The issue is water and sand. While it's currently supplementing other ecosystems with nutritions, these by themselves won't magically become greenery.
It would definitely have an incredible effect on the climate if you could magically make Africa into a Forest again though. Might even make some parts of Europe uninhabitable with that cooling alone. Not gonna happen though.
> The issue is water and sand. While it's currently supplementing other ecosystems with nutritions, these by themselves won't magically become greenery.
photosynthesis efficiency goes up as CO2 increases, and plants need way less water.
This leads to greening of the entire planet and reversing desertification.
But at the same time, heat reduces photosynthesis efficiency, and even if it didn't, photosynthesis alone doesn't lead to healthy plants. You can't take one element in isolation.
