Reforestation as a Solution for Carbon Capture: Hype and Reality

By Lambert Strether of Corrente

A new study from the Crowther Lab at the Swiss Federal Institute of Technology in Zurich published in Science (paywalled, but here is the original) has come out with a recommendation for reforestation as a (partial) solution to carbon capture. The report has gotten a lot of great press — “Stop building a spaceship to Mars and just plant some damn trees” is perhaps the most overheated headline, although the article is good — but there are issues. One issue is that the method of reforestation[1] — plantations or, for want of a better word, natural — matters. Finally, there are issues about how and where to appropriate the land, much of which is currently being deforested by powerful business concerns, and some of which is already occupied by indigenous peoples. Let’s look at each of these issues in turn, starting out with the Science report.

Carbon Saved by Reforestation

From the abstract, Jean-Francois Bastin, Yelena Finegold, Claude Garcia, Danilo Mollicone, Marcelo Rezende, Devin Routh, Constantin M. Zohner, Thomas W. Crowther, “The global tree restoration potential” (“Crowther”):

The restoration of trees remains among the most effective strategies for climate change mitigation. We 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, we found that there is room for an extra 0.9 billion hectares of canopy cover, which could store 205 gigatonnes of 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. We estimate that if we cannot deviate from the current trajectory, the global potential canopy cover may shrink by ~223 million hectares by 2050, with the vast majority of losses occurring in the tropics. Our results highlight the opportunity of climate change mitigation through global tree restoration but also the urgent need for action.

The following figure shows the mapping:

The caption for the figure:

Fig. 2. The current global tree restoration potential. (A) The global potential tree cover representing an area of 4.4 billion ha of canopy cover distributed across the world. (B and C) The global potential tree cover available for restoration. Shown is the global potential tree cover (A), from which we subtracted existing tree cover (15) and removed agricultural and urban areas according to (B) Globcover (16) and (C) Fritz et al. (17). This global tree restoration potential [(B) and (C)] represents an area of 0.9 billion ha of canopy cover (table S2).

Essentially, the study is an inventory using sophisticated GIS techniques.

Reforestation is a Partial Solution

250 gigatonnes is a lot; but for comparison, from

565 gigatons — Scientists estimate that humans can pour roughly 565 more gigatons of carbon dioxide into the atmosphere and still have some reasonable hope of staying below two degrees.

Since CO2 emissions are still rising, we could still run off the 546 gigatons runway, even if we could take 250 gigatonnes out of the equation instantly. (Forests take time to grow; even secondary forests in the tropics take a decade.)

So I find the excitability embodied in this tweet a little irritating:

Further, the Crowther abstract is carefully, even gingerly, worded:

..among the most effective strategies for climate change mitigation…

That does not say that reforestation is the best, or the only effective strategy[2]. Besides overexcitability, I’m irritated by our collective inability to integrate and sum a collection of strategies to bring us to the required total of reductions (among them necessarily industrial policy; see NC here).

Methods of Reforestation Matter

Although this issue is covered in Crowther, the nuance is lost in the press coverage. From Nature, “Restoring natural forests is the best way to remove atmospheric carbon

[P]lantations are much poorer at storing carbon than are natural forests, which develop with little or no disturbance from humans. The regular harvesting and clearing of plantations releases stored CO2 back into the atmosphere every 10–20 years. By contrast, natural forests continue to sequester carbon for many decades

Protecting land from fire and other human disturbances allows trees to return and forests to flourish, building carbon stocks rapidly to reach the level of a mature forest in roughly 70 years4. Recovery times can be accelerated by planting native species, and the area under natural regeneration expanded using legislation and incentives, such as those pioneered in Costa Rica.

However, plantations are the most popular restoration plan

In other words, if private equity goes into “reforestation”[3] in a big way — generating more overheated headlines like the one above — they’ll do so with plantations, because harvesting plantations generates profit. But profit should clearly not be the priority; meeting our carbon stock goals should be. Or so one would think.

