I have not looked at this deeply, so take all of this with a grain of salt, but a quick scan makes me believe that this is very hyped.
Having skimmed the paper it seems the only thing the authors do and what is peer-reviewed is estimate earth’s theoretical maximum capacity for reforestation.
There are few problems:
1) Feasibility: “200 GtC is a technical potential assuming every hectare of forestland on earth is increased to 100% forest cover”
“An assessment of the biophysical capacity for restoring global tree cover provides a necessary but insufficient foundation for evaluating where tree cover can be feasibly increased. The kinds of trees as well as how and where they are grown determine how and which people benefit. In some contexts, increasing tree cover can elevate fire risk, decrease water supplies, and cause crop damage by wildlife. Reforestation programs often favor single-species tree plantations over restoring native forest ecosystems. This approach can generate negative consequences for biodiversity and carbon storage (5), threaten food and land security, and exacerbate social inequities. How restored lands are governed determines how reforestation costs and benefits are distributed.”
There are no dollar signs or economic feasibility analysis in that paper. So the people who wrote it just cited some number that is not peer-reviewed and even if loosely based on previous numbers might not work at the scale.
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2) There seems to be no scientific consensus how much (or even if!) new trees are a GHG sink on net. Some legitimate papers even suggests that new trees could be a net GHG source. (the paper does not make any new contributions to this question and I think just assumes that trees absorb GHG).
For instance, see this recent paper in Nature communications:
b) this recent paper in PNAS (top journal as well)
“On-going carbon uptake due to forest demography is large, but much smaller than previous influential estimates have suggested. Contrary to previous findings, these latest data sources indicate that the sink is predominantly in mid-high latitude, rather than tropical, forests.”
I have not looked at this deeply, so take all of this with a grain of salt, but a quick scan makes me believe that this is very hyped.
Having skimmed the paper it seems the only thing the authors do and what is peer-reviewed is estimate earth’s theoretical maximum capacity for reforestation.
There are few problems:
1) Feasibility: “200 GtC is a technical potential assuming every hectare of forestland on earth is increased to 100% forest cover”
https://twitter.com/hausfath/status/1147190442145898496
“An assessment of the biophysical capacity for restoring global tree cover provides a necessary but insufficient foundation for evaluating where tree cover can be feasibly increased. The kinds of trees as well as how and where they are grown determine how and which people benefit. In some contexts, increasing tree cover can elevate fire risk, decrease water supplies, and cause crop damage by wildlife. Reforestation programs often favor single-species tree plantations over restoring native forest ecosystems. This approach can generate negative consequences for biodiversity and carbon storage (5), threaten food and land security, and exacerbate social inequities. How restored lands are governed determines how reforestation costs and benefits are distributed.”
https://science.sciencemag.org/content/365/6448/24
There are no dollar signs or economic feasibility analysis in that paper. So the people who wrote it just cited some number that is not peer-reviewed and even if loosely based on previous numbers might not work at the scale.
--
2) There seems to be no scientific consensus how much (or even if!) new trees are a GHG sink on net. Some legitimate papers even suggests that new trees could be a net GHG source. (the paper does not make any new contributions to this question and I think just assumes that trees absorb GHG).
For instance, see this recent paper in Nature communications:
a) “Limited capacity of tree growth to mitigate the global greenhouse effect under predicted warming” https://www.nature.com/articles/s41467-019-10174-4
b) this recent paper in PNAS (top journal as well)
“On-going carbon uptake due to forest demography is large, but much smaller than previous influential estimates have suggested. Contrary to previous findings, these latest data sources indicate that the sink is predominantly in mid-high latitude, rather than tropical, forests.”
https://www.pnas.org/content/116/10/4382.short
2) is great stuff, thanks for posting it.
Have some disagreements with 1 because there is no possible intervention that can’t be made infeasible with enough impact report requirements.