterns that occur in response to climate changes, environmental changes, and changes caused by humans. Farmers and resource managers also use NDVI maps to help them monitor the health of our forests and croplands. So these maps are useful both for scientific research as well as societal benefit.

Notice that the in Arizona the Tamarix Invasion prefers the lower elevations where there is more desert. It is found in the river corridors and other low lying wet areas.

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Add Elevation to the Map to Solve the Puzzle

So far we have observed that Tamarix invasion patterns follow the river corridors and also other areas that appear to have healthy green vegetation in the satellite NDVI image. So, why doesn't Tamarix invade everywhere? What is the missing element in the puzzle?

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Resources


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