Appropriating the Land for Reforestation

As the maps in the Crowther figure show, reforestation would take a lot of land:

In 2018, the United Nations’ Intergovernmental Panel on Climate Change, the world’s foremost authority on climate, estimated that we’d need to plant 1 billion hectares of forest by 2050 to keep the globe from warming a full 1.5 degrees Celsius over pre-industrial levels. (One hectare is about twice the size of a football field.) Not only is that “undoubtedly achievable,” according to the study’s authors, but global tree restoration is “our most effective climate change solution to date.”

(IPCC says 1 billion; Crowther confirms 0.9 billion. That’s about three times the size of India.)

Again, Crowther is aware of this, but it’s another nuance lost in the coverage. The methods that would most likely to be used to appropriate this land are uncomfortably close to the enclosures. See Kristen Lyons, “The new corporate enclosures: Plantation forestry, carbon markets and the limits of financialised solutions to the climate crisis” (PDF). From the abstract:

In recognition of the opportunities associated with climate change, the finance sector have engaged in market based activities via the acquisition of land for ecosystem services, such as biofuel production or forestry for carbon sequestration. Many of these investments are global in scope; with finance capital from the Global North directed into the acquisition of land in the global South. We take the case study of the self-proclaimed largest plantation forestry operator on the African continent, the Norwegian company, Green Resources and their Ugandan land acquisition, to explore, firstly, the claims-making associated with the expanding financialisation of land and natural resources and secondly, the new corporate enclosures engendered via such companies’ participation in the expanding carbon economy. Our findings show that investor claims regarding the economic development and environmental sustainability at the site level do not match with the lived reality of Ugandan villagers at the investment site. Whilst carbon capture is possible, it is outweighed by a suite of social and environment ills, including forced dispossession, biodiversity loss and chemical pollution.

In other words, if we use the market for an enormous real estate play to appropriate the necessary land, the process of appropriation will necessarily be financialized, with (a) attendant resistance, violence, inability to meet schedule, resulting in (b) plantations, rather than forests, leading to distinctly suboptimal suboptimal performance in carbon capture.


As so often, the really interesting problems are not technical in nature, but part of political economy, that is to say part of politics, both by the current owners of the land (indigenous or no), by policy makers in the First World, and by capital[3]. I hope to return to the topic of reforestation again with more than a mere sketch.


[1] Fascinatingly, reforestation is not all a new idea; see James B. Pollack and Carl Sagan in 1991.

[2] This tweetstorm argues that the Crowther study gets the carbon cycle wrong: “Finally, the reader is left with the impression (final paragraph) that out of 300 Gt of anthropogenic C, 200 Gt can be removed by tree planting. Unfortunately, the carbon cycle doesn’t quite work this way…. When we emit 1 tonne of C, half of it is removed by the land and ocean sinks; the other half is accumulated in the atmosphere. Well, the same applies when you remove 1 tonne of C from the atmosphere, half tonne of C is released by the natural CO2 sinks. So, take half of 200 [205] GtC.” I’m putting this only in a note because I feel it’s one for the judges.

[3] Crowley, with “canopy cover,” neatly elides the distinction between forest and plantation.

