Phew, it took more than two years for Nature to publish our critique of the Peng et al. no harvest counterfactual approach to assess the carbon implications of wood harvesting. The long delay was due to the time it took Tim Searchinger and Steven Berry, who was not originally an author on the Peng et al. paper, to write, revise, talk to reporters, and revise their reply some more.

The 2500-word reply, with 29 citations and two supplements, not only dwarfs our 1200 words, 15 cites and no supplement (Nature wouldn’t allow us), but it is also a classic diversion tactic. Our Matter’s Arising critique illustrated key problems with Peng et al stemming from basic forestry, economics, and common-sense. Their response is about parameters in a different model that has nothing to do with the failures of their approach.

What they want to have is a conversation about anything but their own model.  I’m happy to have a conversation with them, but the only people they talk to seem to be themselves and the press.

In summer 2024 when they planned to publish their online hit piece about the Global Timber Model (GTM) through the World Resources Institute (WRI), I got bunches of emails from reporters asking me to comment on GTM because Searchinger and Berry had sent their piece to reporters who liked them before they published it. The were most interested in using the press to attack GTM.

Some of those reporters talked to me. Some didn’t bother.

I subsequently emailed Searchinger and Berry to see if they wanted to do a joint public webinar on carbon accounting for wood products. It would be an opportunity to talk about both our models, clarify similarities and differences in approach and parameters, and hopefully find some common ground.

They never responded.

But they did spend the last 12 months making virtually no changes to their response to our critique, which is what slowed the process of getting the thing published. You can see documentation of all this in my correspondence with Searchinger, Berry, and Nature, including the reviews and our responses, on this Dropbox site. We have asked Nature to provide the entire review record online, but have not gotten them to do that, yet.

Funny thing is, WRI seems all in on this insular approach to science. When Searchinger and Berry published their hit piece in 2024, I asked WRI if they would publish our response. They declined. Rather than hosting a joint webinar, last week, WRI held a webinar hosted by their Head of Communications Andrew Marshall featuring only Searchinger and Berry.

Honestly, it was a humbling and spooky webinar. The humbling part was me realizing I was living rent free in their heads. How else to explain one hour by such eminent people devoted to eviscerating  me and GTM? The spooky part was I was like ghost floating around the event. Even when they managed to obliquely address one of the questions I directly asked in the Zoom Q&A, they wouldn’t say my name or even post any of the questions I asked publicly.

Regarding their reply to our Matter’s Arising critique, there are some serious things to address. These relate to their responses to our comment, not to their critique of GTM. We address the GTM critique here.

First, I don’t think Searchinger and Berry understand the concept of sustained yield in forestry. If you take a forest that is economically optimally managed with harvests occurring at 30 years of age and move it to say a 35- or 40- year rotations, annual output will increase in the long run and the stock on the site will increase. This means you can have more wood output and remove some carbon from the atmosphere without changing forest area (which is their main complaint about GTM). Deferring wood harvests can increase carbon storage and output over time.  This is not a GTM result, as they suggest, it is a forestry result.

Second, driving cars proves nothing, unless you are driving to a forest for a hike, in which case I hope you ride your bike so you don’t have to debate these smart people about whether it is credible to argue that 50 miles per gallon is better than 20 miles per gallon for that trip from the perspective of the atmosphere.

Simply stated, vast emissions don’t disappear in any forestry model I know, including my own, that does carbon accounting. Rather than writing about cars, which I understand is a thing, maybe we should all read the forestry literature. Carefully.

Third, in the “The Fallacy of Inherent Carbon Neutrality” section, Searchinger et al. are creating a dog’s breakfast of confusion over something that is not confusing. People plant forests, manage forests, and cut them down. They should get credit for the things they do.  As we describe, CHARM vastly underestimates this credit because they count it only after the fact of harvesting, not before.

There is nothing complicated about that. Peng et al create an accounting stance that counts regrowth after harvesting and discounts it to get the largest emission calculation they can get. We say trees didn’t just appear out of nowhere to be harvested, so you should count the gains from management and planting and growing that happened before harvesting.

Searchinger, Berry and Peng are clever to try to include the CO2 and climate change arguments, but this isn’t about passive carbon accumulation. This is about two different accounting stances. If you are someone who doesn’t want to credit other humans with their own cleverness at figuring out how to grow and manage trees effectively, then you’ll go with the Searchinger, Berry, and WRI no harvest counterfactual approach. Otherwise, you’ll use IPCC/UNFCCC accounting.

Fourth, when I get to the “Landscape-scale accounting” and “Planted Forests” sections of the reply, I admit my head is spinning.  On the landscape issue, I thought Searchinger understood the need for market-based analysis because of his earlier highly cited piece in Science that use a market model with land supply functions to argue biofuel subsidies in the US would lead to deforestation in the Amazon. But I guess now he believes it’s ok to model each place in the world independently without worrying about knock-on effects? As noted, I’m confused.

Regarding planted forests, this is what we wrote “In the absence of markets, the proper counterfactual for planted stands is either no stand at all or a naturally regenerated stand with less carbon at the same age or on average in some places.” You can be the judge as to whether they read our response.

Finally, we get to the meat of their argument in the section “Do economic responses offset emissions from wood demand?” This is their screed on GTM, to which we have already responded in this SSRN paper.

Note that we do not state what economic model should be used to properly do the analysis Peng et al. try to do. We simply claim that Peng et al. ignore supply side factors, like costs and interest rates, when they determine what gets harvested. This is a low credibility threshold, which their model does not meet.

I get pointing out that someone else’s parameters may be wrong. GTM modelers have learned from that over the years and adapted our model. I don’t get the hubris of ignoring marginal costs entirely. In GTM when you harvest trees, you only replant on that site if the present value of projected timber revenues exceed the costs of planting and renting the land. In CHARM, it is free to plant and maintain forests. Utopian, perhaps, but unrealistic.

In conclusion, consider this quote from Searchinger, Berry, and Peng: “And credible economic counterfactuals for policy cannot be made by layering assumed parameters on assumed functions, because others could just assume something different.” I know this is serious stuff, but it’s just not possible to make this stuff up. If you’ve made it this far, have a good laugh.  You deserve it.