Food and Water Supplies Under Stress
Warm-up: Looking at Agriculture
The purpose of this activity is to emphasize the limited supply of freshwater worldwide. Freshwater, bodies of water containing low concentrations of salt, is being used at a higher rate than it is being renewed, and climate change threatens to further reduce its availability. Demonstrate the availability of freshwater by drawing one liter of water into a bottle (one liter being 34 fluid ounces). Pour 33 ounces of the water (roughly 97%) into a second container. The water in the second container represents the amount of water on Earth that is salt water, and the remaining water in the first bottle is the amount of freshwater on Earth. Next, pour 1 ounce of the remaining water from the first bottle into a third container. This amount (about 2% of the liter) represents the amount of freshwater that is locked in ice caps and glaciers. The remaining water in the original bottle, 0.3% of the liter, is the amount of freshwater available for everyday use. This represents all the potable water found in rivers, lakes, streams, and groundwater aquifers on Earth. This demonstration shows the relatively small amount of freshwater water available to support all the living beings on the planet.
Connect the idea of limited water supplies to the students’ activities by asking them to consider how much water they had in their last meal. Make sure they include the water that was included in the actual food to understand that consuming water means more than drinking from a glass. After this, have them consider the water involved in growing the food that they ate, or that supported the animal that produced their meal. A table of common livestock and the amount of water daily needed to support them is listed below.
Gallons of water/day (average)
Turkey(for every 100)
Once they have begun to understand the enormous amount of resources that goes into producing the food that they eat, provide the students with some numbers on water use in agriculture. These numbers reflect the amount of water it takes to produce the specified amount of each product:
Coffee, 2 lbs: 5,200 gallons
Quarter-pounder: 2,900 gallons
Milk, 1 gallon: 2,000 gallons
Cotton t-shirt: 1,800 gallons
Cheese, 2 lbs: 1,300 gallons
Rice, 2 lbs: 1,300 gallons
Sugar, 2 lbs: 750 gallons
Wheat, 2 lbs: 250 gallons
Now begin to discuss the impact of climate change on agriculture. Remember that climate change will have different impacts at different regions around the globe, so while some places will experience extreme weather events and flooding, other parts will likely experiences drought. Either way, these changes in climate will greatly affect the ability of people to produce food. Historically, humans have overcome agricultural obstacles through selective breeding and irrigation. Plants and animals are selectively bred to cultivate certain traits desirable for agriculture, such as producing more fruit or having a higher tolerance for heat. Irrigation redirects the flow of a naturally occurring body of water to assist in crop production. Often, water is removed at a rate faster than can be replenished, and in cases where climate change causes drought, irrigation may cause water supplies to dwindle or dry out. On the other hand, floods in other areas used to a lower flow may destroy crops and livestock.
On a broad scale, as world temperatures climb agricultural zones will shift away from the hot equator and toward the increasingly temperate poles. Areas such as Iceland and Russia have recently found themselves able to grow crops they could never grow before. However, the polar regions have weaker sunlight that shines for a shorter time than regions closer to the equator. This will lead to a shorter and less productive growing season. Water supplies will also become more limited as ice caps melt and sea levels rise, allowing salt to infiltrate fresh groundwater. The EPA lists some other possible impacts of climate change on agriculture:
- Lengthening the growing season in regions with a relatively cool spring and fall.
- Adversely affecting crops in regions where summer heat already limits production.
- Increasing soil evaporation rates.
- Increasing the chances of severe droughts.
- CO2 rise helping plant growth but offset by effects of temperature and precipitation changes.
It is also important to consider the impact of our current agricultural practices on the environment, and how we can be more sustainable in this field. The students will explore these areas further in the activities. The first activity will look at how climate change will affect agriculture, and the second will look at how the food we eat affects climate change.
Activity One: Adapting to Climate Change
Step 1: Break the class into small groups. Have each group select a place in the United States to establish a hypothetical farm. Ensure that there is considerable variation among the groups (for example, the Midwest, the Southeast, the Pacific Northwest, the Northeast, etc). Ask the students to do research on their area and determine what crops their climate canmaintain. Have them look at this Web site for help: http://www.agclassroom.org/teacher/ag_profiles.htm.
Next, students should research sustainable agriculture and describe what sustainable practices they could establish on their farms. Some examples include rotating crops to avoid leaching soil nutrients, minimizing green house gas emissions, sustainable irrigation and water use, avoidance of pesticides, and limiting use of fertilizers that pollute groundwater. To help them understand these terms, have the students fill out the worksheet at the end of the lesson plan.
Step 2: Have the students imagine that it is ten years later, and their farms are now being affected by climate change. Depending on the location of the farm, the effects will be different. To make things easier, you may use these simplified rules:
- Eastern and western coastal areas will experience flooding, especially Florida and other very low-lying areas.
- Southern coast will experience increased numbers of tropical storms.
- Temperature will rise several degrees in all locations.
- Southeast areas will experience a distinct dry season in the winter.
- Droughts and wildfires will be experienced throughout the Midwest and in California.
- The Northeast will experience changes in their ecosystem, such as the predominant trees switching from Maple to Oak.
- Alaska and Canada will experience a longer growing season.
Ask students to describe what new challenges are posed to their farm. Is their farm’s crop still able to grow under the new conditions? How is it affected by changing temperatures? Changing precipitation? Will climate change affect their income? Will other areas’ increased ability to produce crops (such as Canada) affect their farm’s profit?
Activity 2: Food and Climate Change
Step 1: Instruct each student to take an inventory of their food and water consumption for two days in their notebook. They should keep record of what foods they eat, how much water they drink, how many times they wash their hands, how long they stay in the shower, how many times they flush the toilet, and any other activity involving food or water consumption.
Step 2: In class or at home,have students examine the amount that they have consumed. To start, they can calculate their totally water usage using the US Geological Survey’s Water Usage Questionnaire at http://ga.water.usgs.gov/edu/sq3.html.
Step 3: After looking at water intake, it is time to turn to food. Provide the students with some information about the meat industry and its impact on the earth. Some issues to discuss are: deforestation to create pastures and for land to grow feed, water and energy needed to slaughter the animal and process the meat, carbon emissions from immense amounts of transportation to get food to the consumer, and soil erosion from overgrazing are all problems. According to a recent report by the United Nations Food and Agriculture Organization, livestock generate 18% of green house gas emissions. Much of this is from generating 65% of human-related nitrous oxide (mostly from manure) and 37% of human-induced methane. Both of these are much stronger greenhouse gases than CO2.
With this information in mind, have the students estimate the ecological footprint, the impact of their individual lifestyle on the environment, of their own food consumption for the two days they recorded using the table below. You can also assign your students to use the Earth Day Network ecological footprint quiz available at: http://www.earthday.net/footprint/.
CO2 equivalent emissions of various foods:
lbs CO2/100 Cal
beef (grain fed)
fish (average value)
vegetable (average value)