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About Lambert Strether

Readers, I have had a correspondent characterize my views as realistic cynical. Let me briefly explain them. I believe in universal programs that provide concrete material benefits, especially to the working class. Medicare for All is the prime example, but tuition-free college and a Post Office Bank also fall under this heading. So do a Jobs Guarantee and a Debt Jubilee. Clearly, neither liberal Democrats nor conservative Republicans can deliver on such programs, because the two are different flavors of neoliberalism (“Because markets”). I don’t much care about the “ism” that delivers the benefits, although whichever one does have to put common humanity first, as opposed to markets. Could be a second FDR saving capitalism, democratic socialism leashing and collaring it, or communism razing it. I don’t much care, as long as the benefits are delivered. To me, the key issue — and this is why Medicare for All is always first with me — is the tens of thousands of excess “deaths from despair,” as described by the Case-Deaton study, and other recent studies. That enormous body count makes Medicare for All, at the very least, a moral and strategic imperative. And that level of suffering and organic damage makes the concerns of identity politics — even the worthy fight to help the refugees Bush, Obama, and Clinton’s wars created — bright shiny objects by comparison. Hence my frustration with the news flow — currently in my view the swirling intersection of two, separate Shock Doctrine campaigns, one by the Administration, and the other by out-of-power liberals and their allies in the State and in the press — a news flow that constantly forces me to focus on matters that I regard as of secondary importance to the excess deaths. What kind of political economy is it that halts or even reverses the increases in life expectancy that civilized societies have achieved? I am also very hopeful that the continuing destruction of both party establishments will open the space for voices supporting programs similar to those I have listed; let’s call such voices “the left.” Volatility creates opportunity, especially if the Democrat establishment, which puts markets first and opposes all such programs, isn’t allowed to get back into the saddle. Eyes on the prize! I love the tactical level, and secretly love even the horse race, since I’ve been blogging about it daily for fourteen years, but everything I write has this perspective at the back of it.


  1. Joe Well

    It is always exciting to see an original Lambert Strether post. I learned so much about the nuances in this issue from reading the above. If I understand correctly, the practical takeaway from this is that reforestation should be one significant but not most significant tool in the toolbox of carbon reduction, and we can greatly increase the usefulness of this tool by scientifically managing forests with a view toward strategically harvesting trees. But also, given the time scales involved, some radical reduction in fossil fuel use and other greenhouse gas emissions is still going to be required.

    I think all the issues come together in real life: we build densely at the center of metropolitan areas and in town centers, abandoning residential single-family sprawl, thus simultaneously freeing land for reforestation and vastly reducing humanity’s carbon footprint (and saving a ton of money and commuting stress). Younger North Americans are already trending toward this view of an ideal society. North America still has enormous cultural cache around the world, and what becomes cool in the US and Canada will inspire many other people. I think this is achievable if we educate and activate younger voters to out-vote their elders, but we’ll never get there with our current political configuration.

    1. Dan

      Joe, Theory is nice, but after you have planted at least one tree and seen it start to grow,
      you will feel really good.

      Proud to say, I have a couple hundred in the ground–Guerilla style.

      Search for “plant trees in milk cartons” for the ultimate in recycling,
      lack of plastic, using local seeds etc.

      1. Amfortas the hippie

        Yes! to guerilla gardening in all it’s forms.
        when hanging around the hospital last september and october(the smoking area is the sidewalk circumscribing the campus), i became a tree seed saving nut(ha!).
        the mountain laurel( seeds are just now starting to germinate(hard seed coat)…might have as many as an hundred of those at some point. I’m thinking all down both sides of our county road/driveway. purple flower clusters(look like wisteria blooms, sort of) smell strongly of grape bubblegum.
        i collected a lot of acorns, too…( and…although the majority of them turned out to have small holes in them(sigh…should have carried my glasses with me on these rambles). ended up planting around 30 of these, each…with 30% germination so far.
        all this is in salvaged/saved black pots, filled with a mixture of city mulch,a little horse manure and my native sandy loam…stuck in the partial shade on pallets here and there out of the way. they get well water when i run the big overhead sprinklers(used to cool the garden july through september), otherwise rain only.
        the sycamores I attempted to collect, freeze and plant didn’t make at all.
        I’ve had better luck raking up a pile of leaves and acorns from under of of my big post oaks( and just transporting the whole pile somewhere else and sticking a surveyor’s flag in it(so i don’t inadvertently mow or drive on it)
        I’ll happily give any trees that make it away if i run out of room.

        it occurs to me….thinking about the property tax ag exemption silliness(cows, not chickens…wheat, not orchards, etc) in Texas, that reforestation could be encouraged that way….but the neoliberal capture and enclosures mentioned in the text should be considered and avoided if possible.

    2. Summer

      You think corporations are capable of building an ideal society?
      What’s the “ideal”?

      1. Joe Well

        >>>You think corporations are capable of building an ideal society?

