How Do Humans Impact
Their Environment?
Water Diversion/Management
• Humans need water to live and grow food.
Humans have invented several ways for
managing water supplies such as building
reservoirs and canals for irrigating crops
and ensuring a constant supply of water.
Examples
• The Aral Sea
• Colorado River
The Aral Sea
• The Aral Sea is located in Central Asia
between Kazakhstan and Uzbekistan. Since
the 1960s it has been shrinking due to over
irrigation. It is now 20% of its original size.
The Soviets used the diverted water to
irrigate cotton fields.
The Aral Sea
The shrinking of the Aral Sea has caused:
A. The collapse of the local fishing industry.
B. Increase in respiratory illnesses due to
wind stirring up dust of exposed seabed.
C. Extinction of plants and animals.
The Aral Sea
The Aral Sea
The Colorado River
• The Colorado River is an excellent example of
how humans can impact the environment
through irrigation. The River starts in Colorado
and empties into the Gulf of California. On every
stretch of the river farmers take water to irrigate
crops. People have also built several dams on the
river, the most famous is the Hoover Dam.
Changing Landscapes
• Humans change the landscape of the earth
in order to farm or raise animals.
Examples
• Agricultural Terracing
• Deforestation
• Desertification
Agricultural Terracing
• People practice agricultural terracing in
mountainous areas in order to make flat
land to farm on.
Think!
• Look at a map and try to think of some
countries or areas where people may
practice agricultural terracing.
A. The Andes Mountains in South America
B. The Himalaya Mountains in Asia
Agricultural Terraces in Peru
Cultivation of Rice in Terraces in China
Deforestation
• Deforestation is when humans cut down
trees faster than they can grow back.
Deforestation
• A few causes of deforestation are:
A. Forest land is cleared for farming or
human settlement.
B. Forests are cut down and the timber is
sold.
C. Slash and burn farming in tropical areas.
Deforestation
• Much of the world has been deforested
including Europe and many parts of the
United States. Areas that are becoming
rapidly deforested right now are mainly
rainforests such as the Amazon Rainforest
in Brazil.
Desertification
• Desertification is an expansion of arid
conditions into a non-arid environment.
Basically, desertification is when a desert
gets bigger due to natural and human
causes.
Desertification
• The fringes of deserts are very fragile
environments. If there is a long period of
no rain such as a drought this area may
turn into a desert. People can also cause
desertification by cutting down trees near
deserts or herding animals such as cattle,
sheep, and goats.
Pollution
• Humans cause air, water, and soil pollution
that harm the environment.
Air Pollution
• Air pollution is mostly caused by the
burning of fossil fuels; oil, coal, and natural
gas. Areas with many coal burning power
plants, factories, and cars can experience
acid rain.
Acid Rain
• A few areas that have acid rain are the
Northeast United States and Canada, the
Black Forest region in Germany, and China.
Acid rain can kill vegetation and fish in
streams and lakes over a period of time.
Water Pollution
• Water pollution is caused by:
A. Runoff that contains pesticides and
fertilizers
B. Waste from heavy industry that contains
metals and chemicals
C. Raw sewage
D. Oil spills and waste from ships