Geog. 143 -- Global Environmental Change

Exercise 7:  Population and the Global Environment

By now it should be apparent that population--its patterns and variations through time--is a major element in understanding global environmental change.  This situation arises because

• population growth has been a important driver of both land-cover change and climate change

• future population trends are a key component of GHG emissions scenarios

• disparities between population levels and agricultural productivity underlie the idea of "food security" and contribute to political unrest.

The first couple of questions will again use some of the maps in  the Atlas of the Biosphere provided by the Center for Sustainability and the Global Environment at the University of Wisconsin -- Madison (http://www.sage.wisc.edu/atlas/).

Here are the links to the maps and to the copies.  See Exercise 5 for details on how to use the maps.

http://geography.uoregon.edu/bartlein/courses/geog143/labs/UW-SAGE-atlas.pdf
http://geography.uoregon.edu/bartlein/courses/geog143/labs/UW-SAGE-atlas-copy.pdf

The particular maps used here include net primary productivity (NPP), cropland intensity, agricultural suitability, and population.

1.  Biological productivity and population

Compare the spatial pattern of productivity (as indexed by NPP), cropland intensity, and agricultural suitability.  (It's a little tricky to compare three things at one, but not impossible.)

Q1:  Describe the general relationship among NPP, cropland intensity, and agricultural suitability.  (Do regions with high NPP always always have high cropland intensity and agricultural suitability?)  Identify some regions with high cropland intensity and low NPP.  Where are these located?  Is there something else involved in determining agricultural suitability than simply productivity?

2.  Population vs. agricultural suitability

Compare the map patterns of population and agricultural suitability.

Q2:  Where are the regions with high suitability but low population, and where are the regions with low suitability and high population.  Using what you may know about contemporary geopolitical issues, what do these patterns suggest about the role of food security in conflicts around the globe?  In other words, what are the productivity/suitability characteristics of current geopolitical hotspots?

3.  Population change

The next couple of questions make use of "population pyramids" that display the numbers of males and females as a function of age "cohorts" using a particular style of bar chart.  Population pyramids are briefly explained in a summary publication produced by the U.S. Census Bureau:

 http://www.census.gov/ipc/prod/wp02/wp02-1.pdf

Here is a local link to the .pdf

Although the summary was dated 2002, it was released in 2004, and is probably still an adequate overview, despite the ever increasing incidence of HIV/AIDS, and the continuation of drought-related famine in many regions.

Population pyramids are available online at:  http://www.census.gov/ipc/www/idb/ and a direct link to the population pyramid page is:  http://www.census.gov/ipc/www/idb/pyramids.html (Enjoy the nice colors!)

Here are local links to some image files:

• United States

• Afganistan

• Japan

• Russia

• South Africa

To see how population pyramids work, take a look at the ones for the U.S.:

1. Use the scrolling list box to select "United States"

2. Set type of output to "Summary (2000, 2025, 2050)"

3. Select graph size to small, and

4. Click on the "submit query" button

The way to interpret population pyramids is to note for the pyramid for a specific time

• when each particular age cohort was born, and

• what might have transpired then and since that time. 

For example, on the population pyramid for the United States for 2000, note the bulge in the pyramid created by the 35-39 and 40-44 year old cohorts.  Those cohorts contain people born between 1956 (44 years before the pyramid date) and 1965 (35 years before the pyramid date)--the "baby boomer" generation.  Note also the "baby boom echo" bulge created by people the 5 to 19 age cohort in 2000.  Also note how these bulges move up the pyramids over time (e.g. in 2025 and 2050).

It is also possible to click on the "dynamic" output type, which provides an animation of individual population pyramids.  This is handy for exploring trends, but because it's not controllable, this display can be difficult to use for examining particular years.

The way to understand how population pyramids "work" is to examine one (i.e. the United States) where you have some idea of what is going on, and then look at others.

Examine the population pyramids for Afganistan, Japan, Russia and South Africa.

Q3:  For each country describe the basic shapes of the pyramids and their trends, and note what those shapes suggest about potential future population growth trends in each country.

Q4:  Next, see if you can figure out what contributes to some of the specific features in the pyramids.  For example, note the relatively low numbers in the 55-59 age cohort on the 2000 pyramid for Russia.  Why might relatively few children have been born in Russia between 1941 and 1945?

It's easy enough to look at the population pyramids for neighboring countries for the ones listed above, which may help you figure out what's going on.