Deforestation

[howelli]

Apart from the devastating loss of species and natural wonder, could anyone calculate the amount of O2/CO2 produced and consumed by a) a unit surface area of rain forest and it's inhabitants and b) the same area substitued with grass, cattle and it's other resulting inhabitants? 

[jake-the-peg]

If only it were that simple.

Trees also respire, (take in Oxygen and produce CO2) as well as photosynthesise and mature trees do this a lot.

There was a concept a few years back of "carbon sinks" (check google carbon sinks and IPCC [ Inter governmental panel on Climate control ]) that basically said all we needed to do was plant a lot more trees. It soon became clear that after a few years these carbon sinks would become saturated and actually start putting CO2 back into the atmosphere.

I believe the biggest contributer to carbon removal from the atmosphere is phytoplankton in the oceans and that the rainforests have a reasonably small overall effect.

[Clanad]

Actually, trees utilize transpiration, (through photosynthesis) and they take in carbon dioxide and give off oxygen... In fact it's estimated the rain forests produce nearly 40% of the earth's oxygen supply.

Rainforest trees have leaf surface areas that run as high as forty acres per tree. Throughout this enormous surface area, sunlight is used as an energy source to drive the conversion of carbon dioxide into oxygen and plant matter (using the �C� which is carbon). Trees literally breathe in the CO2 through that enormous leaf area after we exhale it as biological waste, and they exhale oxygen as their own waste.(Source Blue Planet Biomes). I've not found statistical data on how much 1 tree or one acre produces which is needed to answer your question accurately...

[brachiopod]

But they only do this during daylight, clanad.

The Calvin Cycle - the process of a plant's respiration -actually uses oxygen and releases carbon dioxide. This occurs continuously day and night, (and hence is often called the 'dark reaction'). Since photosynthesis does not occur at night, there is actually an (albeit small) net loss of oxygen during the hours of darkness.

[Clanad]

Thanks, brachiopod! Is it not true that the Light Phase Reactions (Z Scheme) requiring sunlight and Dark Phase Reactions (Calvin Cycle) not requiring light, are each part of the entire cycle?  Light Phase Reactions producing high energy ATP and NADPH molecules with the Dark Phase releasing energy and converting them back to depleted ADP and NADP and in the process synthesizes glucose and other carbohydrates. I think it's the process that, then simultaneously releases oxygen into the atmosphere. This photosythensis powers the plant and does, overall produce a surplus of oxygen...

[jake-the-peg]

Surely land based plants will only ever remove carbon from the atmoshere in order to grow.

When they die they rot and the carbon is re-released they'll only trap carbon in the earth if they get trapped in a coal or peat forming geology.

The food cycles in marine systems will end with carbon based detritus falling to the ocean bed.

All the same it seems that both marine and land based systems will react badly to rising temperatures. There's this issue

http://www.abc.net.au/catalyst/stories/s1058761.htm

with rainforests releasing CO2 under stress and in the marine side CO2 absorbtion drops with increasing temperature.

Don't get me wrong though with a climate that's changing performing global ecology changes like deforestation is tantamount to playing russian roulette.