What?! Dude, plants grow by taking carbon dioxide from the air, and water, converting it to carbon and hydrocarbons (the growing plant) and oxygen (released back into the air). The using of carbon dioxide and releasing of oxygen is why forests are called the lungs of the world, and why the air smells so fresh in a forest. When plants burn, the carbon and hydrocarbons (that are the plant) combines with oxygen in the air and produces carbon dioxide and water vapour.
Animals and humans, on the other hand, breathe in air and use the oxygen in it to oxygenate the blood. Thus why if you're stuck in a small room with closed windows and doors for a while, the air becomes stuffy from al the oxygen being depleted. One easy way to sleep better - have indoor plants in your bedroom.
So if the world is covered in forests, then there is a lot of oxygen and fresh air. If we burn down the forests to use for grazing lands, then there will be a lot less oxygen, and a lot more carbon dioxide in the air, which is a greenhouse gas, which will contribute to global warming.
The science of this is simple, well known, and well beyond doubt. Unfortunately, there are a bunch of issues, such as: there are a handful of billionaires making good profits from fossil fuels and from replacing rainforests with grazing lands, and they are making hay while the sun shines, and to prolong it, are filling the world with misinformation so that the common man is confused about if global warming is real or not; also no-one really knows quite how bad the consequences will be, because the world has never experienced man-made global warming before, so the modelling is difficult; and also with the fact that the change is gradual, so it doesn't feel quite real, even though year after year there are more record hot temperatures being broken; and also the fact that right aligned people are more about personal responsibility, and left aligned people are more about collective responsibility, and because global warming requires collective responsibility more than personal responsibility to fix it, the left are the first to want to act, and this makes a lot of people on the right see the problem as a politically motivated lefty thing rather than a real problem; and thus, all that combined, the result is a lot of fear, uncertainty, and doubt. The big problem with this is, global warming is likely to accelerate and be beyond the point of repair by the time there is enough people wanting to fix it.
