# O2, CO2 and Living Beings? **URL:** \ **Category:** Factual Questions\ **Created:** [March 7, 2004, 6:49am UTC](https://boards.straightdope.com/t/o2-co2-and-living-beings/232953 "2004-03-07T06:49:04Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![SwingWing](https://avatars.discourse-cdn.com/v4/letter/s/a3d4f5/32.png) [@SwingWing](https://boards.straightdope.com/u/SwingWing)\ **Post date:** [March 7, 2004, 6:49am UTC](https://boards.straightdope.com/t/o2-co2-and-living-beings/232953/1 "2004-03-07T06:49:04Z")
Most living beings consume O2, converting it to CO2. Trees and plants convert CO2 to O2. If all the rain forest and trees have been destroyed, to the extent represented, and greenhouse effects of CO2 is such a problem, why hasn’t the population of living beings, particularly human beings, been significantly reduced? ---
**Author:** ![choosybeggar](https://avatars.discourse-cdn.com/v4/letter/c/8c91f0/32.png) [@choosybeggar](https://boards.straightdope.com/u/choosybeggar)\ **Post date:** [March 7, 2004, 6:53am UTC](https://boards.straightdope.com/t/o2-co2-and-living-beings/232953/2 "2004-03-07T06:53:37Z")
> [@SwingWing](#): > > Most living beings consume O2, converting it to CO2. Trees and plants convert CO2 to O2. If all the rain forest and trees have been destroyed, to the extent represented, and greenhouse effects of CO2 is such a problem, why hasn’t the population of living beings, particularly human beings, been significantly reduced? The atmosphere is big and contains a high proportion of oxygen (21%) and a low proportion of CO2 (less than 1%) We need lower O2 or higher CO2 levels to die. ---
**Author:** ![Really\_Not\_All\_That\_Bright](https://avatars.discourse-cdn.com/v4/letter/r/e8c25b/32.png) [@Really\_Not\_All\_That\_Bright](https://boards.straightdope.com/u/Really_Not_All_That_Bright)\ **Post date:** [March 7, 2004, 8:12am UTC](https://boards.straightdope.com/t/o2-co2-and-living-beings/232953/3 "2004-03-07T08:12:16Z")
> [@SwingWing](#): > > Most living beings consume O2, converting it to CO2. Trees and plants convert CO2 to O2. If all the rain forest and trees have been destroyed, to the extent represented, and greenhouse effects of CO2 is such a problem, why hasn’t the population of living beings, particularly human beings, been significantly reduced? Because nothing is _killing_ them. Think of it like the economy. Taxes are X. Government spending is Y. If the budget is balanced, X=Y. If, then, government increases spending, Y\>X That doesn’t mean the economy collapses, though. It doesn’t necessarily mean that X increases to match Y. In fact, it hardly ever means that: see Federal debt. The system can continue to operate even though it isn’t balanced; it just can’t operate like that forever. You don’t need a lot of CO2 to cause a greenhouse effect. You need a little CO2, and a little methane and other greenhouse gases. CO2 makes up less than 1% of the atmosphere. ---
**Author:** ![RandomLetters](https://avatars.discourse-cdn.com/v4/letter/r/8edcca/32.png) [@RandomLetters](https://boards.straightdope.com/u/RandomLetters)\ **Post date:** [March 7, 2004, 11:05am UTC](https://boards.straightdope.com/t/o2-co2-and-living-beings/232953/4 "2004-03-07T11:05:11Z")
I would also like to note that the rainforest/trees are not the main source of oxygen - marine plants, especially algae, are, producing [[www.ecology.com/dr-jacks-natural-world/most-important-organism/+ocean+algae+oxygen&hl=en&ie=UTF-8](http://www.ecology.com/dr-jacks-natural-world/most-important-organism/+ocean+algae+oxygen&hl=en&ie=UTF-8)]between]([http://216.239.57.104/search?q=cache:SbUzcwMBtSAJ:](http://216.239.57.104/search?q=cache:SbUzcwMBtSAJ:)[url) 70%-80% of the worlds oxygen. And there is some controversy on whether rainforest actually produce any net oxygen at all. ---
**Author:** ![RandomLetters](https://avatars.discourse-cdn.com/v4/letter/r/8edcca/32.png) [@RandomLetters](https://boards.straightdope.com/u/RandomLetters)\ **Post date:** [March 7, 2004, 11:11am UTC](https://boards.straightdope.com/t/o2-co2-and-living-beings/232953/5 "2004-03-07T11:11:59Z")
Sorry about the screwed up link there - [ecology.com](http://ecology.com) wasn’t working, so I tried to link a google cache. ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [March 7, 2004, 1:43pm UTC](https://boards.straightdope.com/t/o2-co2-and-living-beings/232953/6 "2004-03-07T13:43:39Z")
And don’t forget that most of the oxygen in the atmosphere was put there long ago by long dead plants; if you killed all the plants in the world and converted their carbon into CO2 the oxygen level of the atmosphere would only go down by a few percent- so oxygen does not have to be constantly replenished on our planet. A surfeit of carbon dioxide however would have a marked effect on the climate and particularly the world temperature. ---
**Author:** ![Joe\_Random](https://avatars.discourse-cdn.com/v4/letter/j/e8c25b/32.png) [@Joe\_Random](https://boards.straightdope.com/u/Joe_Random)\ **Post date:** [March 7, 2004, 3:24pm UTC](https://boards.straightdope.com/t/o2-co2-and-living-beings/232953/7 "2004-03-07T15:24:16Z")
> [@SwingWing](#): > > Trees and plants convert CO2 to O2. This is only true during the day, when they’re undergoing photosynthesis. At night, plants convert O[sub]2[/sub] to CO[sub]2[/sub]. Meaning that a full-grown plant does not change the amount of O[sub]2[/sub] or CO[sub]2[/sub] in the atmosphere. However, _growing_ plants consume more CO[sub]2[/sub] than they produce, because they are using CO[sub]2[/sub] for its carbon in order to build things like cell walls.