Investment managers who have bought up forestland are going tree by tree to figure out whether they should be felled for timber or kept up for carbon-credit generation. Growing demand for credits means investing in forests isn’t just about producing timber, but it can take a lot of legwork to determine what role each tree should play in a portfolio, as well as ensure it is delivering its promised environmental benefit if left standing. …Manulife, which has 5.4 million acres of forest in its investment portfolio, calculates the value of each tree to inform its harvest strategy. Every tree in a forest has to be evaluated based on species growth rates and product value. If the carbon credit value is high enough, it stays up even if for just a few more years. If not, it’s cut down for timber. …Kernohan said that until recently, forest land wasn’t valuable enough to be considered. [to access the full story a WSJ subscription is required]