"Just because carbon dioxide is food for plants doesn't mean plants can deal with excess."
Why don't you explain at what level Co2 is excessive to plants. You do realise that we are at one of the lowest Co2 levels in the worlds history.
Fact is that CO2 levels today are barely enough for plants, they grow better and need less water at higher concentrations and greenhouse farmers raise it artificially. They would hardly do so if we were entering the toxic range of CO2 naturally now would they? There would be no point is searching for a reference because it won't be on an approved "green" site and any other would be dismissed as "discredited already".
The only down side I've read is that the quality of some timber suffers if the tree grows too quickly, but we aren't allowed to harvest them anyway.
And another thing: Satellite imagery shows increasing timbered areas around the world already. That's a good thing isn't it?
