Rainforest and Oxygen Production
Lidia LoPinto
question. Does the rainforest produce more oxygen than
it consumes?
Most plants produce more oxygen than they consume. But this
is balanced out by the fact that there are animals in the
forest and decay taking place at the forest flow. If the
forest was not in balance, pretty soon, the oxygen level
would go beyond the 21?% and there might be combustion or
a forest fire.
As an aside, I distinctly recall learning in biology in
8th or 9th grade that most of the oxygen we consume is
generated on the surface of the ocean by algea. Much of
it is trapped in the ocean as well. The idea that if
we were to cut down all of the forest we would suffocate for
lack of oxygen is wrong. The problem with cutting down
forests is the change in climate, from wet to dry. The amazon
forest probably being the last of the forests we will destroy.
We have destroyed many other forests throughout the US. It
was said that a squirril in North America could travel through
the trees never touching ground from east to west. However,
I wonder what reaction by Americans would have been if
another country, say England, prevented them from cutting down
trees to make room for farmlands in order to protect the world
ecology? Yet, we pretend to stop Brazil from doing exactly
what we did. Is that fair? What are your comments? Do
we have the right to stop them from cutting their own forests?
Didn't we do that in our own land? How much forest is enough?
Are the forests we have set aside as wilderness and for paper
production enough? And, the final question, should we all give
up our own lives, cut down our own pupulation in order to
make more room for trees and squirrels?
Food for debate.
Hope it gets interesting
--
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| e-mail Lid...@ix.netcom.com |
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John McCarthy
that an excess oxygen is produced but that a shortage of CO2 occurs.
Oxygen makes up 21 percent of the atmosphere and CO2 0.03 percent.
Plants have evolved to do their best on this tiny amount of CO2, but
most of them do better in an enriched atmosphere as many recent
experiments have shown.
This doesn't guarantee that more CO2 in the atmosphere would be good
for us. Maybe it would get pleasantly warm and maybe unpleasantly
hot, and surely different places would be affected differently. These
points have been made many times on this newsgroup by different
people.
--
John McCarthy, Computer Science Department, Stanford, CA 94305
*
He who refuses to do arithmetic is doomed to talk nonsense.
http://www-formal.stanford.edu/jmc/progress/
Len Evens
Lidia LoPinto <lid...@ix.netcom.com> wrote:
>Someone on this newsgroup finally asked a very intelligent
>question. Does the rainforest produce more oxygen than
>it consumes?
>
I feel uncomfortable talking about Oxygen since I have no direct
knowledge of the subject, but I have spent some time trying to
understand the Carbon cycle, which I presume mirrors what happens
to Oxygen pretty well. So here are my opinions for what they
are worth. (My reference for most of this is Climate Change, 1994
by the Intergovernmental Panel on Climate Change, published by
Cambridge Unviersity Press.)
First, it is well known that the Oxygen content of the atmosphere
has varied rather significantly over geological time. (My
refrence for that is in my office, so I'm afraid I can't come up with
it right now, but if anyone interested sends me e-mail, I
will try to respond.) However, anything that is happening now
is only going to have a minor effect on the level of Oxygen in
the atmosphere on the time scale of human activities.
If we look at the Carbon cycle instead, we find that human activity
is removing considerable parts of the tropical rain forests
(roughly estimated to be about 1.6 GtC/ye during the 80s) but that
has been approximately compensated for by additional growth of
vegetation, mainly in Northern hemisphere temperate forests.
>Most plants produce more oxygen than they consume. But this
>is balanced out by the fact that there are animals in the
>forest and decay taking place at the forest flow. If the
>forest was not in balance, pretty soon, the oxygen level
>would go beyond the 21?% and there might be combustion or
>a forest fire.
>
>As an aside, I distinctly recall learning in biology in
>8th or 9th grade that most of the oxygen we consume is
>generated on the surface of the ocean by algea.
I have seen this said too and I wish someone would explain it.
