What's Wrong With The Trillion Tree Plan? Pretty Much Everything, As It Turns Out
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Take the trees thing. The scientists who proposed it made careful maps of where trees grow today, all over the planet. They had a census of how many were there, combined with satellite data, all used to estimate how many potential trees could grow—and how much carbon those trees would slurp out of the atmosphere, a nontrivial calculation. There’s room for 0.9 billion hectares of new trees, they said—2.2 billion acres of tree cover, which draws down 205 metric gigatons of carbon, or 225 billion tons in US non-metric. That’s in line with the goal of keeping warming at or below 1.5 degrees, per the Intergovernmental Panel on Climate Change. World: saved!
But then the bills started coming due. The team forgot that 55 percent of all historically emitted carbon got absorbed by the oceans, not the land, and so underestimated the total amount of carbon by about one half. They overestimated carbon uptake by trees, and suggested putting trees where they’ve never been, or where they’d actually make the planet hotter (by darkening planetary albedo over icy, more reflective terrain). They didn’t take into account that the ecosystems where they wanted to plant trees already sequestered carbon. And so on. “We’re not talking about small errors here. We’re talking about a huge difference in the total amount of carbon you could sequester,” says Carla Staver, an ecologist at Yale University.
The lead scientist and the person who runs the lab that produced the initial paper didn’t respond to my requests for interviews, but in response to the criticisms in Science they wrote: “We intended to highlight that we are aware of no other viable climate change solution that is quantitatively as large in terms of carbon drawdown. We did not suggest that tree restoration should be considered as the unique solution to climate change.” They broadly stuck to their numbers, or said their critics had misinterpreted or misread them. But mostly, the implication was, hey, come on! We’re all in this together. Which is true, as far as that goes. But if scientists get it wrong, the fight could fall apart—or become an easier target for climate deniers who already see conspiracies behind every scientific warning. “All of those technical responses were written by people who believe there is a place for forest restoration in mitigating climate change and emissions,” Staver says. “It behooves us as scientists to be realistic about how much that’s going to get us. We have to make good faith estimates.”
The same thing is happening with the Terraton Initiative. The company behind it, Indigo, is a startup trying to promulgate regenerative agriculture—methods like relying on perennials instead of annually replanted species, or cover crops to reduce the need for tilling. “We’re encouraging farmers to use less fertilizer, fewer chemicals, and data science and microbiology to improve yield, and get paid a premium for growing things more sustainably,” says David Perry, Indigo’s CEO. Terraton launched last June; sign up, and you get $15 for every ton of carbon sequestered, measured through regular tests of soil health. (Hey, wait, doesn’t that mean the startup would need to pony up $15 trillion? The cash, the company says, will come from Indigo’s venture money, and eventually from a carbon market that’ll sell offsets or use government subsidies, should such a thing ever exist.) Perry says they expected to have 3 million acres signed up in the first year, and instead they have 10 million acres in the first 100 days. World: saved!
Except, well, math. One 2017 study of 150,000 sample points all over Earth said that since the advent of agriculture, we’ve lost about 133 billion tons of carbon from the ground. Several analyses of carbon sequestration efforts estimate that with current limitations and in the best case scenario, we’ll only likely to recover about 50 or 60 percent of this lost carbon. “There’s a community of scientists who’ve been working on these issues for the better part of 20 years and who’ve published numerous papers showing what the soil potential of the planet would be, and Indigo chose to ignore those,” says Jonathan Foley, an environmental scientist and executive director of the climate change-fighting group Project Drawdown. “I just have to scratch my head and ask why they’re doing that.”
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https://www.wired.com/story/trees-regenerative-agriculture-climate-change/
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