Do You Have Change?

Coastal Change Analysis / Grades 9-12 / Earth Science, Life Science




Focus Question

How can scientists monitor changes in the ways land is used in coastal areas?

Learning Objectives

Links to Overview Essays and Resources Needed for Student Research

http://oceanservice.noaa.gov/topics/coasts/monitoring/
http://www.csc.noaa.gov/digitalcoast/data/ccapregional/
csc.noaa.gov/crs/lca/ccap.html

Materials

Click here for a printable copy of this worksheet 204Kb

Audio/Visual Materials

None

Teaching Time

One or two 45-minute class periods

Seating Arrangement

Classroom style, or in groups of 3-4 students

Maximum Number of Students

30

Key Words

Change table
Landsat Thematic Mapper
Georeferencing
Pixel
Land use
Coastal change
Monitoring

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Background Information

Coastal monitoring refers to periodic measurements of physical, chemical, biological, and meteorological factors that may affect the use and quality of coastal resources. For example, such factors may include temperature, salinity, the presence of chemical contaminants, biological species and their life stages (eggs, juveniles, adults, etc.), rainfall, and storm events. NOAA’s National Ocean Service (NOS) supports 28 different monitoring systems to provide key pieces of information needed to protect marine resources and control the ways in which they are used.

NOAA’s Coastal Change Analysis Program (C-CAP) uses data from Landsat satellites to detect changes in coastal land cover. Often, these changes are the result of human activities such as urban development, forestry, and use conversion (such as converting agricultural land to residential housing). Some changes, though, are the result of natural processes such as erosion or succession (for example, the succession from grassland to shrub vegetation to forest). One of the immediate objectives of C-CAP is to develop a baseline data set that describes land cover throughout the entire coastal zone of the United States. By comparing these data with satellite imagery obtained at a later date, changes in land cover can be detected, and trends can be monitored over time.

It is important to understand the distinction between “land cover” and “land use.” Land cover is the visible physical landscape, which includes natural features (forests, water, rocks, etc.) as well as features constructed by humans (buildings, parking lots, etc.). Land use is the economic and cultural activities that take place in a given location (residential, commercial, agricultural, industrial, etc.). Some land uses produce visible land cover features (highways, agricultural fields, etc.), but land cover does not always coincide with a specific land use. A building, for example, might be a school, hotel, retail store, or prison; very different land uses may appear as the same type of land cover. Satellite imagery are most useful for determining land cover. Land use can sometimes be inferred from land cover, but usually requires other survey methods.

The Landsat images used by C-CAP consist of many individual blocks known as “pixels” (a term derived from the phrase “picture element”). Each pixel represents an area of ground, and the size of this area depends upon the characteristics of the sensor used to capture the image. C-CAP uses imagery from the Landsat Thematic Mapper (TM), which collects pixels that each represent a 30 meter x 30 meter area of land. Anything on the landscape that is smaller than 30 meters in diameter will not be distinguishable from other small features in the same area. To detect changes in land use over a specific time period an image obtained at the beginning of the time period is compared with an image obtained at the end of the time period. Different land uses have different spectral characteristics (for example, forested lands reflect more green light than beaches) when viewed by the TM. By knowing the spectral characteristics of different land uses, each pixel in a TM image can be classified as a specific land use. Computer analysis is used to compare the classification of each pixel in the first image with the classification of the corresponding pixel in the later image. The results of this comparison are usually summarized as a “change table.” A change table is a matrix of columns and rows similar to a spreadsheet. The first vertical column and first horizontal row list all of the land use categories used in the analysis. The first column represents categories in the first (earlier) image, while the first row represents categories in the later image. Reading the chart from left to right, each cell in the matrix shows the amount of land (typically “acres”) that changed from one category in the first image to another category in the second image. The central diagonal cells in the chart represent areas of land whose category is the same in both images (that is, areas of land whose category did not change during the period of time represented by the two images).Visit http://www.csc.noaa.gov/products/sccoasts/html/scmatrix.htm for an explanation and example of a change table.