        Where did you get that from???

        1. Summer

          “I think all the issues come together in real life: we build densely at the center of metropolitan areas and in town centers, abandoning residential single-family sprawl, thus simultaneously freeing land for reforestation and vastly reducing humanity’s carbon footprint (and saving a ton of money and commuting stress). Younger North Americans are already trending toward this view of an ideal society.”

          The younger Americans are being attracted to the densely populated areas for jobs. They have a lot riding on the belief in the corporation as benefactor.

          1. Joe Well

            >>The younger Americans are being attracted to the densely populated areas for jobs. They have a lot riding on the belief in the corporation as benefactor.

            That is such a dramatic, sweeping, out-of-left-field statement that I am really just astounded. If you have any links to illuminate your point of view, I would appreciate it.

            Every survey I have ever seen shows that for the US, the younger you are, the more critical you are of capitalism.

            Some results of a quick Google:

            Young people embracing socialism

            Young People’s Love of Cities Isn’t a Passing Fad

            The challenge for the North American Left and the planet is clear: vastly increase political participation by younger people.

            1. jrs

              City living itself tends to drive people leftward in beliefs. So it makes lots of sense they would be increasing at the same time. Of course there are 100 other variables.

    3. Kurtismayfield

      Once I see all of the following volunteered for reforestation, I will gladly volunteer my suburban environment:

      Every acre of Long Island east of Riverhead.
      Every acre of Cape Cod
      Nantucket, Block Island, and Martha’s Vineyard.
      All of Coastal Maine.
      Every Ski resort in the Continental US.

      Start with those and we can consider retracting suburbia.

      1. drumlin woodchuckles

        Those individuals who wish to leave suburbia for Big Cityville are free to do so. If the forces of Urban Chauvinism try to abolish and de-populate suburbia en masse, they will be opposed and resisted.

        Some suburbia may indeed get abandoned. Other suburbia will evolve into high-density semi-peasant settlements. Suburbia will have enough people on hand, living right there as they do, to be able to grow lots of food very intensively. That will not be possible in Big Cityville.

        1. Andy Raushner

          Suburbia is a debt based ponzi scheme. Much like all of capitalism. It rejects self efficiency in favor nihilism.

          1. drumlin woodchuckles

            We shall see who runs out of food and water first: the non-abandoned parts of Suburbistan . . . or the core-centers of Big Cityville. We shall see where the Great Ponzi built the highest Towers of Nihilism.

    1. Lambert Strether Post author

      That is a very good question, and I would say it’s a parallel issue, having read about Amazonia in 1491. That said, it’s really hard for me to see private equity-owned tree plantations using biochar at all, or not screwing it up if they try it (like Casella getting heavy metals and pharmaceuticals into the “organic” mulch it was producing from waste treatment plants).

      1. Samuel Conner

        I’m tempted to suspect that if the jackpot does not turn out that well for the survivors, we might see a return to wood-gas as a low-tech renewable carbon fuel. Biochar being a “waste product” of wood-gas generation, it might be a low-tech twofer. I was surprised to notice a few years ago that there is something of an online community of wood-gas enthusiasts.

        1. drumlin woodchuckles

          Since the Jackpot is designed to exterminate most people while making it look like an accident, anyone who even survives at all has come out very well. Because unless you are a member of the OverClass or one of their valued minions or treasured pets, you are not intended to survive at all. You are intended to die.

          So any non-OverClass non-minion non-pet persons who are still surviving after the Operation Jackpot has been completed have come out quite well on that brute survival level.

  2. Adam Eran

    I’ll go along with natural carbon sequester however it’s done. Michael Pollan reports that current, industrial agri-business burns 10 calories of petroleum to produce one calorie of food. Obviously we can practice agriculture differently (see permaculture, or Mark Shepard’s Restoration Agriculture for a little inspiration along those lines).

    Meanwhile, J.D. Alt has a very nice thought about how MMT could help here.

    1. drumlin woodchuckles

      More than just inspiration. Mark Shepard is refining and systematizing a whole system of how-to-do-its that reasonably literate and intelligent people can apply right where they live.

