Comment Parent is right (Score 4, Informative) 141
Too bad this is getting downvoted as it is correct. Trees consume very little of the CO2 we produce from fossil fuels, in part because trees themselves produce enormous amounts of CO2 every night, which they then re-absorb during the day.
The vast majority of CO2 fixing occurs in the ocean, not the forest.
NARRATOR: So dense is the Amazon jungle that it has a dramatic impact on the air above it. It starts in the trillions of leaves far below.
We can use animation to show what this invisible process, known as photosynthesis, might look like. During the day, the leaf takes up carbon dioxide from the air, seen here in orange. It converts the carbon into sugar and releases the gas that allows us to burn our fuel, oxygen, seen in blue.
Each one of these trees will release hundreds of thousands of cubic meters of oxygen in the course of its life. And as for the Amazon as a whole, a fifth of the world's oxygen is produced here. But here's the surprise: we will breathe almost none of it. Satellite data and ground measurements reveal that almost all the oxygen the Amazon produces during the day remains there and is reabsorbed into the forest at night.
PIERS SELLERS: With the advantage of the satellites, we can now see that the Amazon basically uses all its own oxygen and uses all its own carbon dioxide. It is, as far as we can tell, almost a closed system, in and of itself, almost.
Source: http://www.pbs.org/wgbh/nova/space/earth-from-space.html