Global Carbon Cycle and Global Warming

Human activity, including burning fossil fuels, deforestation, and buring trees, has altered the global carbon cycle. Carbon dioxide is an example of a greenhouse gas. (Greenhouse gas- http://www.eoearth.org/article/Greenhouse_gas). Thus, if the concentration of carbon dioxide has increased and carbon dioxide is a greenhouse gas, then we might predict that global temperatures should be increasing. Thus alternation of the global carbon cycle is the proposed cause of global climate change (global warming). Although global warming is not a focal point of this course, I think that it is important that you are able to address this issue intelligently with your students. Here is some info that you might find useful

Obviously, global climate change is a very imporant issue facing us today. If you are alive and paying any attention, then you probably know that there is some disgreement out there about (1) whether global warming is occuring, (2) if it is occuring is it a natural occurence or is it caused by humans, and (3)what should we as individuals and a society do about these issues. As I mentioned in class, it is very important that you understand what components of the debate are facts and what components of the debate are based on mathematical models or other forms of argument. I think that it is important that you should be able to explain to other people why scientists will never be able to conduct the experiment that will nail down whether or not humans are causing global warming (we have only one earth).

Unfortunately, there is a lot of misinformation about this topic. For example, on Thursday February 5th there was a letter to the Lubbock Avalanche Journal about global warming that clearyly contained some misstatements of fact. I think that it is important for you to have access to good information. Here are some links to what I consider to be some of the best and most reliable sources of information about this topic. Although some of these articles go into much more detail than are required for this class you should know where to find reliable information about this topic.

Further Reading

Carbon cycle- http://www.eoearth.org/article/Carbon_cycle

Global warming- http://www.eoearth.org/article/Global_warming

Global warming Frequenty Asked Questions- http://www.eoearth.org/article/Global_warming_frequently_asked_questions

Climate change FAQ- http://www.eoearth.org/article/Climate_change_FAQs

Intergovenmental Panel on Climate Change- http://www.eoearth.org/article/Intergovernmental_Panel_on_Climate_Change_%28IPCC%29

IPCC Assessment for Policymakers- http://www.eoearth.org/article/IPCC_Fourth_Assessment_Report%2C_Working_Group_I%3A_Summary_for_Policymakers


Expected Learning Outcomes

By the end of this course a fully engaged student should be able to

- diagram the global carbon cycle
- discuss how humans have altered the global carbon cycle
- discuss how the atmospheric concentration of carbon dioxide varies annually
- discuss the proposed relationship between human caused changes in the global carbon cycle and global warming
- discuss alternative causes of global warming
- discuss the experiment that would be required to determine whether or not human activity is the cause of global warming
- articulate and defend their own personal view of how they intend to deal with the global warming issue

Saturday Update

Not surprisingly, my home, Lubbock, TX, is not the center of enviromnetal awareness. In fact, reading articles in our local media denying global warming is a fairly regular occurance. The Saturday(February 7, 2009) issue of the Lubbock Avalance Journal contains another letter to the editor talking about global warming. The letter right refers reader to a site, www.petitionproject.org, where they claim that over 30,000 scientists (9000 of them have Ph. D.s) have signed a petition "firmly disagreeing with global warming theory". I would be interested in what you guys thought about the information available on this site relative to the info on the posts I have listed above.

Ecosystem Ecology- Global Carbon Cycle

Some nutrients cycle at a global level. We will use a simple example of the carbon cycle to illustrate an example of a global cycle (see figure at top of this post).

At the global level the major locations for carbon are living organisms, the atmosphere, water, and rocks. The two most important biological causes of movement between one reservoir and the next are photosynthesis and cellular respiration.

1. Photosyntheis- moves carbon from the atmosphere (for terrestrial organisms) or water (for aquatic organisms) to living organisms. Carbon dioxide ===> glucose

2. Cellular Respiration- moves carbon from living organisms to the atmosphere or water.

glucose ===> carbon dioxide.

Carbon in the Atmosphere

The major source of carbon in the atmosphere is carbon dioxide. Historically, the rate at which carbon dioxide was added to the atmosphere was about equal to the rate at which carbon dioxide was removed from the atmosphere were about equal. Thus, over time the atmospheric contentration of carbon dioxide didn't change very much.