In this lesson, students will construct a simple change table to become familiar with this concept, and then use an actual change table to make inferences about land use changes in a coastal area.

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Learning Procedure

  1. In preparation for this lesson, review the introductory pages on the Coastal Change Analysis Program Web site (http://www.csc.noaa.gov/crs/lca/ccap.html) and the explanatory materials on change tables cited above, and the “Land Use Change Worksheet.”
  2. Lead a brief discussion in which students “brainstorm” events that cause land use changes in coastal areas. This list should include “natural” events as well as human activities. Introduce the concepts of change tables and pixels. Tell students that their first assignment is to construct a change table that summarizes data on land use changes on an imaginary island over a five-year period. Give each student or student group a copy of “Land Use Change Worksheet,” and have them complete Part A.
  3. Review students’ results for Part A. Tables 1 and 2 should resemble those below:
  4. Table 1

    Pixel 1990 Land Cover 1995 Land Cover
    A5 GA GA
    A6 BA BA
    B4 GS GS
    B5 GS BA
    B6 GS BA
    C2 DL DL
    C3 DL DL
    C4 DH DH
    C5 DH DH
    C6 WL BA
    C7 WL GS
    D1 AG AG
    D2 DL DL
    D3 DL DH
    D4 DH DH
    D5 DH DH
    D6 GA BA
    D7 AG AG
    E1 AG AG
    E2 AG DL
    E3 DH DH
    E4 DH DH
    E5 DH DH
    E6 BA BA
    E7 BA BA
    F2 AG DL
    F3 BA BA
    F4 WL DH
    F5 GS DH
    F6 GS GS
    G3 MF MF
    G4 MF DH
    G5 MF DH
    G6 GS GS
    H4 MF MF
    H5 MF MF

    Table 2

    To 1995
    DH MF WL GS AG DL BA Total
    Acres
    From 1990

    DH
    7 0 0 0 0 0 0 7
    MF 2 3 0 0 0 0 0 5
    WL 1 0 0 1 0 0 1 3
    GS 1 0 0 4 0 0 2 7
    AG 0 0 0 0 2 2 1 6
    DL 1 0 0 0 3 3 0 4
    BA 1 0 0 0 0 0 4 4
    Total Acres 12 3 0 5 5 5 8  

    Click here for a printable copy of Table 1 and 2 72Kb

    Be sure students understand what is represented by the individual cells in the matrix, and that the central diagonal cells represent areas of land whose category did not change during the five-year period. Students’ observations about the change table should include:

    • All wetlands present in 1990 were converted to other land uses by 1995.
    • Pixels with high density development in 1990 did not change.
    • Half of the area classified as agricultural in 1990 was converted to other uses by 1995.
    • More area was converted to high density development than to any other land use category.

    Point out that actual images provided by the Landsat Thematic Mapper include many more pixels than the two images for “Hokey Island,” and that computers are used to compare pixels between the images acquired at different times. Be sure students understand the concept of using a coordinate system to identify the location of specific points on Earth (georeferencing).You may also want to discuss some of the coordinate systems used for georeferencing (see page 9 of the Global Positioning Tutorial at http://www.oceanservice.noaa.gov/education/tutorial_geodesy/geo09_gps.html.

