1. Engage students’ interest in learning about agricultural production.

Show the Yields of Cereal Grains from 1961 to 2012 graph image. (Download the image from the media carousel above by clicking on the down arrow in the lower right corner of the carousel window.) Tell students that agricultural yields have increased over the past 50 years. Ask:

• Which area has the highest agricultural production of cereal grains? (North America has the highest yields of cereal grains.)

• Why do you think there are occasional dips in crop yields? (Answers will vary. Yields could drop because the weather was not cooperative or because there were pest infestations.)

Tell students they will explore the factors that led to increased crop yields and be asked to predict whether these increases can continue in the future.

2. Discuss the role of uncertainty in the scientific process.

Tell students that science is a process of learning how the world works and that scientists do not know the “right” answers when they start to investigate a question. Tell students that they can see examples of scientists' uncertainty in forecasting crop yields. Show the Projection of Maize Crop Yields in France graphs. (Download the image by clicking on the down arrow in the lower right corner of the media carousel window.) Tell students that these graphs show the average daily precipitation, number of hot days, and yield of maize. The gray line shows the predictions for crop yield based on technological improvements. The pink shading shows the expected yield based on temperature and precipitation influences. The red lines outside the pink shading show the total uncertainty. Ask:

• Does the technology trend (gray line) accurately predict crop yields? (No, the technology trend does not adequately predict crop yields. This is because crop yields are dependent on temperature and precipitation as well as technological improvements.)

• Why do you think the crop models still have uncertainty even after accounting for precipitation and temperature differences year to year? (Student answers will vary. The crop yield could be affected by a pest infestation.)

Tell students they will be asked questions about the certainty of their predictions. Let students know that they should think about what scientific data is available as they assess their certainty with their answers. Encourage them to discuss the scientific evidence with each other to better assess their level of certainty with their predictions.

3. Introduce the concept of stocks and flows in a system.

Tell students that materials flow into and out of systems. The flow of the materials over time can change and can be influenced by many different factors and interacting parts.

Scientists think about how one part of the system can affect other parts of the system. Give students a simple example of a stock and flow in a system, as described in the scenario below.

There is a bathtub with water flowing in from the faucet and water leaving through the drain. Ask:

• When the drain is plugged, what happens to the level of water in the bathtub? (The water level will increase because the outflow of water is stopped, but water keeps coming in from the faucet.)

• When the faucet is turned off, what happens to the level of water in the bathtub? (The water level will decrease because the inflow of water is stopped, but the water keeps leaving through the drain.)

• How can the level of water in the bathtub be kept at the same level? (The water in the bathtub can be kept at the same level by making the inflow equal to the outflow. Then the water that comes in through the faucet will be offset by the water that leaves through the drain.)

4. Have students launch the Best Practices interactive.

Provide students with the link to the Best Practices interactive. Divide students into groups of two or three, with two being the ideal grouping to allow groups to share a computer workstation. Tell students they will be working through a series of pages of questions related to the data in the interactive. Ask students to work through the interactive in their groups, discussing and responding to questions as they go.

NOTE: You can access the Answer Key for students' questions—and save students' data for online grading—through a free registration on the High-Adventure Science portal page.

Tell students this is Activity 6 of the Can We Feed the Growing Population? lesson.

5. Discuss the issues.

After students have completed the activity, bring the groups back together and lead a discussion focusing on these questions:

• What techniques have been used to increase crop yields around the world? (Different ways of planting crops have increased the yield of rice, as in the System of Rice Intensification project. Scientists have been able to crossbreed crops to create better-yielding crops, and genetic modifications have allowed some crops to be grown without using pesticides. Scientists have developed fertilizers that can help crops grow to their full potential. Farmers use irrigation during dry years to provide enough moisture to their crops.)

• What is the relationship between monocropping and pesticide usage? (When crops are monocropped [a single crop being grown year after year in the same fields] pesticide usage can be high. This is because the pests have a lot of access to a single crop. When the crops are rotated or smaller fields are planted with different crops, the amount of food available to a specific pest is limited. With large fields of the same crop, pests have a feast. To limit the damage caused by pests, pesticides might need to be applied more than they would be in smaller fields with different types of crops.)

• Do you think agricultural production will continue to increase? (Answers will vary. There are many challenges facing agriculture today. Much of the increased yield is due to modern technology, but there may be limits to how much technology can continue to increase crop yields. The technology used in North America might not be applicable to agricultural areas of other regions of the world.)

• Why won't a land management plan from one field be just as good for another field? (Land management plans should differ for different fields because they should be suited to the land, not a one-size-fits-all solution. A field on a hill will need to be planted differently than a flat field. Fields in a very rainy or windy climate will need to be treated differently than fields in drier, less windy climates. The land management plan should focus on preserving the soil and increasing its quality. This means the first focus should be on preventing erosion. The next focus should be on putting more organic material into the soil so it can hold more moisture and be more nutrient-rich. This can be done with different tillage strategies and crop rotation.)