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Grade 8 Integrated Science Chapter 20 Lesson 2 on human impact on the land. This lesson is a detailed look into the positive and negative effects of humans to land biomes. This lesson includes topics such as resource management, the nitrogen cycle, deforestation, mining, agriculture, and urban sprawl. Students should consider the many different impacts we have on the environment everyday.
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Chapter 20 Lesson 2P724-731
IMPACTS ON THE LAND
Vocabulary
Deforestation – the removal of large areas of forests for human purposes
Desertification – the development of desert like conditions due to human activities and/or climate change
Urban Sprawl – the development of land for houses and other buildings near a city
Reforestation – planting trees to replace trees that have been cut or burned down
Reclamation – the process of restoring land disturbed by mining
Using Land Resources
Obtaining resources from nature for books, pens, everything requires people to use land for timber production, agriculture, and mining.
All of these activities impact that environment
Forest Resources Trees are cut for fuel and to clear land for
agriculture, grazing, or building houses or highways
Sometimes large portions of forests are cleared
Deforestation is the removal of large areas of forests for human purposes. Approximately 130,000km2 of tropical
rainforests are cut down each year. Tropical rain forests are home to an estimated
50% of all the species on Earth. Deforestation destroys habitats, which can
lead to species’ extinction.
Borneo Deforestation
Forest Resources
Deforestation can also affect soil quality. Plant roots hold soil in place. Without these natural anchors, soil erodes
away. Deforestation can also affect air quality
Trees remove carbon dioxide from the air when they undergo photosynthesis.
With fewer trees more CO2 remains in the air.
Agriculture and the Nitrogen Cycle It takes a lot of food to feed 7 billion people To meet the food demands of the world’s
population, farmer often add fertilizers that contain nitrogen to soil to increase crop yield
Living things must use nitrogen to make proteins
When living things die and decompose they release that nitrogen back into the soil and the atmosphere
Agriculture and the Nitrogen Cycle Although nitrogen gas makes up about 79%
if Earth’s atmosphere, most living things cannot use the gaseous form of nitrogen.
Nitrogen must be converted into a usable form.
Bacteria that live on the roots pf certain plants convert atmospheric N into a form useful for plants.
Fertilizers used today contain a abundant amount of Nitrogen in its usable form
Agriculture and the Nitrogen Cycle Scientists estimate that human activities
such as manufacturing and applying fertilizers to crops have double the amount of nitrogen cycling through ecosystems.
Excess nitrogen can kill plants adapted to low nitrogen levels and affect organisms that depend on those plants for food.
Fertilizers can seep into groundwater supplies, polluting drinking water
They can also run off into streams and rivers, affecting aquatic organisms
Other Effects of Agriculture
Soil erosion can occur when land is overfarmed or overgrazed
High rates of soil erosion can lead to desertification
Desertification is the development of desert-like conditions due to human activities and/or climate change
A region of land that undergoes desertification is no longer useful for food production
Mining
Many useful rocks and mineral are removed from the ground by mining For example, copper is removed from the
surface by digging a strip mine. Coal and other in-ground resources also can be
removed by digging underground mines Mines are essential for obtaining much-
needed resources. However, mines disturb habitats and
change the landscape. Runoff that contains heavy metals can also
pollute water sources if not regulated.
Underground Mining
Construction and Development Land itself is also a very important
resource. People use land for living space.
Urban Sprawl
The development of land for houses and other buildings near a city is called urban sprawl In the 1950s, large tracts of rural land in the US were
developed as suburbs, residential areas on the outside edges of a city.
When the suburbs became more crowded, people moved farther out into the country.
Urban sprawl impacts the environment by habitat destruction and loss of valuable farmland
As more ground is paved for sidewalks and streets, runoff increases because rainwater cannot drain into the soil.
Typically runoff from cities and suburbs contain many pollutants, like sediment and chemicals, which can reduce the water quality in streams, rivers, and groundwater
Roadways
Only a small percentage of Americans owned cars before the 1940s. By 2005, there were 240 million vehicles for
295 million people In 1960, the U.S. had about 16000km of
interstate highways. In 2012, the interstate high system
includes 47000km of paved roadways This, like urban sprawl, also destroys
habitats.
Recreation
People also use land for recreation
Waste Management
Everyday, each person in the U.S. generates about 2.1 kg of trash. That adds up to 230 million metric tons per
year.
Landfills
About 31% of trash in the U.S. is recycled and composted.
About 14% is burned About 55% is places in landfills where trash is
buried
A landfill is carefully designed to meet government regulations. Trash is covered by soil to keep it from blowing
away. Special liners help prevent pollutants from leaking
into soil and groundwater supplies.
Hazardous Waste
Some trash cannot be placed in landfills because it contains harmful substances that can affect soil, air, and water quality.
This trash is called hazardous waste. The substances in hazardous waste can also affect the
health of humans and other living things Both industries and households produce hazardous
waste Medical hazardous waste includes used needles and
bandages Household hazardous water includes used motor oil and
batteries The EPA (U.S. Environmental Protection Agency) work
with state and local agencies to help with safe disposal.
Positive Actions
Human actions can have negative effects on the environment, but they can have positive impacts as well
Governments, society, and individuals can work together to reduce the impact of human activities on land resources.
Protecting the Land
Yellowstone National Park was the first national park in the world, establish in 1872. This set an example to other countries for
setting aside land for preservation State and local governments also followed this
example in the U.S. Protected forests and parks are important
habitats for wildlife and are enjoyed by millions of visitors each year Mining and logging are allowed on some of
these lands However, the removal of resources must meet
environmental regulations
Reforestation and Reclamation A forest is a complex ecosystem,
With careful planning, it can be managed as a renewable resource.
For example, trees can be select-cut That means that only some trees in one area are
cut down, rather than the entire forest. People also can practice reforestation
Reforestation involves planting trees to replace trees that have been cut or burned down
Reforestation can keep a forest healthy or help reestablish a deforested area.
Reforestation and Reclamation Mined land also can be made
environmentally healthy through reclamation. Reclamation is the process of restoring
land disturbed by mining. This happens by reshaping the area,
covering it with soil, and replanting trees and other vegetation.
Green Spaces
Many cities use green spaces to create natural environments in urban settings.
Green spaces are areas that are left undeveloped or lightly developed. They include parks within cities and forests
around suburbs Green spaces provide recreational
opportunities for people and shelter for wildlife
They also reduce runoff and improve air quality as plants remove excess CO2 from the air
How can you help?
Individuals can have a big-impact on land use issues by practicing the 3-Rs. Reusing is using an item for a new purpose Reducing is using fewer resources Recycling is making new products from a used
product Composting also lessens land impact
You can compost food scraps into a material that is added to soil to increase its fertility
Compost is a mixture of decaying organic matter that improves soil quality by adding nutrients.