Human Impact on the Lithosphere

Why is the lithosphere important? Provides land/space on which to live Provides necessary resources required for survival, like food and fuel

3 major practices that affect quality of lithosphere Deforestation for energy resources Agriculture Money crops such as tobacco and cotton Food crops such as corn and wheat Urbanization- cutting down trees and clearing land to build homes

How Land Use Has Changed… Over the past hundreds of years, our use of the land has changed drastically We have changed from a largely rural to more agriculture based, and from there to more industry based

Human Impact In the past, soil eroded more slowly Land was covered by more trees and vegetation Human activities like deforestation, agriculture, and urbanization remove vegetation have greatly increased the rate at which erosion occurs

Deforestation Space is needed for agriculture and timber is used for home construction Results in more erosion and rainforests being destroyed Removing plants increases the rate of erosion, because the plant roots no longer secure the soil in one place

AGRICULTURE In addition to losing soil by deforestation, we also lose tons of topsoil each year through agriculture Topsoil is the upper, outermost layer of soil, usually the top 2 inches. It has the highest amount of organic matter and microorganisms, and is where plants obtain most of their nutrients

agriculture Traditional agriculture techniques, like plowing, remove topsoil and require replanting each year. The United States alone loses almost 3 tons of topsoil per acre per year.

Sustainable agriculture Preserving fertile topsoil is essential to feeding the world’s rapidly growing population. This can be done through: (1) Windbreaks (2) Terracing hillsides (3) Contour plowing (4) Crop rotation

WINDBREAKS Windbreaks are located along crop field borders or within the field itself Reduce topsoil erosion by planting trees that block heavy winds

TERRACING HILLSIDES Terracing is the building of wide flat rows of terraces on mountainside and hillsides. The terraces look like big staircases. They hold rainwater so that it will not wash away the soil.

CONTOUR PLOWING Instead of plowing up and down, farmers plow across a slope. In this way, the soil forms a ridge that slows down the flow of water, so soil is not carried away.

CROP ROTATION Crop rotation is the practice of growing a series of different types of crops in the same area in back to back seasons. Improve soil fertility by alternating deep rooted and shallow rooted plants

Effect of development on shoreline Construction along the shoreline increases the rate of erosion beyond the already high rate of erosion experienced along shorelines due to the ocean.

Artificial stabilization: Shoreline structures Structures can be built to protect a coast from erosion or to prevent movement of sand along a beach: Groins Breakwaters Seawalls

Artificial stabilization: groins Groins are barriers built at right angles to the beach to trap sand that is moving parallel to the shore. Groins are built to maintain or widen beaches that are losing sand.

Artificial stabilization: breakwaters Breakwaters are built parallel to the shoreline off the coast to limit the force of oncoming waves. These structures also protect boats from large breaking waves.

Artificial stabilization: SEAWALLS Structure designed to prevent impact of tides and waves on property, built directly along the shoreline.

Artificial stabilization: SEAWALLS Built along the coast to prevent erosion and replace shoreline

Artificial stabilization: beach nourishment Beach nourishment projects add large quantities of sand to the beach. It is an attempt to stabilize shorelines without adding protective features.

Beach nourishment: disadvantages Temporary fix: waves will eventually erode the replacement sand as well Expensive: costs lots of money to transport sand to the beach from offshore areas Negative effects on marine life: dredging sand off the coast replaces natural, coarse sand with softer, muddier sand that increases the cloudiness (turbidity) of the water and can kill offshore coral reefs

Effect of development on mountainsides Construction along mountainsides can decrease the stability of the land, allowing for a greater rate of erosion. Mass movements (ex: rockslides) are more probable.

Artificial stabilization: slope revetment Screen mesh (called slope revetment) draped over a steep slope keeps loosened rocks from entering roadways.

Artificial stabilization: retaining walls Human activities or natural processes can remove some soil from the base of a slope, making the remaining upper part of the slope less stable and more prone to mass movement.  Construction of a retaining wall can support the upper part of a slope.

Artificial stabilization: slope vegetation While harvesting trees, leave enough mature trees to anchor the slope and protect soil from excessive erosion due to runoff.