DAIRY FARMING AND HUMAN POPULATION:

A CHOROPLETH MAPPING ACTIVITY

Douglas Bradley

Preview of Main Ideas

Which states have the most dairy cows? Dairy farming has changed a great deal over the years yet tradition plays a large role in dictating where dairy farms and cows are located in the United States. In this lesson students apply problem-solving skills to try to answer the question above.

Connection with the Curriculum

This lesson can be used in geography, social studies, or agriculture class.

Teaching Level: Grades 5-8 (This lesson can be adapted to grades 9-12.)

Objectives Classification Outline (Also see objectives classification matrix below.)

Objective #1: The student will be able to hypothesize about the location of dairy cows n the united states and use data to construct a choropleth map showing numbers and distribution.

Essential Element: The World in Spatial Terms.

Standard #1: How to use maps and other geographic representations, tools, and technologies to acquire, process, and report information from a spatial perspective.

Knowledge Statement #2: How to make and use maps, globes, graphs, charts, models, and databases to analyze spatial distributions and patterns.

Skill Set #2: Acquiring geographic information.

Skill #2: Use maps to collect and/or compile geographic information.

Theme: Location.

Objective #2: The student will be able to compare their choropleth maps and identify patterns that exist between the location of dairy cows and the location of other elements, such as human population.

Essential Element: The World in Spatial Terms.

Standard #3: how to analyze the spatial organization of people, places, and environments on Earth's surface.

Knowledge Statement #1: How to use the elements of space to describe spatial patterns.

Skill Set #5: Answering Geographic Questions.

Skill #2: Make generalizations and assess their validity.

Theme: Location, Regions.

Materials

1.                  United States outline map for the mapping of data.

2.                  Data on dairy cow population (US Census of Agriculture).

3.                  Data on other aspects of agriculture (US Census of Agriculture).

4.                  Data on total human population of the United States (US Census, World Almanac).

5.                  Colored pencils or markers.

6.                  Overhead projector and overhead transparency of each map or PCUSA or MacUSA.

Suggestions for Teaching the Lesson

Opening the Lesson

Organize students into groups and have them answer the following question:  Which state has the most dairy cows?  Write the groups’ responses on the board.  Ask each group to select one state from the list that probably has the largest number of dairy cows.  Ask groups to provide reason(s) why the state chosen by their group probably has a high number of dairy cows.  Discuss generalizations (statements believed to be true based on data or prior knowledge) with the class.  Have each group write a generalization that explains why a high number of dairy cows live in the state they chose.  Explain to students that they have formed a hypothesis that attempts to determine which state as the most dairy cows while explaining the spatial distribution.

Developing the Lesson

1.                  To test their hypotheses students need data to prepare a type of quantitative analysis.  The procedure that they will use to test the data is basic chorpleth (quantity) mapping.  To begin with, students need to collect (from US Census of Agriculture) or be provided with the data that shows number of dairy cows per state (See Handout number 1).  From this compiled information help the students organize the data into four relatively equal groups called quartiles.  (Note:  See choropleth mapping instruction sheet included with this lesson.)  Choose a common color scheme (four colors needed) for the students to use.  For example the darkest color might show the states with the most dairy cows and the lightest color could show the state with the least dairy cows.  The next step is to have each student construct a choropleth map that shows the number of dairy cows per state.

2.                  Next assess the list of hypotheses and select only those which can be mapped by the students.  For example, one group may suggest that dairy cows live where alfalfa is produced, another group may suggest that dairy cows live where there are low temperatures.  A choropleth map can be made for the alfalfa (if the data are available to you), but a choropleth of temperatures is difficult to construct because of variations within the state, but not impossible.  A group that hypothesizes that alfalfa is an important factor would then have to use the same procedure used earlier to organize and color their choropleth map.  Typical hypotheses usually include human population, alfalfa (hay, grasses, etc.), corn, soybeans, location of beef cattle, etc.  Those groups that hypothesize that an unmappable factor influences location of dairy cows has to choose a topic from our mappable list.

