A new study of trees from the journal Science indicates that added trees could store 830 billion tons of CO2. The world has room for 900 million hectares of trees. This would be over 1 trillion trees added to the existing 3 trillion trees.
The additional trees could be cut down in 20 years and the wood stores the CO2 unless they decay or are burned. Another batch of trees could be grown. If a breed of faster growing trees are used then every 12-15 years a batch of a trillion trees would offset all of the CO2 produced by civilization.
The best (non-drone) tree restoration projects are restoring billions of trees at 30 cents a tree. This means 1 trillion trees would be $300 billion. Drone planting of trees can use 4000 drones, and 2000 people to plant 10 billion trees per year at about $1 billion per year.
It might be triple this amount to cut down the trees and to use the wood. The value of the wood could offset the cost of cutting them down. A very rough estimate would be $450 billion every 12 years to cut plant and cut down some faster-growing trees to offset all human CO2 and greenhouse gas production.
The researchers claim it is not a complete solution. However, if we stabilize the growth of CO2 production which is affordable and then cut down the trees every 12-20 years to sequester a fresh amount of CO2 then it is a complete solution.
The three other solutions that scale are regenerative agriculture to restore top soil, iron fertilization of the ocean and mass production of kelp at 1000 times current levels.
Most of the land suitable for restoring forests trees is in six countries —
Russia (151 million hectares),
USA (103 million hectares),
Canada (78 million),
Australia (58 million),
Brazil (50 million), and
China (40 million).
The potential for global forest cover
The restoration of forested land at a global scale could help capture atmospheric carbon and mitigate climate change. Bastin et al. used direct measurements of forest cover to generate a model of forest restoration potential across the globe (see the Perspective by Chazdon and Brancalion). Their spatially explicit maps show how much additional tree cover could exist outside of existing forests and agricultural and urban land. Ecosystems could support an additional 0.9 billion hectares of continuous forest. This would represent a greater than 25% increase in a forested area, including more than 500 billion trees and more than 200 gigatonnes of additional carbon at maturity. Such a change has the potential to cut the atmospheric carbon pool by about 25%.
The researchers used Google Earth to see what areas could support more trees, while leaving room for people and crops. Lead author Jean-Francois Bastin estimated there’s space for at least 1 trillion more trees, but it could be 1.5 trillion.
They mapped the global potential tree coverage to show that 4.4 billion hectares of canopy cover could exist under the current climate. Excluding existing trees and agricultural and urban areas, they found that there is room for an extra 900 million hectares of canopy cover, which could store 205 gigatonnes of carbon (3.67 times this weight to get CO2. CO2 molecular weight is 44 versus 12 for carbon) in areas that would naturally support woodlands and forests. This highlights global tree restoration as our most effective climate change solution to date. However, climate change will alter this potential tree coverage. The global potential canopy cover may shrink by ~223 million hectares by 2050, with the vast majority of losses occurring in the tropics. The results highlight the opportunity of climate change mitigation through global tree restoration but also the urgent need for action.