Transcript Humans Impacts on Land
Humans Impacts on Land
Objective 2.07
Discuss and analyze how humans influence erosion and deposition in local communities, including school grounds, as a result of: Clearing land. Planting vegetation. Building dams.
• Humans affect weathering and erosion by their activities on the planet. Almost every human activity changes the Earth’s surface. Change occurs as humans convert land for human use. • Along with disturbing plants and animals, urbanization disturbs the soil and vegetation in the area. This can alter the water cycle by changing the way water moves in the area. Changing large areas of land quickly can harm the environment. We must find ways to reduce our impact on the environment.
Clearing Land
• There many ways humans clear land.
Logging
the cutting of trees. Humans use trees for many reasons, like building and paper-making. Sometimes the easiest method of logging is to is
clear-cut
the area. This means to cut down all the trees standing in an area. The impact of clear cutting can be huge! It changes large areas of land by reducing the number of trees in an area. Without tree roots to hold down the soil, rain washes the soil away. This makes the land more barren. Clear cutting causes soil erosion on a large scale.
•
Deforestation
is the removal of trees in a forest. It converts a forested area into non-forested land. Forests can disappear naturally by forest fires or other natural disasters. However, humans cause most deforestation. Humans remove forests to use the land for different reasons. Agriculture, urban building and wasteland are a few examples. Deforestation severely reduces the number and variety of plants in the area. This destroys forest habitats. Deforestation also increases soil erosion and the risk of flooding. In these ways, deforestation can be very damaging to the environment.
•
Aerial View of Sediment Run-off Caused by Massive Amazon Deforestation. This entire area has been stripped bare of forest, so there are no longer any plants, bushes or tree roots to hold soil...which runs off into rivers and streams, killing marine life, even after the animals on land have been killed due to deforestation.
Planting Vegetation
• When humans remove vegetation, soil erodes quickly. The loss of vegetation weathers and weakens the soil. Weathered soil is at greater risk of erosion by natural causes too Natural disasters like landslides and flooding are more likely to occur. Humans can reverse any negative effects they have on the environment by planting vegetation. Planting in cleared areas reduces erosion. It helps restore the soil back to health.
• Planting trees reverses the effects of deforestation.
Reforestation
is the replanting of native tree species in deforested regions. Planting trees repairs the soil. It restores the forest’s natural habitat. This increases the overall health of the forest. Reforestation can happen naturally if the area is left undisturbed for a long time. Since humans are the main cause of deforestation, it is important for us to restore forests. Trees are an important natural resource. We use trees for building and making products. As we cut trees down, we must replant them. This will ensure their supply in the future.
Building Dams
• Humans build dams to either control the flow of water or stop it. Dams are structures built across a body of water, such as a river. They slow the movement of water behind the dam. This causes the river to deposit sediment that it was carrying. Dams also create large reservoirs where the water is stopped. This becomes an important supply of water for human use. Dams contain the flow of water and decrease erosion. Since water is contained, dams also decrease risks of flooding.
• Dams are built for other reasons too. They are sometimes built to generate power. As water moves through a damn, the water turns the turbines of an electric generator. (Recall that moving water is very powerful!) These types of dams are hydroelectric power plants.
Hydroelectric
means that the electricity is generated by the movement of the water.
Minimizing Human Effects
• Humans often clear land for development. You probably seen a construction site while walking down the street or riding in a car. Large tracks and machinery dig up the ground. They carry large piles of soil away. Each building project alters the land in a particular way. But, all construction changes the land in a similar way: by removing trees, plants and soil from the construction site. The result is an increase in soil erosion. Humans have designed ways to reduce erosion while building. Most urban areas require that sandbags and nylon fencing surround construction sites. These reduce the loss of soil by runoff and lessen the amount of soil washed into storm drains. Once construction is complete, vegetation is replaced. This reduces soil erosion back to normal levels.
•
Farming
involves planting and growing crops. Farming requires the use of large tracts of land. It requires digging up and tilling (turning over) soil. Farmers must make a commitment to
sustainable
practices. This means farming in a way that reduces the impact on the environment. It is important for farmers to reduce water runoff and soil erosion. This helps maintain soil quality. This , in turn, keeps crop yields high, a benefit to all.
• Many farmlands are surrounded by stands of tall trees. The trees prevent winds from carrying off too much topsoil. They are called grown on the flat part of the step. loss.
windbreaks
is made into step-like formations. Crops are slow the flow of water downhill and lessens water runoff. This protects the topsoil. . In hilly areas, the soil is terraced. This means it
Soil terracing Irrigation
is the watering of soil when it is dry. This may be done during periods of dry weather. Because the soil is dry, water applied to the soil can be lost by erosion or evaporation. Irrigation of farmland must be done carefully to minimize any water
These books are missing from our classroom.
Has anyone seen these?