Human Alteration of the Global Carbon Cycle

Humans have altered the global carbon cycle in three main ways.

1) By burning fossil fuels (e.g., gasoline in our cars and coal in our power plants) we have increase the rate at which carbon is moved from rocks to the atmosphere.

2) Deforestation- By cutting down trees for agriculture or development we have reduced the number of plants conducting photosynthesis. Thus, we have decreased the rate at which carbon is moved from the atmosphere to living organisms.

3) By burning trees after deforestation we have increased the rate at which carbon moves from lving organisms to the atmosphere.

Thus, humans have increased the rate at which carbon is being added to the atmosphere while decreasing the rate at which carbon is removed from the atmosphere.

Prediction- the amount of carbon in the atmosphere should be increasing.

Test of this prediction- scientists in Mauna Loa, Hawaii have tested this prediction by measuring the amount of carbon dioxide in the atmosphere over the past 50 years.

MaunLoa Curve- http://www.eoearth.org/article/Mauna_Loa_curve

This curve shows two things. First, that the concentration of carbon dioxide in the atmosphere has indeed increased over time. Second, that there is seasonal variation in the concentration of carbon dioxide in the environment. Carbon dioxide is most abundant in the atmosphere in the North American winter and lowest in the North American winter. This pattern is caused by seasonal variation in the amount of photosynthesis. In the summer, when photosynthetic rates are the highest, carbon dioxide is removed from the atmosphere at a high rate which reduces the amount of carbon in the atmosphere. Because there is more land mass in the Northern Hemispere and most photosynthesis happens on land, the global pattern is determined by seasons in the Northern Hemispere (this is truly a global cycle, carbon dioxide move so quickly though the environment that the conentration is virtually the same all over the world).

Expected Learning Outcomes

At the end of this course a fully engaged student should be able to

- diagram the global carbon cycle and be able to explain how human activity has altered this cycle (TEKS 112.43. 12A).


What is Happening to the Rate Carbon Dioxide is Being Added to the Atmosphere?

Here is an article from the Associated Press entitled- Climate Warming Gasses Rising Faster than Expected that was published yesterday. Chris Field, one of the scientists quoted in this article, was one of my professors at University of Utah.

CHICAGO (AP) -- Despite widespread concern over global warming, humans are adding carbon to the atmosphere even faster than in the 1990s, researchers warned Saturday. Carbon dioxide and other gases added to the air by industrial and other activities have been blamed for rising temperatures, increasing worries about possible major changes in weather and climate.

Carbon emissions have been growing at 3.5 percent per year since 2000, up sharply from the 0.9 percent per year in the 1990s, Christopher Field of the Carnegie Institution for Science told the annual meeting of the American Association for the Advancement of Science.

''It is now outside the entire envelope of possibilities'' considered in the 2007 report of the International Panel on Climate Change, he said. The IPCC and former vice president Al Gore received the Nobel Prize for drawing attention to the dangers of climate change.

The largest factor in this increase is the widespread adoption of coal as an energy source, Field said, ''and without aggressive attention societies will continue to focus on the energy sources that are cheapest, and that means coal.''

Past projections for declines in the emissions of greenhouse gases were too optimistic, he added. No part of the world had a decline in emissions from 2000 to 2008.

Anny Cazenave of France's National Center for Space Studies told the meeting that improved satellite measurements show that sea levels are rising faster than had been expected. Rising oceans can pose a threat to low level areas such as South Florida, New York and other coastal areas as the ocean warms and expands and as water is added from melting ice sheets.

And the rise is uneven, with the fastest rising areas at about 1 centimeter -- 0.39 inch -- per year in parts of the North Atlantic, western Pacific and the Southern Ocean surrounding Antarctica, she said.

Also, highly promoted efforts to curb carbon emissions through the use of biofuels may even backfire, other researchers said. Demand for biologically based fuels has led to the growing of more corn in the United States, but that means fields were switched from soybeans to corn, explained Michael Coe of the Woods Hole Research Center. But there was no decline in the demand for soy, he said, meaning other countries, such as Brazil, increased their soy crops to make up for the deficit.
In turn, Brazil created more soy fields by destroying tropical forests, which tend to soak up carbon dioxide. Instead the forests were burned, releasing the gasses into the air. The increased emissions from Brazil swamp any declines recorded by the United States, he said.

