[midoridensha]

>Trees weren't designed to capture carbon, so there's every reason to think something which is can do a better job.

They weren't, but just like jets and knives require a lot of human labor to manufacture in mass quantities, any artificial solutions are likely to be the same for a while. Trees, on the other hand, are fully automatic, self-replicating machines that require almost no human labor (perhaps for initial plantings in a place where they don't already grow, or don't grow in sufficient quantities with their natural self-replication). Basically, if you plant a bunch of tree saplings somewhere suitable, you can leave it alone for 300 years and come back and find a forest.