Human Impact on Ecosystems

BENCHMARK

SC.912.L.17.20 Predict the impact of individuals on environmental systems and examine how human lifestyles affect sustainability.

STATION 1: BiodiversityHow does biodiversity

affect a population exposed to

disease?

VIDEO: The Biodiversity Code

BACKGROUND INFORMATION

When scientists speak of the variety of organisms (and their genes) in an ecosystem, they refer to it as biodiversity. A biologically diverse ecosystem, such as an old growth forest or tropical rain forest, is healthy, complex and stable. Nature tends to increase diversity through the process of succession.

The opposite of biodiversity is referred to as monoculture, or the growing of one species of organism, such as a lawn, a wheat field or corn field. Because all of the species are identical, there are few complex food webs and disease can spread quickly. Monoculture is like a banquet table for disease organisms. Monoculture often requires extensive use of pesticides and herbicides (to fight nature's tendency to diversify communities) and is very labor and energy intensive (fighting nature is tough). Humans often try to reduce diversity because it is easier to harvest a crop (whether it is wheat, corn, a lawn or a secondary forest) if it all contains the same species, but this obviously creates serious problems.

When a habitat is very diverse with a variety of different species, it is much healthier and more stable. One of the reasons for this is that disease doesn’t spread as easily in a diverse community. If one species gets a disease, others of its kind are far enough away (due to the variety of other organisms) that disease is often stopped at the one or two individuals.

“Biodiversity, the planet’s most valuable resource, is on loan to us from our children.”- Edward O. Wilson

DATA:22 students Simulation #1

(Low Diversity)Simulation #2

(High Diversity)

Number of Students Standing

0 21

PROCEDURE:

ANALYSIS:1. Why didn't the disease spread as fast among the Douglas Firs in

Simulation #2 as it did in Simulation #1?

2. In which forest would you need to use more chemicals to control disease: the Douglas Fir forest or the more diversified, old growth forest? Why?

3. Summarize what this simulation symbolized.

4. Which forest would have more diversity of wildlife? Why?

5. If you cut down the variety in a piece of forest you owned and replanted with one type of tree, what will happen to much of the wildlife that was adapted to the forest? (Hint: they cannot just move elsewhere. If other habitats are good, they will probably be near carrying capacity already.)

6. Will this fate happen to all the wildlife? Explain.

STATION 2: Biomagnification

How do chemicals

move through a

food chain?

Background Information:DDT is a pesticide that was used heavily in World War 2 to control mosquito population and reduce the spread of malaria. After the war it was used heavily on crops to protect them from insects. It was not until the 1960s that global problems with DDT became obvious. If DDT is sprayed near an aquatic ecosystem some of it may be taken by small water plants. Small insects will feed off of these plants and accumulate DDT in their bodies. Small fish eat these insects and accumulate higher levels of DDT in their bodies. These small fish may be eaten by birds, bigger fish or any other animal including humans. Rachel Carson wrote the book Silent Spring (1962). This book described a world with out song birds, and got the attention of a lot of people. DDT is not lethal to all organisms, but has many non-lethal effects. One of these is the thinning of shells of carnivorous birds. The shells become too weak and are broken before the bird has devolved. This was the cause of the near extinction of the Peregrine Falcon.

PROCEDURE:

DATA:# organisms # pennies % concentration

Plankton 8 8 1%

Small fish 4 8 2%

Large fish 2 8 4%

Eagle 1 8 8%

VIDEO: Biomagnification

ANALYSIS:1. Using your understanding of the

prefix bio and the root magnify, dissect the word “biomagnify” and explain what you think it means? (your own words)

2. Now, using your book, what does the word biomagnify mean (also known as biological magnification)?

3. How did this demonstration illustrate the process of biomagnification?

4. According to the graph, which trophic level will have the most DDT (a chemical pesticide)?

STATION 3: Cookie Mining

What are the impacts of mining on

ecosystems?

Background Information:As recently as 200-300 years ago humans met most of their energy needs using renewable energy sources such as wood for heat, watermills for grinding crops or wind to propel sailing vessels. Fossil fuels such as oil, gas and coal now provide the majority of the energy we use to fuel our modern technological and industrial based societies.

In the past coal has been used to power steamships and railroad engines, to heat homes and provide heat for steel production. Today the primary use for coal is in the generation of electrical power. More than half the electricity generated in the United States comes from combusting coal and Missouri gets more than eighty percent of its electricity by burning coal.

Coal generates more environmental impacts than any other energy source. Coal mining disturbs large areas of land creating surface water quality problems and ecosystem impacts. Burning coal produces large amounts of air pollutants that have been linked to mercury contamination, smog, global warming and other environmental problems. High sulfur coals are especially problematic, creating greater levels of air pollution and problems with acid rain. Although Missouri has deposits of coal, the high sulfur content prevents its use as an energy source.

Of all the fossil fuels by far the most abundant is coal. North American coal beds are widely distributed (see map) with significant variation in the quality of the coal and its accessibility. Estimating the exact amount of coal available and how long such reserves will last is difficult. Factors such as the current rates of consumption, the expense of mining in remote areas along with increasing environmental costs must all be considered. The United States is estimated to have enough low sulfur coal to last at least 100-200 years.

The world will not only require energy in the future, but those energy needs are predicted to grow. We will most certainly eventually run out of fossil fuels and the development of renewable energy systems such as hydroelectric, geothermal, wind and solar will only become more critical.

VIDEO: Coal Mining

PROCEDURES:1. Distribute the cookies to the students (but they must not eat them!). Explain that the

cookies represent the land and the chocolate chips represent an ore, like coal, which they will be mining from the cookie.

2. With the cookie flat on the desk, and without picking it up, ask students to estimate the number of chips in their cookie.

3. Distribute a copy of the Mining Area Grid to the students. Explain that the images on the grid represent various attributes of the environment where they’ll be mining. Students should place their cookie on the grid and, using a pencil, trace the outline of the cookie.

4. With their toothpicks, students will attempt to extract the chips from the cookie. Cookies should stay flat on the paper (in the real world, you can’t pick up the earth and dig from the bottom!). After a few minutes of mining, ask students if they wish to change their estimate of how many chips are in their cookies.

5. After students have finished mining their cookies, have everyone outline the area on their grid paper that is covered by cookie crumbs. A rough estimate is fine; this doesn’t need to be exact.

DATA:Income Cost

# of Chips minedMoney earned

# of chips X $200

# of crumbs on plate(count # squares

affected)

Cost to repair land # of crumbs X $100

     

     

Money earned from mining

chipsMINUS

Money spent on fixing land damaged in mining

EQUALSTotal Money Earned

Mining

     

  - 

     =

 

ANALYSIS:

1. What was your reasoning for the cookie’s placement, did you consider what natural attributes you’d be covering?

2. Think about how your cookie looked after you finished mining. How does this relate to environmental impacts associated with real coal mining?

3. Were you able to remove all the chips from the cookie? If no, why not?

4. Compare this activity with the real impact when mining coal. What happens to plants and animals?

5. In real mining, why are some deposits of coal more expensive to mine than others?

6. Why is it difficult to predict exactly how long the fossil fuels in the earth will last?

ARTICLE: