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:

  • How has the Tamarix plant's invasion proceeded over time?
  • What are the factors limiting Tamarix's spread through the entire United States?
  • How are scientists using Satellite imagery to aid in predicting Tamarix's next move?





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
  • Launch My World by double-clicking its icon on your desktop or by clicking its icon in the dock (Mac) or Launch Bar (Win).
  • Choose File > Open, navigate to .../My World/data/Invasive_SpeciesMW and select the file inv_spc.m3vz. Then click Open.
  • Once the map opens, turn on the U.S. Rivers and Tamarix layers.
  • Switch to Visualize mode. Use the Zoom In tool to click and drag a box, around the contiguous United States.
    1. Turn on the U.S. Rivers and Tamarix layers by clicking in the checkbox next to their names.
      1 tamarix US rivers on
    2. Use the Zoom In tool to click and drag a box, around the contiguous United States.
      2 tamarix US rivers zoomed in
  • Make Tamarix the active layer and zoom to its extent. The map will now be focused on the Western United States where the Tamarix invasion began.
  • Make Tamarix the active layer by clicking its name. Click the Zoom to Active Layer tool zoom to active layer to zoom to the extent of the Tamarix layer. The map will now be focused on the Western United States where the Tamarix invasion began.
    3 zoomed to Tamarix

  • Turn on the U.S. States layer.
  • 4 US states layer on
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Investigate the Tamarix Invasion in the United States

Where is the present Tamarix invasion and how far has it spread across the United States?
  • Make Tamarix the active layer by clicking its name.
  • Click once on the Lasso lasso tool tool in the toolbar.
    1. On the map, click and drag to draw a circle around a group of Southwestern states.
    2. Accept the default name for the selection. "Lasso Selection 1".
    3. When the tool is released the selected Tamarix points are highlighted yellow. These points are selected because Tamarix is the active layer.
    1. Click once on the Lasso lasso tool tool in the toolbar.
    2. On the map, click and drag to draw a circle around a group of Southwestern states.
    3. Accept the default name for the selection. "Lasso Selection 1".

    4. 5a accept name
    5. When the tool is released the selected Tamarix points are highlighted yellow. These points are selected because Tamarix is the active layer.

    6. 5b laso selection complete
    6 delete selection menu
  • Clear the selections by clicking on the Delete Selection button in the toolbar above the Layer list.
  • Change the active layer to U.S. Rivers and repeat the selection process.
  • How do the results differ?
    U.S. Rivers are selected on this map.
    7 rivers slected with lasso
    Tamarix points are selected on this map.
    5b laso selection complete
  • Clear the selections by clicking on the Delete Selections button at the top of the Layer list.
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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.

  • Turn on and activate the AZ Rivers with Names layer.
  • Use the Zoom to extent of the active layer zoom to active layer tool to zoom into the state of Arizona and the rivers.

  • 14 zoom into AZ rivers with names
  • Click on the AZ Rivers with Names layer with the Identify tool identify to learn the names of the rivers in Arizona which are invaded by Tamarix.
  • In the identify results window, scroll across to find the field "Name".
    1. With the AZ Rivers with Names layer active, click on an AZ River with the identify tool identify .
    2. In the identify results box, scroll across to find the field "Name". The map and results window.
      15 use identify tool results
  • List several rivers that have been invaded by Tamarix.
    Arizona rivers that have been invaded include the Colorado, Salt, Verde, Santa Maria, Bill Williams and many others.
  • Other Tamarix invasions do not appear to be in streams. Since Tamarix needs wet conditions to survive its first year, what types of areas might also be suitable habitat for Tamarix?
    Answer: Wet areas such as wetlands or marshes are also suitable habitat.
  • Turn off the Identify tool, by clicking on the Pointer tool. The red marquee around the Identify tool should be turned off.
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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.

  • Turn off the U.S. States, Countries and AZ Rivers layers.
  • Turn on the vegetation index image file NDVI_6.1.09.TIFF.
    This file, named NDVI_6.1.09.TIFF, shows where the vegetation has "greened up" with spring vegetation. It is a geospatially calibrated image file, or GEO TIFF, from June 6th, 2009. It was downloaded from NASA NEO.
  • Make Tamarix the active layer.
  • One the NDVI file has loaded in My World, choose Zoom to Active Layer in this case, Tamarix points.
  • If necessary, adjust the layers so that the NDVI_6.1.09.TIFF, image is below the Tamarix layer.
  • Zoom and Pan to compare the location of the Tamarix points to the green regions of the image. Areas with healthy vegetation are prime locations for new invasions of Tamarix.
  • From NASA NEO

    The colors on these maps show a measure of the "greenness" of Earth's landscapes. The values on these maps – ranging from -0.1 to 0.9 – have no unit. Rather, they are index values in which higher values (0.4 to 0.9) show lands covered by green, leafy vegetation and lower values (0 to 0.4) show lands where there is little or no vegetation.


    NDVI legend Legend of NDVI Image

    As can be seen through a prism, many different wavelengths make up the spectrum of sunlight. When sunlight shines on objects, certain wavelengths are absorbed and other wavelengths are reflected. The pigment in plant leaves – chlorophyll – strongly absorbs visible light for use in photosynthesis. The cell structure of the leaves, on the other hand, strongly reflects near-infrared light. The more leaves a plant has, the more these wavelengths of light are affected. Scientists exploit this knowledge of plants' interactions with light to map the density of green vegetation across Earth's landscapes by designing satellite sensors to measure the wavelengths of red and near-infrared light that is absorbed and reflected by plants all over the world.

    Subtracting plants' reflectance of red light from near-infrared light and then dividing that difference by the addition of the red and near-infrared light reflected produces a resulting value that scientists call Normalized Difference Vegetation Index (NDVI). The NDVI maps shown here were made using data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA's Terra satellite.

    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.

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?

  • Turn on the elevation Elevation above 2000m layer. Zoom to the full extent of this layer.
  • Use the zoom and pan tools to look at the map. Are there many Tamarix sightings at elevations above 2 km? What climate conditions change at this elevation?
  • Generally no, there are very few Tamarix plants at elevations above 2 km or 6600ft. At this elevation in the Western United States it is much colder and drier.
  • Turn on the U.S. Rivers layer on and off as needed and /or move the U.S. Rivers layer above the Elevation layer.
  • Map with Elevation above 2000m layer added.
    17 zoomed to eevationbaove 2000m
  • Based on the data in the Satellite NDVI image, Elevation above 2000m, and the U.S. Rivers layers, predict the direction that you think will Tamarix move in the next few years in the USA.

  • Use the Identify identify tool, your selection skills and the layers in the project to answer the following questions;
    1. Which U.S. Rivers seem to be the most likely to be invaded?
    2. With the U.S. Rivers layer active, use the identify tool to identify the name of the US River, you think is likely to be invaded by Tamarix. In this case, the Snake River has been identified.
      18 snake identified
    3. Where would you send your land management team next?
    4. The Tamarix invasion is most likely to move into Western states like Idaho and Washington. It will also move eastward into the Midwest. It prefers to follow river corridors.
    5. What factors could be limiting the spread of Tamarix?
    6. The invasion is limited by moist soils, temperature and water availability. There are no natural predators to Tamarix.
  • Quit My World. Do not save your work.
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Resources


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