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

Week 5: Monitoring Invasive Species

Using ArcGIS 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 ArcGIS and Orient the Map for the Investigation

Shortcut1
  • Launch ArcGIS by double-clicking its icon on your desktop or by clicking its icon on the Launch Bar (Win).
  • Choose File > Open, navigate to (path) and select the file C:/EYESINTHESKY2/WEEK5/Invasive_SpeciesAM. Then click open.
  • Once the map opens, turn on the US Rivers and Tamarix layers. Use the Zoom In Zoom In tool to click and drag a box, around the contiguous United States.
    1. Turn on the US Rivers and Tamarix layers by clicking in the checkbox next to their names.
      1 US  Rivers Tamarisk Layers
    2. Use the Zoom in tool to click and drag a box, around the contiguous United States. 2 Contiguous States
  • Right click on the Tamarix layer and click on Zoom To Layer. The map will now be focused on the Western United States where the Tamarix invasion began.
  • Right click the Tamarix layer and click on Zoom To Layer in the popup context box. The map will now be focused on the Western United States where the Tamarix invasion began.
    3 Tamarisk Invasion

  • Turn on the US States layer.
  • 4 US States Layer
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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?
  • Right click on the Tamarix layer, click on Selection, and then click on Make This The Only Selectable Layer.
    5 Tamarisk Only Selectable Layers
  • Click once on the Select Feature Select Feature Tool tool in the toolbar.
    1. On the map, click and drag to draw a rectangle around a group of Southwestern states.
    2. When the tool is released, the selected Tamarix points are highlighted in blue. These points are selected because you chose the Tamarix layer as being the only selectable layer.
    1. Click once on the Select Feature Select Feature Tool tool in the toolbar.
    2. On the map, click and drag to draw a rectangle around a group of Southwestern states.
      6 Select US States
    3. When the tool is released, the selected Tamarix points are highlighted blue. These points are selected because you chose the Tamarix layer as being the only selectable layer.
      7 Selected Tamarisk Points
  • Clear the selections by clicking on the Clear Selected Features Clear Selected Feature button
  • Right click on the US Rivers layer and repeat the selection process starting with making US Rivers the only selectable layer.
  • How do the results differ?
    US Rivers are selected on this map.
    8 Select US Rivers
    Tamarix points are selected on this map.
    7 Selected Tamarisk Points
  • Clear the selections by clicking on the Clear Selected Features Clear Selected Feature button
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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 and Pan 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?
  3. In general, Tamarix follows rivers.
    Note: The US Rivers layer in AEJEE 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

Query Southwest states to investigate the extent of the invasion.

  1. Right click on the US States layer, click on Selection, and then click on Make This The Only Selectable Layer.
    9 US State Selectable Layer
  2. Click on the Select Feature Select Feature Tool tool.
  3. Click inside the state boundary of Arizona.
  4. After clicking inside the Arizona state boundary, Arizona (AZ) should now be highlighted (outlined in blue).
    1. Right click on the US States layer, click on Selection, and then click on Make This The Only Selectable Layer.
    2. Click on the Select Feature Select Feature Tool tool.
    3. Click inside the state boundary of Arizona.
    4. After clicking inside the Arizona state boundary, Arizona (AZ) should now be highlighted (outlined in blue).
    5. 10 AZ Selected
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Use the Selection, Select By Location menu option to select the records from the Tamarix database that are contained within the boundaries of the state of Arizona. This is a type of spatial query called "containment".

  1. Click on the Selection menu option at the top of the map view. A pulldown context menu will open.
    11 Selection by Location
  2. Click on Select by Location.
  3. In the Select By Location dialog box, set the "I want to:" pulldown arrow to "select features from."
  4. In "the following layer(s):" Place a checkmark in the box in front of Tamarix.
  5. Set the "that:" pull down arrow to "are within."
  6. Set "the features in this layer:" to US States.
  7. 12 Select by Location Context
  8. Click OK. The buffer dialog window will be displayed on the map.
    1. Click on the Selection menu option at the top of the map view. A pulldown context menu will open.
      11 Selection by Location
    2. Click on Select by Location.
    3. Set the "I want to:" pulldown arrow to "select features from."
    4. In "the following layer(s):" Place a checkmark in the box in front of Tamarix.
    5. Set the "that:" pull down arrow to "are within."
    6. Set "the features in this layer:" to US States.
    7. 12 Select by Location Context
    8. Click OK. The Select By Location dialog window results will be displayed on the map.
    13 Tamarisk Selected Points in Blue

Discover the results of the selection

  1. Return to the map and right click the Tamarix layer.
  2. Open the Attribute Table of Tamarix.
  3. How many results have been selected?
    Right click to open the Attribute Table of the Tamarix layer.
    14 Attribute Table
    3333 Tamarix are recorded within the state of Arizona.
    15 Attribute Table with Selection

Close the Tamarisk Attribute Table by clicking on the "X" on the top right corner of the table (hint, do not click on the "X" at the very top of your screen as that will close your project.)


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 Clear Selected Features Clear Selected Feature button

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Focus on Arizona Tamarix

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

  • Turn on the AZ Rivers layer.
  • Right click on the AZ Rivers layer and click on Zoom to layer to zoom into the state of Arizona.
  • Click on the AZ Rivers layer with the Identify tool Identify to learn the names of the rivers in Arizona which are invaded by Tamarix.
  • In the Identifyresults box, scroll down to find the field "Name".
    1. Right click on the AZ River layer with the Identify tool Identify .
    2. Identify Pull down
    3. In the Identify results box, scroll down to find the field "Name".

    4. 17 Arizona River Name in Identify
      The map and results window.
      18 Map Identify 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.
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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 US States, Countries and AZ Rivers layers.
  • Collapse the US States layer.
  • 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.
  • Right click on the Tamarix layer and choose Zoom to Layer.
  • 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.

    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 > 2km layer. Zoom To 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 the US Rivers layer on and off as needed and /or move the US Rivers layer above the Elevation layer.
  • Map with Elevation > 2 km layer added.
    20 NDVI and Elevation
  • Based on the data in the Satellite NDVI image, Elevation > 2km, and the US Rivers layers, predict the direction that you think Tamarix will move in the next few years in the United States.

  • Use the Identify Identify tool, your selection skills and the layers in the project to answer the following questions;
    1. Which US Rivers seem to be the most likely to be invaded?
    2. With the US Rivers layer on, 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.
      21 Snake River Id
    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 ArcGIS. Do not save your work.
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Resources


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