      And so is Gabe Brown. And so is Gary Zimmer. And so is Vandana Shiva in North India. And so are some others ( currently so few that we could learn all their names in a few days time.) Like . . .
      Eric Toensmeier . . .

      Albert Bates . . .

      and others which other people will hopefully mention.

    1. Steve H.

      Based on the video, without looking at the underlying papers, it looks like solid work.

      Add this to the RUFKM list: use of fossil fuels has allowed nearly a century and a half of reforestation, which has decreased desertification on a global scale.

      The 12’K estimate approaches an extraordinary claim, but if the scale is correct, she is describing a critical function. And she destroys plantation farming as mitigation in several ways.

  3. PlutoniumKun

    The study is obviously a ‘broad brush’ one. In reality, there are enormous levels of complexity in tree planting. In some circumstances tree planting may actually exacerbate short term climate change (for example, desert greening, due to changes in albedo). Much also depends on soil type – marginal lands in northern climes are often peat based, and its not clear that the drainage and release of methane would not be worse than maintaining these lands as pasture. As others will no doubt note, in many bioclimes, cropped grasses may well be a better bet for absorbing CO2.

    There is one line of thought, btw, that the Little Ice Age may well have been the result of reforestation of North America as native Americans were wiped out by disease. I’m not sure if this is still accepted.

    Simply passively growing trees is not nearly enough. In many circumstances, the trees would have to be managed to ensure the maximum CO2 absorption – in some places, plantation is better than wild forest, as the cropping ensures more use of CO2- sometimes mature forests are neutral or even generate more CO2.

    Planting trees can also be more complicated than people assume. My first job involved managing urban forestry establishment on waste land. Many expensive woodland simply couldn’t establish themselves on soils irretrievably damaged through tipping and the spread of spoil. I well remember the sight of a 15 hectare ‘forest’ reduced to dust after an unexpectedly dry first summer.

    I’m not sure the issue of existing land use and ownership is as complicated as may seem at first glance. People look at a lansdscape and think ‘oh, thats so beautiful, nobody should touch it’. But in reality, most landscapes, including many supposedly ‘natural’ ones such as the Scottish Highlands or Central American rainforests are far less natural than assumed. The former were forest up to 200 years ago, the latter (we now know), were often intensively farmed before Europeans came. Even the Amazon we now know may well have been as intensively farmed as much of the US in pre-Colombian times.

    1. Joe Well

      >>There is one line of thought, btw, that the Little Ice Age may well have been the result of reforestation of North America as native Americans were wiped out by disease. I’m not sure if this is still accepted.

      I’m a history nut and I’d never heard that before. If you have any names of historians, publications, theories, whatever, I really would like to dig more into this for my own curiosity. I don’t know how this could be proven. IIRC, there was a noticeable dip in atmospheric carbon in the 16th century, but how to definitively connect it to Little Ice Age?

      >>Even the Amazon we now know may well have been as intensively farmed as much of the US in pre-Colombian times

      But obviously they weren’t clear-cutting vast swaths or there wouldn’t be the biodiversity there is today.

    2. deplorado

      Also, Im pretty sure (I dont have a reference now) that the ocean does quite a bit more photosynthesis than dry land forests. Why don’t we focus on making sure the ocean can absorb more CO2 by supporting the plankton? Have the really smart eggheads thought about that? Much less real estate issues to work out I would think.

      1. PlutoniumKun

        There have been a variety of attempts to measure this – originally they looked at putting iron filings into the sea but it seems small scale attempts didn’t work. Other studies have looked at introducing key nutrients into areas with strong currents – its been done off western Canada. However, its not clear whether its a good idea and there are all sorts of international legal issues as it will only work in deep international waters.

        1. Antony Vo

          That is usually from fertilizer runoff. Pollution and hypothesis of the anthropogenic climate change from GHs are often conflated issues.

    3. Michael

      Thanks PK. The article at the link below reinforces your point that tree planting involves complicated choices, and the results can backfire or fizzle if the wrong choices are made.

