Naked Science Forum
Life Sciences => Plant Sciences, Zoology & Evolution => Topic started by: 4getmenot on 03/08/2006 05:17:54
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How r we going to breathe if they keep cutting down our oxygen sources??? How many trees have to exist to maintain our lives???
k
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Simple answer is zero.
The first oxygen created on this planet was by algae.
What you are correct in suggesting is that we need photosynthesis in order to have oxygen, but what you are incorrect in assuming is that trees are the only source of photosynthesis.
It is also the case that a stable mature forest (i.e. one that is not actively growing in size) cannot be a net producer of oxygen. Newly formed or growing forests will be a net producer of oxygen, as the carbon it requires for growth is extracted from the atmosphere to create its new growth, and the oxygen excreted as a waste product.
The reality is that the green moss you may clear from your driveway or other places where you may find it unsightly is just as busy creating oxygen as any tree, as is the grass all around you, and much else.
We have a particular emotional attachment to trees, just as we have a repulsion to green algae, and have a repulsion to untidy moss invading out clean property, but all of them are oxygen producers.
George
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It is the CO2 you have to watch.
Oxygen forms about 20.9% of the atmosphere. CO2 forms .038%
If you stopped all photosynthesis then the proportions would change. If oxygen was reduced to 18% this may be noticable but bareable like breathing when up a mountain. However if the CO2 is raised to around 2% it is reaching toxic levels. Therefore it is the CO2 level you need to watch not the oxygen level.
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I would be more concerned at the climate change impacts than on whether we would still be able to breathe.
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quote:
Originally posted by crandles
It is the CO2 you have to watch.
Oxygen forms about 20.9% of the atmosphere. CO2 forms .038%
If you stopped all photosynthesis then the proportions would change. If oxygen was reduced to 18% this may be noticable but bareable like breathing when up a mountain. However if the CO2 is raised to around 2% it is reaching toxic levels. Therefore it is the CO2 level you need to watch not the oxygen level.
This may indeed be the case, but it would amount to a 50 fold increase over what exists at present.
It should also be noted that as O2 reduces, other sources of natural combustion (such as forest fires) will reduce. As CO2 increases, so other animal life will also begin to die off, so reducing natural CO2 production.
I am not saying that a 50 fold increase in CO2 is desirable, only that there are lots of natural negative feedback loops which will make that difficult (although not impossible) to achieve.
George
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I can imagine a future when mostly all the trees are gone and everyone lives in massive sky scrapers covered from top to bottom in photosynthetic moss or something lol. Maybe I will right a sci-fi novel.
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Originally posted by Mjhavok
I can imagine a future when mostly all the trees are gone and everyone lives in massive sky scrapes covered from top to bottom in photosynthetic moss or something lol. Maybe I will right a sci-fi novel.
I can imagine this - although whether the moss is fully artificial, or merely GM moss, may be open to question.
George
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or we will all end up living in bubbles....moss huh? i did not know that, but just the same...the land and were it grows is little by littel being destoryed leaving us with little time to figure out how we will live with our own demise..
k
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quote:
Originally posted by 4getmenot
or we will all end up living in bubbles....moss huh? i did not know that, but just the same...the land and were it grows is little by littel being destoryed leaving us with little time to figure out how we will live with our own demise..
Firstly, two thirds of the surface of the Earth is covered by ocean, not exposed land. The oceans also provide photosynthesis, although we do not yet properly understand how the mechanics of this, or how significant it might be.
Secondly, what do you mean by 'destroyed'? There is still a lot of green out there, although in some areas the tendency is to move from slow growing trees to fast growing grasses. It is true that some areas are being overfarmed, and the nutrients being exhauseted from the soil, but in other areas there is new farmland being created.
We are certainly changing the surface of the Earth, but then the Earth has never remained static - but what does it mean to use the word 'destroy' in this context?
George
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if we continue to take or "destroy" forrests and jungles ect...and i understand we use what we take, but still we are using more than we are replacing..then you are saying that we will still survive because grass will provide our oxygen?? does the ocean provide oxygen? There is still green out there, but little by little it is less and less with more and more people populating this earth we might just run out of room also for houses and condos and parking lots..ect.. no more room for "greenery" or oxygen producing areas to grow. You can cut down a section of the forest and plant the same amount, but it will not be the same and takes time to grow back..prabaly by the time it takes to grow the tree back they wil need the space for people or something...ya know? do you understand what i mean as far as what we take verses what we replace? I might not be writing it correctly to get my point across, i know what i am trying to say, but i do not think it coming out right...lol
k
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quote:
Originally posted by 4getmenot
or we will all end up living in bubbles....moss huh? i did not know that, but just the same...the land and were it grows is little by littel being destoryed leaving us with little time to figure out how we will live with our own demise..
k
Do you mine whole populations inside geodesic domes.
