Can planting billions of trees save the planet?

Unfortunately the billions of trees provide only a one off benefit. Once they die and rot away the carbon is released back again. So you either need to prevent that carbon ever getting back into the atmosphere or ensure those forests are sustained forever. A useful approach to getting some carbon out of the atmosphere but we still need to stop releasing carbon.

At the title, I don't think the planet need to be saved. We/They are saving ourself/theirself.