How Much Land Does It Take To Produce Your Food?
Janis Lariviere, Barbara Mannion, O. Truman Holtzclaw, Randyl Warehime, and Arthur Broga
1991 Woodrow Wilson Biology Institute
Overview
In this investigation, you calculate the amount of land required to produce the food eaten by an
individual for one year and compare the amount of land required to produce animal versus plant
products.
Background:
Humans require energy and their energy is obtained from food. Energy moves from its source in
the sun through the photosynthetic organisms that make that energy available to living things
(producers) and then through organisms that eat other organisms (consumers). Land therefore
yields fewer kilocalories per square meter per year in animal products than in plant products.
Energy is lost in the transition from producers to consumers. (respiration, heat loss, animal waste)
Plants can be divided into two groups, C-3 and C-4, based on the photosynthetic and respiratory
pathways they utilize. Under the right conditions C-4 plants such as sugarcane and corn
photosynthesize two to three times as fast as C-3 plants. C-4 plants are also more efficient because
they don't lose energy due to photorespiration which frequently occurs in C-3 plants. C-3 and C-4
plants are separated on the Analysis Sheet because the C-3 plants are less energy efficient. A final
point to remember in dealing with food energy, a food Calorie used by nutritionists is equivalent to
a kilocalorie (kcal) used by chemists and physicists.
Procedure:
1) Record the types and amounts of food eaten during a 24-hour period. Be sure to count
everything, not just what is eaten at meals - snacks, candy, etc. too. If you record your food
intake for more than one day, just average your results in step 2 to get the amount consumed
in a single day.
2) Using calorie counter references, determine the total number of calories taken in during those
24 hours. Multiply this amount by 365 to determine the total number of calories taken in during
a year.
3) Use the attached Analysis Sheet for Trophic Ecology of Humans and the students' calorie data
to determine the square meters of land required to support the individual. Do this by
determining the number of calories that fall into each food category and divide each of these
values by the "yield".
a) Add all the values in the "square meters of land" column to arrive at the total land required
to support the individual.
b) Add the values in each subgroup, C-3 plants, C-4 plants, and animal products, to compare
plant and animal land requirements.
4) Calculate a class average for the square meters of land required to support an individual.
5) Assuming a football field/soccer field is 5,000 square meters, how many fields do you need to
support an average member of your class for one year?
6) Calculate the amount of land (in m2) required to support the world’s population for one year.
7) Examine a world atlas to determine the total surface of arable land on earth (the land that can
be farmed). Convert this number into square meters, if it is not already in those units.
8) If everyone on earth ate as the average member of your class did, what percent of the earth
would be needed to produce that amount of food? To calculate this, divide the amount of land
needed to support the world’s population for one year by the total surface area of the land on
earth, and multiply by 100.
9) Is there sufficient land to meet the needs of today’s people? EXPLAIN.
10) Comparing land required to produce an equal amount of plant versus animal calories:
a) Choose one plant product (e.g. rice) and one animal product (e.g. beef) from the Analysis
Sheet for Trophic Ecology of Humans. Any foods from the Analysis Sheet could be used.
b) Assume that an individual takes in 200 calories of each product in one meal.
c) Divide the 200 calories by the yield from the Analysis Sheet.
d) Discuss the implications of vegetarian versus non-vegetarian diets. How would this affect
the results in the table of “Land Needed for Food”?
OPTIONAL:
11) Calculate the amount of land required to support the following groups for one year: your class,
your school, your community, your state, the USA.
12) Assuming a football field/soccer field is 5000 square meters, how many fields does a student
need to support him/herself for one year?
13) On maps of your community and/or state, shade in the land area needed to support your
school, community, and state. [To make this easier mark grids on the maps showing square
kilometers. Students need to convert the square METERS of land needed to square
KILOMETERS of land by dividing the value by 1 million. 1 mile = 1.6 kilometers.]
Resources:
Brewer, Richard and M.T. McCann, Laboratory and Field Manual of Ecology, Saunders College
Publishing, Philadelphia, 1982.
CALORIE COUNTERS:
1. Count Calories - Calories Count! David McKay Company, Inc., New York, 1980.
2. Editors of Consumer Guide, Calorie, Carbohydrate and Fat Counter, Publications
International, Skokie, Illinois, 1982.
3. Fat and Cholesterol Counter, American Heart Association, Random House, 1991.
4. Food Values: Calories, Harper and Row, New York,1990.
5. Netzer, Corinne, The Complete Book of Food Counts, Dell Publishing, New York, 1988.
6. Williams, Walden, Vest Pocket Calorie Counter, Doubleday, New York, 1990.
Analysis Sheet for Trophic Ecology of Humans
Food Category
Your Daily
Consumption
(kcal/day)
Your Annual
Consumption
(kcal/year)
Yield
(kcal/sq
m/year)
C – 3 PLANTS
Bread
Wheat, cereal
Oranges,
grapefruit
Frozen orange
juice
Peanut butter
Rice, rice
cereal
Potatoes
Carrots
Other
vegetables
Apples
Pears, peaches
Vegetable oil
Margarine
Beet sugar
650
810
1000
410
920
1250
1600
810
200
1500
900
300
300
1990
SUBTOTAL
C – 4 PLANTS
Cane sugar
Soft drinks
Corn cereal
Corn
3500
3500
1600
250
SUBTOTAL
Square Meters of
Land
Required to Support
You
(Yearly Consumption
÷ Yield)
ANIMAL PRODUCTS
Milk
Cheeses
Eggs
Chicken
Pork
Beef
Fish (frozen)
420
40
200
190
190
130
2
SUBTOTAL
TOTAL
Source: Brewer, Richard and M. T. McCann, Laboratory and Field Manual of Ecology, Saunders
College Publishing, Philadelphia, 1982.