Steven
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In a time of universal deceit - telling the truth is a revolutionary act.
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quote:
Originally posted by 4getmenot
if we continue to take or "destroy" forrests and jungles ect...and i understand we use what we take, but still we are using more than we are replacing..then you are saying that we will still survive because grass will provide our oxygen?? does the ocean provide oxygen?
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There is algae in the ocean, and don't forget that life probably started in the oceans.
There is still green out there, but little by little it is less and less with more and more people populating this earth we might just run out of room also for houses and condos and parking lots..ect.. no more room for "greenery" or oxygen producing areas to grow.
But at the same time, with retreating ice, we may actually have more room for greenery to grow.
It is very unlikely there will much change in the amount of oxygen in the atmosphere, since any major reduction in the oxygen would also cause a reduction in oxygen consuming processes. In the extreme, ofcourse one could contemplate a situation where all oxygen producing processes cease, but long before then all oxygen consuming processes would have ceased.
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You can cut down a section of the forest and plant the same amount, but it will not be the same and takes time to grow back..prabaly by the time it takes to grow the tree back they wil need the space for people or something.
But it is only growing trees that generate oxygen – when a tree no longer grows, it then no longer consume carbon dioxide, and will no longer produce oxygen.
The advantage with grasses over trees is that they actually grow faster than trees, and so must consume more CO2, and thus produce more oxygen.
Ofcourse, the counter argument is that when the grass dies, and either decomposes or is burnt, then it will likely consume the oxygen that it previously produced (the same could also be said when a tree dies).
George
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There is still green out there, but little by little it is less and less with more and more people populating this earth we might just run out of room also for houses and condos and parking lots..ect.. no more room for "greenery" or oxygen producing areas to grow.
The little by little argument is true but not relevant. It is true it is running out but unless you question the rate at which it is running out and therefore are able to see whether the issue becomes a serious problem within a meaningful timescale it is meaningless.
In this case we don't have to calculate the rate at which the space for necessary greenery to produce oxygen is running out because we can see it is never going to be a problem. Before space for greenery to produce oxygen runs out, carbon dioxide would reach toxic level. I think other constraints will become problems before carbon dioxide becomes toxic. Lack of food requiring extra farmland could put pressure on forrest areas but a significant reduction of forrest areas in too short a space of time could cause rapid climate change. Other scenarios where climate change is solved but other problems cause limits are possible.
The Earth's volumetric radius is 6371km giving a surface area of 5E+14 square metres. If 10 square metres (whether ocean or land) is sufficient to grow enough food for 1 person and this was the only limit on population then population could reach 5E+13 which is around 2000 times the current population.
However, such calculations may well all be an irrelevance as birth rates seem to decline the more women are educated and given other life choices. So population might easily stabilise before we get near such limits.
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Originally posted by crandles
However, such calculations may well all be an irrelevance as birth rates seem to decline the more women are educated and given other life choices. So population might easily stabilise before we get near such limits.
Maybe off topic, but are we talking about stabilisation, or are we talking about a reversal and the start of a decline in population (the caveat being that we are talking about human population, not the population of machines within human society).
George
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I was only really talking about population not continuing to rise which could be either stabilisation or a decline. I expect declines to occur with things like a flu pandemic. If the worldwide birth rate was less than 2 per female after such a pandemic then I would expect the birth rate to rise so that you would get an oscillating stabilisation rather than a perfectly flat stabilisation. There is a lot of speculation in that rather than it being scientific. The more scientific point I was trying to repeat was that oxygen isn't a limiting factor.
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I did't know that trees stopped producing oxygen after a certain point.
k
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Originally posted by 4getmenot
I did't know that trees stopped producing oxygen after a certain point.
It is not as simple as to say that trees stop producing oxygen at a certain point. So long as a tree is alive, there will always be new growth on the tree, and that new growth will require new oxygen to be produced. The point is that when you look at a forest as a whole, if the forest in total is not growing, then it means that the new growth much be balanced out by the number of trees that die (just as when you look at human populations, there are always babies being born, but if the population as a whole does not grow, then it must mean that the number of people dying must be as many as the number of babies being born). The dying trees (unless they are somehow preserved - e.g. in a peet bog, or used in construction timber) will use up oxygen, and this will then balance the new oxygen being produced by the fresh growth.
George
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The irreversable effects of burning the trees and the fires that happen and exhaughst ect...is that the co2 stays in the atmospher for decades even up to a thousand years...we are still breathing a part of the first T- Model cars....Has anyone watched the prgram on discovery channel called "Global warming: What you need to know" ? It is kinda disturbing...
k