"The fact that they aren't using this adaptation (or some other one) means that probably photosynthesis speed is already being traded off against some other fac

"The fact that they aren't using this adaptation (or some other one) means that probably photosynthesis speed is already being traded off against some other factor in their communities" What's best for the tree might not be best for us. Human civilization is in a time and resource crunch. This isn't about making better trees for trees sake, this is about solving the immediate problem of too much carbon in the atmosphere. I'll give you though, that once we solve this carbon problem it's possible we might have another problem. So hopefully we keep a backup of some of these "heritage" trees.