Week 5: Monitoring Invasive Species

Using AEJEE to Analyze and Predict Invasions

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

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.

Launch AEJEE and Orient the Map for the Investigation

• Launch AEJEE 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 ESRI/AEJEE/Data/Invasive_SpeciesAE and select the file inv_spc.axl. Then click Open.
  
• Once the map opens, turn on the US Rivers and Tamarix layers. Use the Zoom In tool to click and drag a box, around the contiguous United States.
  
  Show me how
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  1. Turn on the US Rivers and Tamarix layers by clicking in the checkbox next to their names.
     
  2. Use the Zoom In tool to click and drag a box, around the contiguous United States.
     
• 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.
Show me how
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Make Tamarix the active layer by clicking its name. Click the Zoom to Active Layer tool 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.



• Turn on the US States layer.

Investigate the Tamarix Invasion in the United States

• Make Tamarix the active layer by clicking its name.

• Click once on the Select Feature tool in the toolbar.
1. In the drop down menu, choose the Rectangle selection tool.
2. On the map, click and drag to draw a rectangle around a group of Southwestern states.
3. When the tool is released the selected Tamarix points are highlighted yellow. These points are selected because Tamarix is the active layer.
Show me how
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1. Click once on the Select Feature tool in the toolbar.
2. In the drop down menu, choose the Rectangle selection tool.



3. On the map, click and drag to draw a rectangle around a group of Southwestern states.



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



• Clear the selections by clicking on the Clear All Selection button.
• Change the active layer to US Rivers and repeat the selection process.
• How do the results differ?
  
  Show me the difference
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  US Rivers are selected on this map.
  
  Tamarix points are selected on this map.
  
• Clear the selections by clicking on the Clear All Selection button.

Where is the Tamarix invasion the most severe?

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?
   Show me the answer
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   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?
   Show me the answer
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   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.

Create a Spatial Query to Investigate the Extent of the Invasion

Buffer Southwest states to investigate the extent of the invasion

Make US States the Active layer and select Arizona with the Select Feature > Polygon selection tool.

1. Make US States the Active layer.
2. Click and hold on the Select Feature tool. Choose the Polygon selection tool. (Pictured to the right.)
3. Click just inside the state boundary of Arizona.
4. Release the selection tool, 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.
   Show me how
   Hide
   1. Make US States the Active layer by clicking its name.
   2. Click and hold on the Select Feature tool. Choose the Polygon selection tool.
      
   3. Click just inside the state boundary of Arizona.
      
   4. Release the selection tool, 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.
      

Use the Buffer tool 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 that is called "containment".

Buffer dialog box.

1. Click on the Buffer tool in the toolbar. The buffer dialogue box will open. (Pictured right)
2. Set the Buffer Distance to 1.
3. Set the Buffer Units to Meters.
4. Check the box "Use the buffer to select features from this layer".
5. In the pull down menu of layers, choose Tamarix.
6. Click OK. The buffer dialog window will automatically close and the selected points will be displayed on the map.
   Show me the details
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   1. Click on the Buffer tool in the toolbar. The buffer dialogue box will open.
   2. Set the Buffer Distance to 1.
   3. Set the Buffer Units to Meters.
   
   
   
   4. Check the box "Use the buffer to select features from this layer".
   5. In the pull down menu of layers, choose Tamarix.
   
   
   
   6. Click OK. The buffer dialog window will automatically close and the selected points will be displayed on the map.
      
      

Discover the results of the selection

1. Return to the map and make Tamarix the active layer.
2. Open the Attribute Table of Tamarix.
3. How many results are have been selected?
   Show me
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   Right click to open the attribute table of Tamarix.
   
   3333 Tamarix are recorded within the state of Arizona.
   
   

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

Show me the results

Hide

Clear the selections by clicking on the Clear All Selection button.

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 layer.
• Use the Zoom to extent of the active layer tool to zoom into the state of Arizona.
• Click on the AZ Rivers layer with the Identify tool to learn the names of the rivers in Arizona which are invaded by Tamarix.
• In the identify results box, scroll down to find the field "Name".
  
  Show me how to find this information
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  1. With the AZ Rivers layer active, click on a AZ River with the identify tool .
  2. In the identify results box, scroll down to find the field "Name".
     
     The map and results window.
     
     
• List several rivers that have been invaded by Tamarix.
  Show me the answer
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  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?
  Show me the answer
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  Answer: Wet areas such as wetlands or marshes are also suitable habitat.

Add Satellite Data to Connect Tamarix Spread with Vegetation Index

Adjust the layers on the map for the investigation.

• Turn off the US 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 AEJEE, choose Zoom to the extent of the 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.
Show me the map
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Show me more about the data in this image
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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.

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 > 2km 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?
Show me
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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 US Rivers layer on and off as needed and /or move the US Rivers layer above the Elevation layer.
Show me the map with elevation added
Hide
Map with Elevation > 2 km layer added.

• Based on the data in the Satellite NDVI image, Elevation > 2km, and the US Rivers layers, predict the direction that you think will Tamarix move in the next few years in the United States.


• Use the 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?
  Show me how to use the identify tool
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  With the US 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.
  
  
  2. Where would you send your land management team next?
  Show me the answer
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  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.
  3. What factors could be limiting the spread of Tamarix?
  Show me the answer
  Hide
  The invasion is limited by moist soils, temperature and water availability. There are no natural predators to Tamarix.
  
  
• Quit AEJEE. Do not save your work.

Resources

• Tamarix Information from the Desert Museum of Arizona
• [link http://www.desertmuseum.org/invaders/ invaders_tamarisk.php 'Salt Cedar' new]
• Tamarix Invasion White Sands National Monument
• The Worst Weeds - database from Nature Conservancy
• More information about Invasives
• Plant conservation alliance alien plant working group
• Illustrated Guide to Arizona Weeds
• How to Prevent the Spread of Noxious Weeds
• GIS aids in response to CA lake threatened by Pike
• iMap Invasives - online mapping of invasives