Land Use Lesson 8 : Investigating Land Use, Water, and Air Relationships
Use of graphic information and analysis of data in pictorial form are successful pedagogies with most students. Posters are one means of presenting graphic information. Posters are a good way to stimulate discussion, since nearly all students can recognize and interpret the pictorial information. A Michigan’s Land, Air, and Water poster showing how the three elements are linked with hands-on decision making is the basis for this lesson.
Human activities and physical characteristics of a landscape influence the type of land use that can/ may occur. In turn, specific land uses affect water quality. For example, a natural prairie will have grasses and flowers covering the entire piece of land. Because of the thick vegetative cover, only a small amount of soil will erode and be deposited into a nearby stream, river, or other body of water. This will promote the quality of the water in the region. A sand dune, on the other hand, contains less vegetation than a prairie. More soil (sand) is exposed to water and wind. A much greater amount of soil is eroded from surfaces that lack vegetation. The erosion affects the quality of water, which becomes brown with silt and soil. Erosion also loads streams and lakes with sediment. This is an example of where land use has had a negative effect upon water quality.
In some areas of Michigan, sand mining is a land use, the sand is used for metal castings and glass making. A more common mining operation that occurs in nearly every Michigan county is gravel mining (gravel pits). The gravel is extracted, processed, and used for many things, including road beds, concrete sidewalks and streets, landscaping around buildings, and keeps double-bottom gravel trucks busy. Mining is one of the land uses that affects water quality since open pit mines collect water that may become polluted. Mining operations also may produce large quantities of dust, which affects air quality. As students travel and observe in the local community, they will see examples of land uses that affect water and air quality. The intent of this activity is to observe and suggest what those relationships could be based upon the poster they will be using.
Pollutants used and produced with different land uses can also affect air and water quality. These pollutants often move into water bodies through soil infiltration and runoff. Water pollution is often the result of runoff from parking lots, where cars drip small amounts of oil, gasoline, and grease onto the surface. While nearly imperceptible to people, these pollutants are carried by water from the parking lot into a nearby storm sewer system, which may then discharge into a stream, lake, or ocean. When this occurs from many parking lots such as from several shopping malls, the pollutants are accumulated and have detrimental effects on water quality. This is an example where land use and water quality are very closely related.
Air quality is also decreased when more soil is exposed. Wind can pick up soil particles and can carry them long distances. The stronger the wind, the more soil that is carried into the air and the worse air quality becomes. Air carries many pollutants, such as soot, ozone, carbon monoxide, and industrial and transportation by-products. The particles of pollution in the air gradually settle to the surface of Earth under the force of gravity. The pollutants are somewhat like the dirt that settles in students’ homes and is then vacuumed into the bag. The dirt settles to the bottom of the bag due to the force of gravity when the vacuum is turned off.
The study of land use, air, and water is a good way for students to follow a pollutant through the three systems. For example, a pollutant that arrives by air, such as acid rain, falls on the ground from the air and soaks into the land. When the land dries, the acid may remain. As more rain falls later, the accumulated acidified soil releases the element to small streams of water that carry the acid into lakes and rivers. Some soils neutralize acid rain, so local land conditions are important to know about in each case. For this lesson, those details of science are not the focus. Some basic information follows that may be helpful.
The sandy soil that comprises Michigan’s land surface originated from two different sources: granite and limestone. Each type of rock breaks down into sand with a distinct color difference. Granitic sand is dark in color; limestone sand is light in color. The beaches and dune fields of coastal Michigan are lightly colored, indicating a limestone origin. In much of Michigan, the soil is composed largely of weathered limestone. Limestone is a base and neutralizes the acid rain. However, in some regions of Michigan the granite bedrock is at the surface. In those regions the acid is carried to local lakes and streams.
The application of pesticides and herbicides on farmland are pollutants that the student can trace through the land, air, and water connections. Discuss the idea that what goes in the air and on land nearly always ends up in the water.
A jigsaw procedure is used to combine students into new grouping so that the expertise with each part of the poster is brought to each new group. For example, round 1 is a pair of students working on one part of the poster; round 2 of the jigsaw has pairs of students from one part of the poster combine with pairs of students with other parts of the poster so that a larger group of six students has the entire poster. This lesson includes a scoring guide for assessing small group discussions. If it is used, the teacher should review the performance criteria with students that are judged to be important.