Authentic Situation
Beavers are ecosystem engineers. Below, a wildlife manager releases a beaver at a river site. In recent years, scientists and land managers have introduced beaver into river ecosystems with significant damage, such as erosion or vegetation loss. The second image shows a river site with damage, and subsequent habitat improvement possible because of beaver introduction.
Image by USDA; https://www.fs.usda.gov/features/working-beavers-restore-watersheds; public domain
Image by USDA: https://www.nrcs.usda.gov/wps/portal/nrcs/main/national/water/manage/restoration/; public domain
Observations and Wonderings
Focus Questions: Give your best response prior to learning about this topic. Your initial answers may change as you explore this unit.
Bio.1.5 Human Impact
This is an engineering standard. Refer to page 10 to read about engineering design. Which type of engineering task is utilized in this SEEd Standard?
In this section, you will be learning about how human activities affect ecosystems and biodiversity. You will also be learning about some possible solutions. Think about how human activities are affecting ecosystems, and how realistic and effective different solutions for mitigating the effects are.
Water Pollution
Do you live near water? Do you see pollution?
Water pollution is a worldwide problem. Almost anything released into the air or onto the land can end up in Earth’s water.
Water pollution may come from one source. For example, chemicals from a factory may empty into a stream. Water pollution may come from more than one source, too. For example, chemicals may rain from the air into that same stream. It is much more difficult to control pollution from more than one source.
In the developed nations there are three main sources of water pollution:
Agriculture
Chemicals that are applied to farm fields include fertilizers and pesticides. Excess chemicals can be picked up by rainwater. The chemicals can end up in streams, ponds, lakes, or the ocean. Dissolved fertilizer causes tremendous numbers of water plants and algae to grow. This can lead to dead zones where nothing can live in lakes or the coastal oceans.
Waste from livestock can also pollute water. The waste contains pathogens that can cause diseases. Many farms in the U.S. have thousands of animals. These farms produce millions of gallons of waste. The waste is stored in huge lagoons, like the one pictured below. Many leaks from these lagoons have occurred.
This is a pond of hog manure. Check out the vehicles at the bottom of the picture for scale.
Industry
Factories and power plants may pollute water with harmful substances.
Municipal
“Municipal” refers to the community. Households and businesses in a community can pollute the water supply. Municipal pollution comes from sewage, storm drains, septic tanks, boats, and runoff from yards. For example:
What are some solutions to water pollution? Inventor Adam Katzman is using natural processes to treat sewage.
Habitat Destruction
What’s happening to this land?
This picture, taken in southern Mexico, shows land being cleared for agriculture. The forest has been cut down and burned to make room for a farm. In the process, homes to many plants and animals were destroyed. This is an example of habitat destruction.
From a human point of view, a habitat is where you live, go to school, and go to have fun. Your habitat can be altered, and you can easily adapt. Most people live in a few different places and go to a number of different schools throughout their life. But a plant or animal may not be able to adapt to a changed habitat. A habitat is the natural home or environment of an organism. Humans often destroy the habitats of other organisms. Habitat destruction can cause the extinction of
species. Extinction is the complete disappearance of a species. Once a species is extinct, it can never recover. Some ways humans cause habitat destruction are by clearing land and by introducing non-native species of plants and animals.
Land Loss
Clearing land for agriculture and development is a major cause of habitat destruction. Within the past
100 years, the amount of total land used for agriculture has almost doubled. Land used for grazing cattle has more than doubled. Agriculture alone has cost the United States half of its wetlands and almost all of its tallgrass prairies. Native prairie ecosystems, with their thick fertile soils, deep-rooted grasses, diversity of colorful flowers, burrowing prairie dogs, and herds of bison and other animals, have virtually disappeared.
The Flint Hills contain some of the largest remnants of tallgrass prairie habitat remaining in North America.
Slash-and-Burn Agriculture
Other habitats that are being rapidly destroyed are forests, especially tropical rainforests. The largest cause of deforestation today is slash-and-burn agriculture . This means that when people want to turn a forest into a farm, they cut down all of the trees and then burn the remainder of the forest. This technique is used by over 200 million people in tropical forests throughout the world.
As a consequence of slash-and-burn
agriculture, nutrients are quickly lost from the soil. This often results in people
abandoning the land within a few years. Then the top soil erodes and desertification can follow. Desertification turns forest into a desert, where it is difficult for plants to grow. Half of the Earth’s mature tropical forests are gone. At current rates of deforestation, all tropical forests will be gone by the year 2090.
What are some ways that we could either reduce the amount of habitat that is destroyed, or mitigate the effects of habitat destruction on other species? Scientists and engineers are developing ways to use resources more sustainably.
Oil Spills
Can you see the oil in a big oil spill?
Of course. The photo on the left shows the Gulf of Mexico oil spill after oil has leaked for nearly one month. About a month later, about twice as much oil was spilled into the Gulf, as seen on the right. The water moves and so the oil moves with it.
Oil rigs are built in the oceans to get at oil buried beneath the seafloor. These rigs
pump oil from beneath the ocean floor. Huge ocean tankers carry oil around the world. If something goes wrong with a rig or a tanker, millions of barrels of oil may end up in the water. The oil may coat and kill ocean animals. Some of the oil will wash ashore. This oil may destroy coastal wetlands and ruin beaches.
New drilling techniques allow oil companies to drill in deeper waters than ever before. In April 2010 a rig in the Gulf of Mexico exploded. Eleven workers were killed and 17 injured. When the drill rig sank, a pipe was disconnected and oil gushed into the Gulf. Three months later the well was capped. But 4.9 million barrels had entered the Gulf, about 16 times more oil than the largest oil spill to date.
Cleanup
Once the oil is in the water, there are three ways to try to clean it:
The total effect of the oil spill on the environment of the Gulf is not yet known. Oil is found in the sediments on the seafloor. Many people who fish or are involved in Gulf tourism were also impacted. Studies of the effects of the oil spill on people and animals will continue for many years.
Mining
Can you tell that this was mine?
Mining can do a lot of damage to a region. Mining companies are now supposed to return the land to its natural state when they are done. Sometimes this works really well. It’s hard to tell there was a mine here!
Mining provides people with many resources they need. But mining can be hazardous to the environment. For surface mines, miners clear the
land of soil and plants. Nearby lakes and streams may be inundated with
sediment. The mined rock may include heavy metals. These also enter the sediment and water. Removing metals from rock may involve toxic chemicals. Acid flow from a mine site will change the chemistry of a nearby stream or lake.
Mine Pollution
Mining can cause pollution. Chemicals released from mining can contaminate nearby water sources. Pictured below is water that is contaminated from a nearby mine. The United States government has mining standards to protect water quality.
This water has been polluted by a mountaintop removal mine.
Land Reclamation
One way that scientists and engineers
have tried to mitigate the effects of mining is to reclaim the land. U.S. law states that once mining is complete, the land must be restored to its natural state. This process is called reclamation. A pit may be refilled with dirt. It may be filled with water to create a lake. The pits may be turned into landfills. Underground mines may be sealed off or left open as homes for bats. The land is reshaped. Native plants are planted.
Putting It Together
Image by USDA; https://www.fs.usda.gov/features/working-beavers-restore-watersheds; public domain
Focus Questions
Final Project
We have been exploring how engineers and biologists are using beavers to restore damaged river ecosystems. Now come up with another environmental problem created by human impact. Make a powerpoint that covers the following:
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