General Ecology: Lecture 22
November 30, 2005
I.
Biogeochemistry: Focus on carbon cycling (Ch. 25, pp. 514-516; Ch. 26, pp. 527-529;
see also Ch. 32—will skim key points)
A.
Overview: Like all important materials required by organisms, carbon cycles
between living and non-living components of the earth (including its atmosphere,
biosphere and geosphere). [Fig. 25.13]
B.
What processes control the amount of atmospheric CO2?
1.
Major sinks for CO2: these processes reduce the amount of CO2 in the
atmosphere
a.
Primary producers:

Both marine and terrestrial primary producers act as sink.

Which ecosystems are most important for reducing
atmospheric carbon dioxide in this way?

HINT: See Table 24.1
b.
Ocean water (deep) and ocean sediments (mineral). Only "semipermanent" carbon dioxide sink.

NOTE: Due to both the primary producers and non-living
sinks for carbon dioxide, the ocean is by far the major sink for
carbon dioxide!
c.
The dead organic matter within soils is also a major sink, especially
the lower soil layers

Dead organic matter in both the terrestrial and marine
environment both slowly form fossil fuels at a very low rate.
2.
Major sources of atmospheric CO2 since organisms appeared: These
processes have put carbon dioxide into the atmosphere through much of
earth’s history.
a.
Plant and animal respiration (terrestrial and marine)
b.
Decomposition of organic remains. Organic carbon is converted
into CO2.
c.
Naturally occurring fires
3.
Anthropogenic increase in sources/reduction of sinks, especially
accelerated during past 50 years.
a.
Burning of fossil fuels

What are fossil fuels and how were they produced?

Oil and natural gas (Formed from what? How? Know!)

Coal (Formed from what? How? Know!)

What was the original energy source for these fossil fuels?

According to John H. Gibbons et al. (Scientific American,
1989): "Humankind expends in one year the amount of fossil
fuel that it took nature roughly a million years to produce."

Look at the imbalance here!!!
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b.
C.
Burning of rain forest for agricultural land

Again, we are releasing, all at once, carbon that has been
"locked up" in the biosphere as organic carbon.

This is a double-whammy on the environment, because it
releases CO2 and decreases its usefulness as a sink.
c.
Other losses of plant cover due to development
d.
Loss of coral reefs

Reefs are made of calcium carbonate deposited by the coral
animal. Without reefs, less CO2 is incorporated into reefs and
instead it remains in the atmosphere.
4.
In sum, we are increasing CO2 sources and reducing CO2 sinks. So, the
net result is more CO2 in the atmosphere!!! This is real!
Why does the increase of CO2 matter? Is global warming real?
1.
Greenhouse effect, review.
2.
Current data on global temperature increases
a.
There is already a documented 0.5 ºC increase in the earth’s average
temperature over the past 100 years.
b.
Measurements on Antarctic Peninsula show more extreme patterns:
Summer temperatures in this region have increased by 5°C!
3.
Uncertainties
a.
How high will the temperature go?
b.
How much excess carbon will the deep ocean water and sediments be
able to absorb?

Temperature increase reduces the ability of ocean water to hold
carbon dioxide. So, there could be a positive, runaway
feedback loop involving temperature and carbon dioxide.
4.
Potential consequences of global warming
a.
Coastal flooding would be definite
b.
Climates of specific regions would change.

Increases in El Nino like conditions, so massive drought in
some areas, increased rainfall in others.

Certainly would alter the world as we know it.
c.
Increased rates of extinction

But some organisms will shift their ranges. Others may not
have the mobility or time to respond in this way.

Evidence of species that have already shifted their
distribution

Malaria-infected mosquitoes

Adelie penguins
5.
Is there anything we can still do to insure that the worst-case scenarios?

Reduce sources and increase sinks. But how?
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Study questions
1.
What processes control the amount of carbon dioxide in the atmosphere? Summarize in
terms of:
a.
Major sinks for carbon dioxide both terrestrial and marine (be specific—for
example don’t just say “the ocean” but describe where and how it is stored)
b.
Major sources of atmospheric carbon dioxide, distinguishing between

Those that have been sources since around the time organisms appeared on
earth.

Anthropogenic sources that have accelerated especially in the past 50 years.
2.
What are fossil fuels? Be able to name the major fossil fuels and the material from which
they originated.
3.
From what source, originally, did the energy now contained in fossil fuels arise?
4.
Since fossil fuels are “natural” and thus the carbon dioxide within them originally from
the atmosphere in the first place, why is it a problem to be using them now?
5.
Is there actual evidence that global warming has already occurred? If so, describe that
evidence.
6.
What are the major scientific uncertainties related to global warming?
7.
What effects could temperature increase have on the carbon dioxide stores already
sequestered in the ocean? In term, what effect could this then have on global temperature?
8.
What are some of the potential ecological consequences of global warming?
9.
Why might some species shift their ranges, while others may not be able to do so?
10.
What can we do now to minimize the warming that will occur and thus minimize the most
extreme consequences?
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