Activity 1: Slicing Up Earth’s Land Resources

Teacher Note: The following activity uses an apple to demonstrate the distribution of Earth's soil resources. Alternatively, you can provide the same demonstration using the Apple Land Use Model.

1. Project the Slicing Up Earth's Land Resources Slide Deck. This slide deck provides step-by-step instructions in the notes section. It also provides images to illustrate the type(s) of land discussed in each step.
2. Provide each student with a copy of the Slicing Up Earth's Land Resources activity sheet. Instruct them to fill in the chart while you perform the following demonstration:
   • Step 1: Hold up the apple. Explain to the students that this apple represents planet Earth.
   • Step 2: Cut the apple into four equal wedges. Three of these quarters represent the oceans, which occupy 75% of Earth’s surface. Set these aside.
   • Step 3: The remaining quarter represents land area, which occupies 25% of Earth’s surface. Take this quarter, and cut it into three equal wedges, so you have three 1/12 sections.
   • Step 4: Hold up one of these sections. This piece represents inhospitable land including deserts, mountains, and polar regions. This land is not suitable for people to live or grow crops. Set this section aside.
   • Step 5: Hold up the other two sections. These sections represent habitable land. This is land where people can live. Set one section down (it will be used in Step 7).
   • Step 6: Show one of the sections. This section represents habitable land where people live but crops are not grown. This includes nature preserves, public lands, and developed areas like roads, schools, houses, etc.
   • Step 7: Hold up the last section. This section represents the Earth's agricultural land, all the land on Earth that is used to grow food. Cut this section crosswise into four equal pieces, so you have four 1/48 sections.
   • Step 8: Hold three sections up. This land is used to graze livestock like dairy cows, beef cattle, pigs, and sheep and to grow crops to feed the livestock.

     Teach with Clarity Cattle, sheep, and goats spend the majority of their lives grazing grasses and other forages for feed. Their unique ruminant digestive system allows them to obtain nutrition from plants that other animals (or humans) cannot. Livestock animals also consume grain-based feeds consisting of field corn, soybeans, barley, oats, sorghum, etc. Step 8 of this activity illustrates the land used to feed the livestock that produce our meat, milk, eggs, and other animal-source products. More details can be found in the Background Agricultural Connections section of the lesson.

   • Step 9: Hold up the last section. This 1/48 section represents the amount of agricultural land on our Earth used to grow food crops for humans to eat. Examples of these crops include beans, fruits, vegetables, and grains.
3. Lead a discussion about land use and food production. Use the following questions to guide the discussion:
   • Why can't we grow food on all of the land on Earth? (Most crops cannot grow in soil that is too rocky, wet, or dry or in places that are too hot or cold.)
   • Does our food only come from agricultural land? Where else does food come from? (Most of our food comes from agricultural land, but food like fish and shellfish come from water like oceans, rivers, and lakes. Food can also be grown in home gardens and greenhouses.)

     Teach with Clarity As students are thinking about land and its connection to the production of our food, they may wonder about aquatic food sources that do not rely on land. Aquatic food sources include those harvested from the ocean (lobster, salmon, shrimp, shellfish, and some species of fish) and those grown and harvested in freshwater (trout, catfish, and tilapia). Explore FAO's Consumption of Aquatic Foods report to explore foods grown and harvested from the water.

   • What can we learn from this demonstration? (The amount of habitable land where we can live and produce our food is extremely limited. We need to use it wisely and protect it.)

Activity 2: The Value of Topsoil

1. Refer to the apple demonstration from Activity 1. Project the Agricultural Land Apple Slice image. Remind the students that almost all of our food is produced on this relatively small portion of Earth. Ask, "What non-renewable natural resource covers the surface of agricultural land?" (topsoil) The peel of the apple can represent topsoil. For added effect, peel the segments that represent agricultural land in the demonstration.
2. Lead a discussion about the economic, environmental, and societal value of soil. Include the following points and questions in the discussion:
   • Topsoil is what makes agricultural land valuable and capable of growing crops or supporting livestock for our food.
   • Crops grow best in fertile topsoil.
   • Soil is a nonrenewable resource because it can take 100 to 500 years to make one inch of new topsoil.
   • It is important to protect topsoil. Farmers use conservation practices to protect topsoil from erosion.
   • Say you have 1 acre of land and 7 inches of topsoil. If every inch is worth $10 (round numbers simplify the math), your topsoil would be worth $70.
   • Suppose you lose ½ inch of topsoil each year to erosion. How much money would you be losing each year? ($5.00 of topsoil from one acre) What is your topsoil now worth? ($65.00) At your current rate of topsoil loss, how many years will it take to lose all seven inches? (14 years). 
   • Discuss other losses that would occur (crops will be less productive, your income will go down, you will feed fewer people with the crops grown on your acre, sediment will wash into lakes and rivers downstream). How much would you be willing to pay to prevent erosion of your topsoil?
   • Since soils provide our food, how can we place a value on them? Who pays for soil conservation? Who benefits from soil conservation?
   • What is an acre of farmland worth? What is an acre of city worth?