Diagram a feedback cycle (with one or more branches, including + and /or - signs) including at least 4 of the following (and yo

Many possible answers here. Here is one scenario:

+ precipitation clouds

Primary production albedo

+ air temperature

CO2 emissions soil temperature

+ +

soil respiration

NEGATIVE FEEDBACK CYCLE (but not necessary to identify). CO2 emissions cause increased primary production (plants use CO2 for photosynthesis). Primary production produces humidity (via transpiration) and this may cause an increase in local precipitation. More atmospheric moisture will bring clouds, which will increase the albedo of the Earth. Increased albedo will cause decreased air temperatures which will decrease soil temperatures and soil respiration (microbial process of decomposition). Decreased soil respiration will lead to decreased CO2 emissions to the atmosphere.

3). Currently, the land area of Denver covers 397 square km (155 square mi). Rapid development has been increasing the area of the city by 11% per year. Show your work in all parts, below.

a) How long will it take for Denver to double in its land area? (3 pts)

70 divided by 11% = about 6-6.5 years

b) How large will Denver be at this time? Put your answer in "lay person" terms (ex. the state of Delaware is 1955 square miles) (2 pts).

310 square miles, or approximately 1/5 the size of Delaware (actually its 16%)

c) At the same time, the population of an endangered species (for the sake of argument, say the Prebles Meadow Jumping Mouse) is decreasing by 5% per year. How long will it take for this population to become half of its current size? (2 pts)

70/5% = 14 years

d) You have a friend who doesn't understand why people are concerned by a small number like 11% growth. Explain exponential growth to your friend in terms he can understand. If helpful, use analogies, stories or diagrams to get your point across clearly and effectively. (3 pts).

An example: Exponential growth means that a population is growing at an increasing rate over time (number of people/year). With each year, there are more many more people added to the population than the last year. In fact, when the population doubles, more people have been added (in the doubling event) than all the people that previously existed in the population. One grain of wheat on a chess square, doubled for each square, would lead to 2⁶⁴ grains of wheat!

4). Consider the Rocky Mountain subalpine ecosystem where plants take in (and use for growth) 300 g carbon per square meter of land area per year (also written as 300 g C m^-2 y^-1). Within this ecosystem there are 4 trophic levels: grass, rabbits, foxes, and eagles. Hint: Carbon taken in by each trophic level creates the energy for the organism.

a) Draw this trophic system and indicate (using the appropriate units) the production at each level. (3 pts) eagles 0.3 g C m^-2 y^-1

foxes 3 g C m^-2 y^-1

rabbits 30 g C m^-2 y^-1

grass 300 g C m^-2 y^-1

b) Why does this pattern occur? (2 pts)

Because only 10-20% of the energy (or carbon) is passed to the next trophic level due to energy loss between levels. Energy is “lost” from the organism or ecosystem (or in carbon terms, CO2 is lost from the organism or ecosytem) due to increased energy used (respiration) due to foraging, maintenance, or defense.

c) Draw another diagram (no numbers) showing the relative concentrations of DDT (high, medium, low, lowest) at each trophic level if it were sprayed in this ecosystem. Explain your diagram. (3 pts)

eagles HIGH

foxes MEDIUM

rabbits LOW

grass LOWEST

d) Based on your answers above, what are two reasons some people like to eat lower on the food chain? (2 pts)

1. More energy efficient (less energy lost as heat – or carbon lost as CO2)

2. Less likelihood of BIOCONCENTRATION of pesticides and heavy metals.

5). Fossil fuel combustion (power plants, motor vehicles) also produce high concentrations of particulate matter that can be classified as "aerosols" in the troposphere. Aerosols high up in the troposphere can act as cloud condensation nuclei, and clouds (which contain water vapor) are very reflective of the sun's ultraviolet radiation. Aerosols themselves are also very reflective of ultraviolet radiation from the sun.

a) How will high aerosol concentrations in the atmosphere alter the Earth's albedo? (2 pts)

High aerosol concentrations will increase the Earth’s albedo.

b) Using arrows (but no numbers), diagram and explain the energy balance of the earth and atmosphere including both greenhouse gases and aerosols from human activity, with arrows indicating where energy is reflected, absorbed, re-radiated, etc. (5 pts)

UV radiation

GHGs (Troposphere) Aerosols

radiation

Earth

Short-wave (UV) radiation comes in to the Earth’s atmosphere from the sun, is absorbed by the Earth, is transformed into long-wave (IR) radiation, radiates back to the atmosphere, is absorbed and reradiated by GHGs (greenhouse gases such as CO2, H2O, O3, N2O, CH4). Aerosols reflect ultraviolet radiation from the sun back out to space (and thus cool the planet).

b) Carbon dioxide, methane, and nitrous oxide concentrations are increasing in our atmosphere less than 1% per year on average due to human activity. Why are people concerned about this very small number? Explain. (3 pts)

Despite the small % increases, the change in concentrations of these gass is important: These gases are greenhouse gases which have the special ability to absorb and reradiate IR radiation from the Earth. Some of these gases (N2O and CH4) have long lifetimes in the atmosphere and may play a larger role in the greenhouse effect than their small concentration implies. Another reason to be concerned is that these increases are all due to fossil fuel combustion and fertilizd agriculture.