Holly Gibbs of Stanford University said that if crops like sugar and oil palm are planted after tropical forests are burned, the extra carbon released may be balanced by lower emissions from biofuel in 40 to 120 years, but for crops such as corn and cassava it can take hundreds of years to break equal.

''If we run our cars on biofuels produced in the tropics, chances will be good that we are effectively burning rainforests in our gas tanks,'' she said.

However, there could be benefits from planting crops for biofuels on degraded land, such as fields that are not offering low productivity due to salinity, soil erosion or nutrient leaching.

''In a sense that would be restoring land to a higher potential,'' she said. But there would be costs in fertilizer and improved farming practices.

In some cases simply allowing the degraded land to return to forest might be the best answer, she said.

Ecosystem Ecology- Nitrogen Cycles Within an Ecosystem

Ecosystem ecologists define nutrients as biologically important elements (e.g., C, N. P, S). Nutrients can cycle either within ecosystems or globally

Nitrogen Cycle

We will consider a very simple example of the nitrogen cycle to illustrate how nutrients cycle within an ecosystem (ie., nutrient cycle within a prairie in Kansas or within a rainforest in Brazil).

Plants pick up nitrogen from the soil, herbivores get their nitrogen from eating plants, and carnivores get their nitrogen by eating herbivores. When organisms die there is nitrogen held in their dead bodies. Decomposers get their nitrogen from dead bodies and return nitrogen to the soil where it can be picked up by plants. Thus, it is possible for the same atom of nitrogen to recylce through the ecosystem over and over.

Ecosystem ecologists are interested in understanding how much nitrogen is found in plants, animals, soil, etc. and the rate at which nitrogen moves from one place to another.

What factors can influence the movement of nitrogen through and ecosystem and why is this important? Decomposers are responsible for moving nitrogen from dead bodies of organisms to the soil. The major decomposers, fungi and bacteria, thrive in warm and wet environments. Thus, we might expect the rates of decomposition in tropical rainforests to be much faster than in the desert. Thus, nutrients in dead bodies are quickly returned to the soil in tropical rainforests where they are quickly picked up by plants. Alternatively, the slow rate of decomposition can tie up nitrogen in dead bodies of plants so that nitrogen is not available for plant growth.

Expected Learning Outcomes

At the end of this course a fully engaged student should be able to

- diagram the nitrogen cycle within an ecosystem and explain how the rate of movement from one reservoir to the next can vary between environments (TEKS 112.43. 12A & 12E).

-develop curricular material to illustrate nitrogen cycling withing a chosen environment (TEKS 112.43. 12A & 12E).

Ecosytem Ecology- Energy Flow

Ecosystems include all of the biotic components that we talked about in a community as well as abiotic characteristics. Ecosystem ecologists focus on the flow of energy and nutrients through the ecosystem.

Energy Flow

Energy is required to do the "biological work" needed to keep species alive. Almost all of the energy used by biological organisms on earth originates as electromagnetic energy from the sun that is then converted into chemical energy by the process of photosynthesis. Energy then flows up the food chain from one tropic level to the next.

Secondary Consumers
^
Primary Consumers
^
Primary Producers

Photosynthetic organism (plants and photosynthetic bacteria) are known as "Primary Producers" and they make up the bottom of most food chains. Species that get their energy by eating primary producers are known as "Primary Consumers". Organims that get their energy by eating primary consumers are known as "Secondary Consumers".
Thus, energy moves up the food chain from primary producers to primary consumers to secondary consumers.

All organisms are releasing energy to the atmosphere in the form of heat (you are releasing heat right now by the effort you are making to keep your eyes open).

When organims die energy is held in their dead bodies. Decomposers "feed" on the energy held in dead bodies and decomposers also release energy to the atmosphere as heat.

3 Key Facts About Energy Flow

1. Energy enters the system as sunlight energy, moves up the food chain, and is ultimately lost as heat.

2. The flow of energy is one way only.

3. The flow of energy from one trophic level to the next is inefficient. Only approximately 10% of the energy held in one trophic level is passed on to the level above it. The

Energy Pyramid

Because the flow of enrgy up the food chain is inefficient, the amount of energy available in each trophic level decreases as you move up the food chain. This can be shown in a diagram known as an "energy pyramid" (see example at the top of the post).