Concluding the Lesson

When students are finished with their maps it is time for them to assess their hypotheses.  The students will observe the maps, analyze them, and speculate as to whether or not their hypotheses tend to be valid.  Ask the students to look for patterns (make correlations) that exist between the maps.  They will recognize that a direct visual correlation appears to exist between states with high human populations and high number of dairy cows.  Ask students why this correlation seems to exist.  Direct the discussion towards the fact that, before refrigerated transportation vehicles, milk had to be kept close to the consumers so it would not spoil (a perishable item).  Other factors might include tradition, origin of settlers who raised dairy cows, age of farmers, and value of farmland.

Extending the Lesson

1.                  Take students on a trip to a nearby dairy farm.  Ask them to evaluate the setting and resources of the farm to determine if it possesses all the qualities that they would like to have at the farm.  What changes would they make?  Why?

2.                  Another opportunity for students would be to look at dairy farming in their state by county to see if the relationship between human population and dairy cow population seems to exist within the state.  Again, a hypothesis could be formed and visually tested using choropleth mapping.

Assessing Student Learning

Ask students if they were determining where to locate a major dairy farming facility what factors should be considered.  Ask them to use the list that they generate to look at the United States and select a state that seems to meet those criteria.  Next, have them investigate that particular state to narrow their location to a particular part of the state.

GEOGRAPHY STANDARDS CLASSIFICATION MATRIX – GRADES           5-8   

Title: Dairy Farming and Human Population: A Choropleth Mapping Activity          Author:          Douglas Bradley

Note:  See also Objectives Classification Outline in the lesson.

Handouts

Handout A

CHOROPLETH MAPPING

The following procedure is recommended for constructing a choropleth map.  It can be used with any data that ranges in value and can be associated with geographic regions, e.g. counties, states, countries.

1. Determine class intervals by first finding the range of the data.  Select the number of classes to be used for your map and calculate the interval of each class.  Here is one method for determining class intervals.
   a.    Inspect your data sheet to identify extreme values, such as the number of tornadoes in Texas.
   b.    Eliminate extreme values for purposes of calculating range in the data.
   c.    To calculate range, determine the highest and lowest values in the data.
   d.    Subtract these two numbers in order to calculate the range for the data.  Be sure to exclude data for Texas
          before calculating ranges, but include it in the highest group for mapping.
   e.    Divide the range by the number of classes planned for your map.  Three to seven mapping classes will be
          adequate for most data sets.  Experiment with three and four intervals for the tornado data to determine which
          one provides the most useful mapped patterns.  The number produced by the division will be the range for each
          class.  (Note:  The best number of classes to use is the one that gives you the most useful information.  Generally,
          between three and seven works best.  If too few classes are used, important details may be lost.  Too many
          classes mean that the map gets cluttered with too much detail.)
          Example of class intervals:

                  The map maker may choose to adjust the classes if there are outliers or clusters of information that become
                   hidden in the process outlined above.
            f.    Often the highest and lowest classes will contain a larger interval because the range does not divide evenly.
                  Construct classes so that the numbers in one class do not overlap those in adjacent classes.

2. Arrange a color code or shading pattern for each class.  Colors or patterns should increase from light to dark, from lowest to highest class.

3. Identify the proper class interval for each country or region and color or shade the state on an outline map.  Title the map, place a legend on the page, and include the source for the data displayed.

4. If other data sets (e.g., precipitation amounts) are mapped to find relationships, students should consider the following as they complete their analysis.
   a.    Describe the patterns observed on the maps.
   b.    What accounts for the variation?
   c.    Discuss the factors that could lead to the range of outcomes within the distribution.
   d.    Discuss the relationships between the regional patterns.  Is the relationship positive or negative?  (Are the states
          with the highest rate of one variable the same states with the highest rate of the other variable?  If so, there is a
          positive correlation.  if the states that are highest in one variable are lowest in another, the correlation is
          negative.)
   e.    Discuss whether or not the factors that contribute to the patterns in one variable affect the patterns of another.

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Handout B

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Handout C

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