  5. Have students complete Part B of the worksheet, then lead a discussion of their results. The following points should emerge during this discussion:
    • Cultivated land, wetlands, and forested land are the top three land cover types in the Mermentau River Basin. Be sure students understand that the “Total Acres”column represents the total acres for each class in the 1990 (“from”) data. Total acres for the 1995 (“to”) data are given in the “Total Acres”row.
    • Students should infer that agriculture, forestry, fisheries and recreational uses might be associated with these types of land cover.
    • Grasslands, forested, and scrub/shrub categories had the highest number of acres changed between October 1992 and February 1996.
    • These land cover categories are part of the succession from bare earth to mature forest. The sequence is actually a cycle: bare earth, to grasslands, to scrub/shrub, to mature forest, and eventually back to bare earth. There is no specific “starting point”; a snapshot of a single area at one point in time may observe any of these steps, as well as transitions between steps.
    • Other evidence of this succession in the change table includes the following: 50,942 acres of scrub/shrub converted to forested land; 81,662 acres of grassland converted to scrub/shrub; 67,769 acres of forested land converted to grassland (presumably the bare earth step took place between October 1992 and February 1996); in fact, all of the largest conversions involved this succession cycle.
    • 3.3% of wetlands were converted to other land cover categories (41,033 – 1,213,802).
    • The majority (97%) of wetland conversions were to the “Water” category, so students may infer that the wetlands were not really “lost.”

Tell students that most of the conversion from “Wetlands” to “Water” was the result of changes in the amount of floating aquatic vegetation, which varies seasonally and from year to year. For this reason, wetland loss is not considered to be a serious problem in the Mermentau River Basin. Be sure students understand that this is only because most of the wetlands were not really lost, and that the loss of 41,000 acres of wetland would be considered very significant and serious in most areas.

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The Bridge Connection

The Bridge is a collection online marine education resources. It is a convenient source of useful information on global, national, and regional marine science topics. Educators and scientists review sites selected for the Bridge to insure that they are accurate and current.

www.vims.edu/bridge – In the navigation menu on the left, click on “Research and Data Connections,” then “On-Line Data” for links to real-time data sets that can be incorporated into your lesson plans, as well as pointers on how to use real-time data.

The “Me” Connection

Have students write a brief essay describing why the ability to detect changes and trends in land cover could be of personal importance, and how they might use this information. For example, how could a downward trend in wetland acreage be personally significant; and if such a trend were detected, what could anyone do about it? If students have difficulty with this, you may want to brainstorm some of the functions or benefits of the resources that are changing. Wetlands, for example provide buffers against erosion and storms, wildlife habitat, etc.

Extensions

Visit http://www.csc.noaa.gov/products/datasites/ for links to examples of Internet resources for coastal geospatial information.

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Resources

http://www.csc.noaa.gov/crs/lca/ccap.html – NOAA Coastal Services Center Web page for the Coastal Change Analysis Program

http://www.csc.noaa.gov/crs/ – NOAA Coastal Services Center Web page for the Coastal Remote Sensing Program

www.geographynetwork.com – Web site for the Geography Network, which is a global network of geographic information users and providers that supports sharing of geographic information and provides access to many types of geographic content including dynamic maps, downloadable data, and more advanced Web services.

http://ltp-education.gsfc.nasa.gov/ – Education and Outreach website for NASA’s Laboratory for Terrestrial Physics

http://landsat.usgs.gov/ – USGS’s Landsat Web site

National Science Education Standards

Content Standard A: Science as Inquiry

Content Standard D: Earth and Space Science

Content Standard E: Science and Technology

Content Standard F: Science in Personal and Social Perspectives

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Ocean Literacy Essential Principles and Fundamental Concepts

Essential Principle 2. The ocean and life in the ocean shape the features of the Earth.

Essential Principle 6. The ocean and humans are inextricably interconnected.

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Do You Have Change?

Student Worksheet - Land Use Change, etc.

Click here for a printable copy of the student worksheet 204Kb

Part A

A major responsibility of NOAA’s Coastal Change Analysis Program (C-CAP) is to document how land cover in coastal areas changes from one time period to the next. To do this, C-CAP uses satellite images (primarily the Landsat Thematic Mapper) to categorize land cover in coastal wetland habitats and adjacent upland areas. Extensive ground checks are used to verify that interpretations of satellite images are accurate with respect to land cover. By comparing images of the same area acquired at different times, it is possible to detect changes in land cover and make inferences about land uses that account for observed changes.