This is important for two reasons. First, there is a limit to how long food chains can be because there is eventually not enough energy available to add another level to the chain. Second, the amount of energy in a trophic level influences the population size of species in the trophic level above it. For example, all else being equal we expect population sizes of predators to be smaller than the population sizes of herbivores because they have less energy to feed on.

Expected Learning Outcomes

At the end of this course a fully engaged student should be able to

- identity the source of most energy used by biological organisms on earth and explain the energy transformations experienced by this energy (TEKS 112.43. 9D,12A, & 12E and TEKS 112.44. 6A, 6B, & 6D)

- diagram the energy pyramid and explain why it has the shape it does and how it affects population structure at different trophic levels (TEKS 112.43. 9D & 12A and TEKS 112.44. 6B, 6C, & 6D).

- diagram food chains and food webs from a variety of environments (TEKS 112.43. 9D, 12A, & 12E and TEKS 112.44. 6B, 6C, & 6D).

- develop curricular materials to illustrate the food web and pattern of energy flow in a chosen environment (TEKS 112.43. 9D, 12A, & 12E and TEKS 112.44. 6B, 6C, & 6D).

Community Ecology- Food Webs

The take home point of my classes on Community Ecology is the "the world is complicated!" It is relatively simple to think about species interactions when we are studying interactions between only two species at at a time. However, species exist in very complex food webs. All species are potentially a source of food for other species and all species (except for plants) must use another species as food. (of course, plants are competing with each other for light, nutrients, and water!).

Direct Effects

Species can directly influence the growth rate or population size of another species directly by (1) acting as a source of food, (2) by using the other species as a source of food, or (3) by interference competition.

Let's try an example. Imagine that we are interested in studying the ecology of the Serengetti National Park in Tanzania. To keep things simple lets say that (1) lions eat wildebeasts, and (2) leopards eat wildebeasts. If we increase the population size of lions, then we would expect the population size of their prey (say wildebeasts) to decrease because there are more lions preying on wildebeasts. Alternatively, if we increase the population size of wildebeasts then we would expect the population size of lions to increase because there is less food for lions. These would both be examples of "direct effects"

Indirect Effects

What happens to the population size of leopards if we increase the population size of lions? If we assume that there is not interference competition going on between lions and leopards then we see that there are no direct effects of lions on leopards. However, it is easy to see that changing the population size of lions will affect the population size of leopards. If we increase the population size of lions that would decrease the population size of wildebeasts and decreasing the population size of wildebeasts would decrease the population size of leopards. Thus, lions have an indirect effect on leopards through their effects on the population size of wildebeasts. Lions and leopards are expoloitative competitors which tells us that exploitative competition is an indirect interaction.

The World is Complicated

Thus, all species are being influenced by a variety of direct and indirect effects. Thus, altering the population size of a single species may have effects on many other species and the population size of a single species can be influenced by many other species.

Actually determing how changing the population size of a specific species will affect the rest of the community is difficult to determine without careful long-term manipulative experiments in the field. These studies are costly and have therefore only been conducted in a few ecosystems.

Keystone Species

One of the interesting outcomes of studies of complex interactions is the discovery of "keystone species". Emmet Duffy's article on the EoE discusses some of the classic examples of keystone species

Expected Learning Outcomes (slightly modified from the Ecology Reader)

At the end of this course a fully engaged student should be able to

- determine the position of a species in the food chain (TEKS 112.43 10D, 12B, 12E and TEKS 112.44 6B)

- distinguish between direct and indirect effects and provide examples of indirect ecological effects occurring in specific communities (TEKS 112.43 12B)

- identify examples of keystone species (TEKS 112.43 12B and TEKS 112.44 4D, 4E)

Community Ecology- Species Interactions

Community Ecology is one of fhe most interesting topics in all of ecology (in my opinion). The major biological interactions between species (competition, predation, and mutualism)are important because they can influence aspects of community structure such as species diversity, aspects of population biology including population size, and act as important selective pressures influencing the behavior and morphology of species.