Again if the Carbon cycle mirrors the Oxygen cycle, the magnitudes
of the exchanges between ocean and atmosphere and between land
vegetation and atmosphere are both roughly in balance. It is
true that the oceans are sopping up slightly more CO_2 than they
are returning to the atmosphere. If Oxygen mirrors this the
oceans might be contributing some slight increment to the
atmosphere. Of course, the largest change comes about from
human activities. But as I mentioned above, none of this
is going to have a significant effect on Oxygen concentration
in the short run. I believe that on a geological time scale
it may be true that oceanic biota are responsible for the great
bulk of the Oxygen in the atmosphere.
Ray Pierrehumbert explained some of this in a posting several
months ago, and perhaps he or someone else will clarify the
matter again.
>Much of
>it is trapped in the ocean as well. The idea that if
>we were to cut down all of the forest we would suffocate for
>lack of oxygen is wrong. The problem with cutting down
>forests is the change in climate, from wet to dry. The amazon
>forest probably being the last of the forests we will destroy.
I think the major problem with destroying old growth forests of
all kinds is the loss of biodiversity. Edward Wilson and
others have pointed out that we may be going through what on
a geological time scale will look like one of the major extinctions.
There is some controversy about their conclusions, but apparently
most biologists take this very seriously.
>We have destroyed many other forests throughout the US. It
>was said that a squirril in North America could travel through
>the trees never touching ground from east to west. However,
>I wonder what reaction by Americans would have been if
>another country, say England, prevented them from cutting down
>trees to make room for farmlands in order to protect the world
>ecology? Yet, we pretend to stop Brazil from doing exactly
>what we did. Is that fair? What are your comments? Do
>we have the right to stop them from cutting their own forests?
>Didn't we do that in our own land? How much forest is enough?
>Are the forests we have set aside as wilderness and for paper
>production enough? And, the final question, should we all give
>up our own lives, cut down our own pupulation in order to
>make more room for trees and squirrels?
>
Unfortunately, it is not simply a matter of the rights of
wildlife vs. the rights of human beings. Ecologists claim
that the `natural' or original ecology performs essential functions
which all life, including ours, depends on. Many of these
functions are unknown. Making our planet into a human controlled
park may sound attractive, but we don't know what we will lose
if we attempt it. It could be that we will end up destroying
our own species in the process.
>Food for debate.
>Hope it gets interesting
It already has.
Leonard Evens l...@math.nwu.edu 708-491-5537
Dept. of Mathematics, Northwestern Univ., Evanston, IL 60208
Len Evens
John McCarthy <j...@cs.Stanford.EDU> wrote:
>What happens when forests sequester all the carbon they can get is not
>that an excess oxygen is produced but that a shortage of CO2 occurs.
>Oxygen makes up 21 percent of the atmosphere and CO2 0.03 percent.
>Plants have evolved to do their best on this tiny amount of CO2, but
>most of them do better in an enriched atmosphere as many recent
>experiments have shown.
>
This is still controversial. Some plants, particularly many
important in agriculture appear to do better, at least under
controlled conditions. But whether or not this will persist
in real life is unclear. Also, this ignores changes in climate which
may occur if increased CO_2 concentration leads to such change,
as you mention below.
Other plants may not do so well. Also, a lot of this depends
on other available nutrients. This is not something we can
consider settled. There are at least as many uncertainties
as there are in predictions of global warming, if not more.
>This doesn't guarantee that more CO2 in the atmosphere would be good
>for us. Maybe it would get pleasantly warm and maybe unpleasantly
>hot, and surely different places would be affected differently. These
>points have been made many times on this newsgroup by different
>people.
>--
>John McCarthy, Computer Science Department, Stanford, CA 94305
>*
>He who refuses to do arithmetic is doomed to talk nonsense.
>http://www-formal.stanford.edu/jmc/progress/
>
>
You don't mention it, but let me also comment on plant growth
as a negative feedback on increase of CO_2 concentration.