Data on changes in land use are often summarized in change tables. To get an idea of what a change table means, let’s analyze two images of land use on a fictitious island in 1990 (Figure 1) and 1995 (Figure 2). Land use images consist of many individual blocks known as “pixels.” Each pixel represents an area of ground, and the size of the pixel depends upon the characteristics of the sensor used to capture the image. To keep things simple, the data for Hokey Island consist of very large pixels, so there aren’t very many of them. In reality, images obtained by the Landsat Thematic Mapper consist of pixels that are 30 meters x 30 meters, so there are many more pixels in these images (and a lot more data to analyze!).

The first step in this analysis is to identify the exact location of each pixel so that pixels representing the same location in the two images can be compared. One way to do this is to identify each pixel with the the latitude and longitude of the area it covers. Other systems commonly used include the Universal Transverse Mercator system and State Plane Coordinate System. Again, to keep things simple, we’ll just use letters and numbers to identify the row and column corresponding to each pixel.

Next, fill in Table 1 to summarize land cover for each pixel in 1990 and 1995. Notice that the images exclude pixels that cover less than half of Hokey Island, and that some pixels (on the edges) also include areas that are not part of Hokey Island. This is why smaller (and therefore more numerous) pixels give a more accurate estimate of land cover.

Figure 1
Hokey Island Land Use, 1990



Hokey Island Land Use, 1990

Figure 2
Hokey Island Land Use, 1995



Hokey Island Land Use, 1995
 

Table 1

Pixel 1990 Land Cover 1995 Land Cover
A5    
A6    
B4    
B5    
B6    
C2    
C3    
C4    
C5    
C6    
C7    
D1    
D2    
D3    
D4    
D5    
D6    
D7    
E1    
E2    
E3    
E4    
E5    
E6    
E7    
F2    
F3    
F4    
F5    
F6    
G3    
G4    
G5    
G6    
H4    
H5    

Now it’s time to construct a change table. Table 2 is a matrix with land use categories for 1990 in the first column, and land use categories for 1995 in the first row. Reading the chart from left to right should show how many pixels for each land use category in 1990 changed to another category in 1995. Use Table 1 to fill in Table 2. The central diagonal cells with bold outlines show how many pixels for each category did not change between 1990 and 1995. What trends does the change table reveal?

Table 2


To 1995
DH MF WL GS AG DL BA Total
Acres
From 1990

DH
               
MF                
WL                
GS                
AG                
DL                
BA                
Total Acres                


Part B

Table 3 is a change table documenting changes in the Mermentau River Basin, Louisiana, between October 1992 and February 1996. Use this table to answer the following questions:

  1. What are the top three land cover types in the Mermentau River Basin?
  2. ______________________________________________________________________________

    ______________________________________________________________________________

    ______________________________________________________________________________

  3. What uses might be associated with the dominant land cover types?
  4. ______________________________________________________________________________

    ______________________________________________________________________________

    ______________________________________________________________________________

  5. Which three land cover categories had the highest number of acres changed between October 1992 and February 1996?
  6. ______________________________________________________________________________

    ______________________________________________________________________________

    ______________________________________________________________________________

  7. Describe the steps in an ecological succession that includes these land cover categories.
  8. ______________________________________________________________________________

    ______________________________________________________________________________

    ______________________________________________________________________________

  9. Is there other evidence of this succession in the change table?
  10. ______________________________________________________________________________

    ______________________________________________________________________________

    ______________________________________________________________________________

  11. What percentage of wetlands were converted to other land cover categories?
  12. ______________________________________________________________________________

    ______________________________________________________________________________

    ______________________________________________________________________________

  13. Which land cover category accounts for the majority of wetland conversions in this change table? How serious is the loss of wetlands in the Mermentau River Basin?
  14. ______________________________________________________________________________

    ______________________________________________________________________________

    ______________________________________________________________________________




Table 3

Click here for a printable copy of the student worksheet 204Kb


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