Why Planting Trees Won't Save the PlanetArchived Message
Posted by scrabb on October 5, 2019, 2:25 pm
LRB Vol. 41 No. 19 · 10 October 2019
Our Alien Planet Don Lock reproaches Francis Gooding for failing to see trees as a ‘carbon capture technology’ (Letters, 12 September). He’s right in principle. Through photosynthesis, plants of every kind, from grass to redwoods, convert carbon dioxide in the atmosphere into bulk matter: the majority of the mass of any plant is carbon captured from the air. A plant is however only a temporary store of carbon, since that carbon will be released directly or indirectly into the atmosphere when the plant is consumed by animals, or dies and decays, or is otherwise disposed of. A forest is a large, temporary carbon store, in a dynamic equilibrium between growing trees and decaying or harvested trees; burning, and other forms of destruction, release that carbon ahead of schedule.
The point of carbon capture and sequestration (CCS) is to prevent a store from ever releasing its carbon. For trees, that would mean burying them deep beyond the reach of oxygen for a few thousand years, and planting replacements. Broadly, sequestered carbon is buried carbon, and the cause of our climate problems is our diligent unsequestering of carbon through its transformation into coal, oil and gas, which last saw daylight in the Carboniferous period.
What would this mean in practice? Even if we buried 10 per cent of the trees on the planet (10 per cent of about 422 gigatonnes of wood worldwide), we would roughly match only a year’s worth of CO2 emissions at 2017 rates. This would be at the cost of an epic expenditure of energy – and we would need to repeat the process every year. CCS (not involving trees) is not fundamentally implausible. But it is expensive, speculative, and designed to reduce industrial emissions, rather than remove carbon in bulk from the air.