Captain Drawdown’s daily logbook on every CDR story, paper, and expert voice — so you don’t have to read them all.
The critique
“One mature tree takes up ~25 kg of CO₂/year, so 100 million trees will take up 2.5 MtCO₂. That’s a time machine that takes us back ~33 minutes in a year. Nature will not save us from fossil fuel CO₂.” That is David Ho (@davidho.bsky.social), and it is the cleanest attack on nature-based removal in circulation right now.
The framing is not that trees are bad. It is that the math is off by orders of magnitude relative to the regulatory weight forest credits carry on compliance markets.
The evidence Ho is reading correctly
Ho’s critique landed the same week as a Nature study showing US Forest Service buffer pools are far too small for the climate risks already in the pipeline. The buffer pool is the insurance mechanism. Under California Air Resources Board (CARB) Compliance Offset Protocol §95983, forest projects contribute a fraction of credits to a pooled reserve that is supposed to cover reversals from fire, drought, and pest outbreaks for 100 years. The Nature analysis says the contribution rates are structurally undersized. Reversals will exceed the reserve. The permanence promise breaks at exactly the wrong moment for compliance buyers.
Ho’s underlying argument from his 2023 Nature comment is that conflating short-lived biological storage with durable CDR misallocates buyer dollars and policy attention. The buffer-pool failure is the regulatory mechanism by which that misallocation gets exposed.
The community’s standard response, and where it is weak
The usual rebuttal runs: trees are co-benefits, scale will come, and durable removal is too expensive today. The weak point is that none of those defenses address Article 6.4 of the Paris Agreement, the EU Carbon Removals and Carbon Farming Regulation (CRCF), or CARB’s protocol updates, all of which now require permanence tiering. When the regulator separates durable from non-durable tonnes by rule, the parity pricing that subsidized forest credits ends. Co-benefits do not show up on a CORSIA invoice.
What the critique gets right
The arithmetic. The buffer math. And the regulatory seam. CarbonMeld documents the traceability gaps that let weak-permanence credits move freely between voluntary and compliance regimes. Heatmap’s reporting on GHG Protocol whistleblowers suggests the body writing corporate accounting rules may not fix what the buffer-pool study exposes. Ho is pointing at a real hole, and the regulator of last resort may be captured.
We made a version of this argument ourselves in Why Carbon Removal Needs More Than Trees.
What the critique misses or overstates
Two things. First, the 33-minute framing compares one project against annual global emissions. That is rhetorically sharp but it understates what a properly insured, properly stacked reforestation portfolio can do for land-sector accounting under LULUCF (land use, land-use change and forestry) reporting. Trees are not CDR at fossil scale. They are still useful inside national inventories.
Second, the critique implies durable removal is ready to absorb the demand that flees forest credits. It is not, yet. Chris Bataille (@chrisbataille.bsky.social) steelmans the destination: “That’s likely what CDR will mostly be; crushing the right rocks and dumping them in the ocean to carbonate.” ERW (enhanced rock weathering) and OAE (ocean alkalinity enhancement) are where the durable portfolio is heading, but TRL (technology readiness level) and supply are still constraints.
The synthesis
Pembina Institute (@pembina.org) notes: “Aviation is one of the hardest sectors to decarbonize, and among the first to get carbon removal off the ground.” Under CORSIA Phase 2 rules from 2027, airlines facing real residual emissions are already reaching for durable tonnes. The market is pricing Ho’s critique ahead of the regulator.
What CDR builders should take from this: watch whether CARB’s next Forest Offset Protocol update or the EU CRCF’s permanence tiering cites the Nature buffer-pool literature directly. That citation will mark the moment forest credits are formally repriced against durable removal. Every corporate net-zero plan built on cheap forest tonnes needs a Plan B inside 18 months. The durability premium stops being a marketing slide and becomes a regulatory floor.
CDR remains for hard-to-abate residual emissions only. Ho is right about that, too.
Citations
- Bluesky — @davidho.bsky.social — Bluesky post
- Nature — Nature study showing US Forest Service buffer pools are far too small for the climate risks already in the pipeline — research paper
- Nature — his 2023 Nature comment — research paper
- Carbonmeld — CarbonMeld documents the traceability gaps
- Heatmap News — Heatmap’s reporting on GHG Protocol whistleblowers
- Bluesky — @chrisbataille.bsky.social — Bluesky post
- Bluesky — @pembina.org — Bluesky post