Competition

Expected Learning Outcomes

At the end of this course a fully engaged student should be able to

- identify and explain examples of exploitative and interference competition from a variety of environments (TEKS 112.43. 12 B & 12 E and TEKS 112.44. 4 A).

- define the competitive exclusion principle and explain how this principle can influence patterns of community structure (TEKS 112.43. 12 B & 12 E).

- develop curricular materials to illustrate competition in a particular environment (TEKS 112.43. 12 B & 12 E and TEKS 112.44. 4 A).

Predation

Expected Learning Outcomes

At the end of this course a fully engaged student should be able to

- identify and explain examples of predation, herbivory, and parasitism from a variety of environments (TEKS 112.43. 12 B & 12 E and TEKS 112.44. 4A).

- identify examples of morphological and behavioral adaptations that animals have to help capture their food (TEKS 112.43 7B, 12B)

- identify examples of morphological, biochemical, or behavioral adaptations that animals have to protect them from predators (TEKS 112.43 7B, 12B)

- explain the role that predation plays in regulating population sizes of species (TEKS 112.43. 12 B & 12 E and TEKS 112.44 7A).

- explain how predation can influence the species richness of a community (TEKS 112.43. 12B)

- develop curricular material to illustrate predation in a chosen environment (TEKS 112.43. 12 B & 12 E and TEKS 112.44. 4A).

Mutualisms

Expected Learning Outcomes

At the end of this course a fully engaged student should be able to

- identify and explain examples of mutualisms from a variety of habitats (TEKS 112.43. 12 B and 12 E).

- explain the role that mutualisms can play in determining community structure (TEKS 112.43. 12 B and 12 E).

- develop curricular materials to illustrate mutualism in a chosen environment (TEKS 112.43. 12 B and 12 E).

Human Population Growth

I have spent a lot of time telling you that exponential growth is an unrealistic model of population growth. Interestingly, human populations have experienced exponential-like growth. How can this be?

What makes humans different from other species?

In other species per capita birth rates and per capita deaths rates are density dependent. However, as human populations have increased there has been no corresponding decline in per rates or increase in death rates. What makes humans different from other species?

Humans have the ability to alter their environment so that they can avoid the density dependent effects on birth and death rates. 1) Humans have increased food production by improvements in agriculture (e.g., irrigation, fertilization, mechanized farming, genetically improved crops). 2) Humans have been able to decrease death rates by improvements in medicine and public health (things as simple as not pooping in the water you drink helps a lot!). 3) Humans have elimnated most human predators (ocassionally, someone gets killed by a shark or a mountain lion).

Where is human population growth occuring?

The rates of human population growth are not the same in all regions. Today, human populations are increasing in size much faster in developing countries (e.g., Mexico, other countries in Central America, Africa, and Southeast Asia) than they are in developed countries (e.g, USA, Canda, Western Europe). The figure at the top of this post shows the patterns of population growth in developed and developing nations.

Thus we see that populations are increasing most rapidly in the countries that are least able to deal with a rapidly increasing population. See "Population Challenges-The Basics" that can be downloaded from the Population Institute's website.
http://www.populationinstitute.org/population-issues/index.php

Human Population Growth Proble?

There is a great deal of debate about whether increasing human populations are a problem or not, and if they are what should be done about it. Unfortunately, we don't have time to discuss this issue in very much detail in class. My personal opinion is that we have too many people consuming too many resources and the last thing that we need are billions more people living on the planet. This is an issue that I am always intersted in talking more about if you would like to chat.

Further Reading

See the article "Human Population Explostion" from the EoE.
http://www.eoearth.org/article/Human_population_explosion

Pay particular attention to the "demographic transition".

Really Cool Video

Here is a link to a YouTube video on "World Population" The first minute and a half or so is a little boring, so you can skip over it if you wish. However, I think the animation showing when and where human population growth has been occuring is really cool.

http://www.youtube.com/watch?v=4BbkQiQyaYc

Expected Learning Outcomes

By the end of this course a fully engaged student should be able to

- describe patterns of human population growth in developed and developing nations
- discuss some reasons why the pattern of population growth in humans is so different from that in other species
- describe the demographic transition
- discuss their own personal view of human population growth.