6). You are standing in the produce section of King Soopers contemplating whether or not you will buy unmarked grapes (conventionally farmed) or the more expensive grapes marked "Organic". Your mind runs over both the positive and negative aspects of your decision.

a) Explain what is organic farming, including two examples (3 pts), and then explain at least four reasons why you make the choice that you do (whichever side it is on) (3 pts).

Organic farming is agricultural production without the use of synthetic pesticides or fertilizers (and sometimes no GMOs). Examples of organic farming techniques are: composting food for fertilizer, using natural predators to reduce crop pests.

Buying organic will: decrease fertilizer use and runoff, decrease pesticide use and runoff, increase small-family farming, decrease GHG emissions from agriculture (CO2, N2O), increase carbon sink in soil (no-till organic), among others!

b) Why are organic grapes more expensive? (2 pt)

Organic farming is labor-intensive, and markets for organic produce are currently small (due to lack of public understanding of ecological consequences of agriculture). Small markets = more expense per produce item

c) How might farmers bring down the price of their organic grapes in the future? (2 pt)

Promote organic product consumption, increase total sales, decrease price because of increased efficiency in producing large quantities of a product.

7). A close examination of the human system of food production reveals stunning facts and figures. List and briefly explain (one or two sentences) three facts that you will remember about our current state of food scarcity, land degradation, or use of water, energy, and fertilizer. (10 pts)

Many answers possible here. Check book for details!

8. Are environmental problems caused by human population growth?

a) Explain arguments on both sides of this issue, using examples. Use scientific language and evidence whenever possible. (6 pts).

Yes. People will demand food to survive. Little chance that policy will opt for starving people intentionally. More food production will mean more arable land needed (land-use change) or more intensive agricultural practices (fertilizer, water, pesticides, etc.).

No. Increased national wealth is highly correlated with increased national environmental regulations. Poverty causes high fertility levels (studies show that less education = more babies for women globally) which may then cause environmental degradation.

b) Where on Earth is population growth going to be the largest in this century (2 pts)?

Developing world. (Not US, Canada, Japan, Northern Europe)

c) If so, why should people in the US be concerned? (2 pts)

People in US use 35 times the resources, on average, than people in India! True for much of the developing world. US population growth is relatively small, but we have an insatiable appetite for energy!!

9. What are 10 things that you do in your life that contribute to environmental problems? List the behavior, its ecological consequences, and whether this problem is local, regional, or global. Be scientific and detailed with your language (10 pts).

Many answers will work here. Here are some of mine:

Electricity consumption causes CO2 emissions which is a global problem
Electricity consumption causes NOx emissions which is a local and regional problem
Use of non-biodegradable plastics cause CO2 and hydrocarbon emissions which are global (CO2) and regional (Hydrocarbon) problems
Driving my car increases oil consumption & increased chance of large oil spills which is local problem
I sometimes eat non-organic food which supports pesticide and fertilzer use which may cause runoff to aquatic systems. This is a regional and local problem
I buy products from overseas which (if food-based) may cause fertilizer and pesticide use (and thus runoff), deforestation, or use of endangered species. This is a regional and global problem
I support economic growth in developing countries which will cause increased CO2 emissions (likely). Global problem
I live in a one-story house with only two people total. Increases urban sprawl, which is a local and regional problem.
I use medicines that have been synthesized using petroleum (ultimately). CO2 emissions, global problem
I have a cat, and although she wears a bell she may kill native birds and rodents. Local problem.

100%

Soil

Carbon

g C per

sq. meter 50%

of land area

Time (years) 50 years

10. You are a reporter who is interested in the effects of deforestation on ecosystem functioning. You travel to the Amazon basin and study an area that has been deforested 30 years earlier and is currently used for crops.

a) Draw the graph of soil carbon you expect to see over time, with the deforestation event (30 years earlier) marked by the arrow. Make sure you put years on the X axis (3 pts)

b) Why does this pattern occur? Explain, using scientific and detailed language (3 pts).

Soil carbon is another name for soil organic matter. Organic matter in the soil is caused by plant growth and death. Organic matter is lost from the soil when microbes decompose soil organic matter and turn it into CO2. Following deforestation, plants are burned and cut down. High temperatures and high moisture at the soil surface causes increased decomposition (respiration) of soil carbon. At the same time, plant inputs (from leaves and roots) are decreased due to deforestation and burning.

c) What are the consequences of this pattern for the growth ("health") of these crops? Explain, using two examples. (4 pts)

Soil organic matter is a source of nutrients for plants. Low soil organic matter means low nutrients for plant growth, which means plants will be increasingly dependent on external fertilizer inputs. Examples: Loss of topsoil in developing countries where hillsides are terraced for agriculture, Slash and burn agriculture in Mexico, Southeast Asia.

EXTRA CREDIT (2 pts): (you can answer on back)

Why did we make a big deal about avoiding the words "good" and "bad" at the beginning of this course?

Good and bad are HUMAN-based values. Earth systems are value-neutral. What happens to the Earth is good or bad only in terms of OUR PERCEPTION and VALUES.