Comment by AngryData

It does take considerable energy to capture and store that carbon when it is only a small fraction of the atmosphere. Trees may not be as energy efficient as us building a dedicated process for it, but growing trees is basically free and it isn't like we are lacking land area to do so. Farmland utilization has been dropping for many decades all across the globe, and even if that didn't happen we would still be very far from running out of suitable tree growing land since trees can grow everywhere but the harshest deserts.