There is such a negative feedback called CO_2 fertilization
and a related feedback called Nitrogen fertilization, but although
these somewhat limit the growth in atmospheric CO_2, they do not
come close to cancelling it out. Hence, if present trends in
the use of fossil fuels and other human activities continue
with population growth excacerbating them, we can't expect
plants to come to our rescue and cancel out the increased
CO_2. However, planting as many trees and other vegetation
as possible, may help a bit, if the latest research is correct.
How does any of this apply to lawns and the other usual
types of landscaping of private property in the US? I've
always disliked lawns and liked trees, but I don't know what
difference it makes.
R T Tyrrell
: First, it is well known that the Oxygen content of the atmosphere
: has varied rather significantly over geological time. (My
: refrence for that is in my office, so I'm afraid I can't come up with
: it right now, but if anyone interested sends me e-mail, I
: will try to respond.) However, anything that is happening now
: is only going to have a minor effect on the level of Oxygen in
: the atmosphere on the time scale of human activities.
Yes. There is such a vast reservoir of oxygen in the atmosphere (21% of
it) that even if we were to fell all of the forests and poison all of the
oceans (a horrible thought), it would still take millions of years before
the amount of oxygen in the atmosphere declined enough to make breathing
difficult. There is just *such a lot* of it already in the atmosphere.
As other posters have noted, the situation is different for CO2 because
there is very much less CO2 in the atmosphere (approx 0.035% of it),
and so a flux of the same absolute size has a much greater fractional
(percentage) effect. It's like giving $10 either to a tramp or to Bill
Gates. You give the same amount but the relative effects are much
greater in one case than th other.
: >As an aside, I distinctly recall learning in biology in
: >8th or 9th grade that most of the oxygen we consume is
: >generated on the surface of the ocean by algea.
: I have seen this said too and I wish someone would explain it.
: Again if the Carbon cycle mirrors the Oxygen cycle, the magnitudes
: of the exchanges between ocean and atmosphere and between land
: vegetation and atmosphere are both roughly in balance. It is
: true that the oceans are sopping up slightly more CO_2 than they
: are returning to the atmosphere. If Oxygen mirrors this the
: oceans might be contributing some slight increment to the
: atmosphere. Of course, the largest change comes about from
: human activities. But as I mentioned above, none of this
: is going to have a significant effect on Oxygen concentration
: in the short run. I believe that on a geological time scale
: it may be true that oceanic biota are responsible for the great
: bulk of the Oxygen in the atmosphere.
: Ray Pierrehumbert explained some of this in a posting several
: months ago, and perhaps he or someone else will clarify the
: matter again.
It's all to do with the flow of organic matter into long-term
reservoirs, i.e. rocks. When organic matter is produced by
photosynthesis (CO2 + H2O --> CH2O + O2) then this causes a
decrease in CO2 and an increase in O2, but when the carbohydrates
(CH2O) are broken down again (by respiration or decay) then the reverse
reaction takes place and there is no net effect on CO2 or O2.
Only when the organic matter is formed and is then stored away
before being regenerated, is there a sustained change to the
reservoirs of CO2 and O2.
Most of the biological production on the land is regenerated and
very little gets incorporated into sediments. I'm not quite clear
why this is (scouring effects of ice sheets? high levels of biological
decomposers in soils?), but it means that the abundant growth on land
has very little long-term effect on CO2 and O2 because it all gets
regenerated before it can become incorporated into rocks. Life
in the sea, on the other hand, leads to some dead organic matter
sinking right down to the ocean floor, where conditions are much more
conducive to the formation of sedimentary rocks. Therefore marine
life has a greater potential to affect CO2 and O2 in the atmosphere,
in the long term.
It's also worth remembering that oxygen concentrations were very
high before life ever appeared on land (500 million years or so
ago), and this confirms that terrestrial life is not required
in order to get high O2 in the atmosphere.
Toby Tyrrell
Plymouth Marine Laboratory,
Prospect Place,
Plymouth PL1 3DU.