      In California a lot of trees have died in recent decades due to fires and drought, which appear to be on the rise due to global warming. Here is an article from the U.C. Davis Arboretum website about the university’s planning for the climate of tomorrow:

      This part caught my eye:
      “What the future will look like at the local level has become easier to see, thanks to the web-based Climate Adaptation planning toolkits provided by State of California’s scientific and research staff (, along with even more localized climate studies done by Jim Thorne at UC Davis. This research suggests that in 2100, the climate of UC Davis may most closely resemble the current climate of Barstow, California in the western Mohave Desert (McBride & Laćan, 201).”

      Davis currently averages about 20″ of rain per year. Barstow gets about 5″. Reforestation plans for any given area will have to take into account the climate change that is already underway and baked in.

    4. Lambert Strether Post author

      > My first job involved managing urban forestry establishment on waste land

      Truly, the NC commentariat is the best commentariat

      > most landscapes, including many supposedly ‘natural’ ones such as the Scottish Highlands or Central American rainforests are far less natural than assumed.

      I probably didn’t write clearly. My concern is property ownership. Title issues are ubiquitous in Southeast Asia, for example, and I would bet elsewhere.

      1. PlutoniumKun

        Yes, sorry, you are right that ownership is a key issue, especially when there isn’t clear title – what I was trying to say is that as these situations are often far more dynamic than assumed (i.e. the vegetation and land uses change quite rapidly), its not necessarily a case of ‘imposing’ forestry on unwilling locals, more a case of adopting the right incentives, or preventing negative disincentives to achieve those aims.

        To give an example, a lot of commonage in northern hemispheres was originally peat – excessive extraction turned them into heath, which is what most people assume ‘commonage’ to be. Most of that will return to scrub and woodland if the current incentives for overgrazing is removed.

        1. drumlin woodchuckles

          What was it that allowed most of this traditional commonage land to begin life covered with peat . . . enough peat to extract and then over-extract? Was it naturally wet and boggy? If so, how did it become not wet and boggy anymore?

  4. clarky90

    Gardeners know that plants LOVE CO2 and warmth (the greenhouse)- so, Finally, a viable proposal. As warmth and CO2 increase, trees will increasingly flourish. Life has always worked this way.

    New Zealand’s One Billion Trees Programme

    “The NZ Government has set a goal to plant one billion trees by 2028. The One Billion Trees Programme will deliver improved social, environmental, and economic outcomes for New Zealand.

    Led by Te Uru Rākau (Forestry New Zealand) and funded by the Provincial Growth Fund, the Programme will:

    create employment and workforce development
    optimise land use
    mitigate climate change
    support Māori values and aspirations
    protect the environment
    support New Zealand’s transition to a low emissions economy.

    The Government has allocated $120 million through the One Billion Trees Fund for direct grants to landowners – particularly farmers – to include trees on their farms. The Fund does not support whole farm conversions and has a target of planting two-thirds NZ native trees….”

    Personally, I am most troubled by the pharmaceuticals, micro-plastics, herbicides (Roundup), pesticides, mutagenic chemicals, hormone disruptors……in the environment, Not by CO2, which is an organic plant food that has been around for billions of years.

    “By volume, dry air contains 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other gases.”

  5. Anon

    I’ll be one of the judges: The carbon cycle involves more than just CO2, there are other forms of carbon but it is CO2 that is most important because of it’s greenhouse effect. Trees absorb atmospheric CO2 during photosynthesis and transforms it into organic carbon and eventually the woody material of the tree. That woody carbon can be sequestered from the atmosphere for decades; until, of course, it is burned for heat/cooking and that CO2 is returned to the atmosphere.

    Original natural forests removed massive amounts of CO2 from the atmosphere. With urbanization we lose forests and radically increase atmospheric CO2 with fossil fuel consumption. Many scientists think our current fossil fuel CO2 production is 2 to 4 times greater than the current capability of ALL green vegetation AND the oceans (a natural CO2 sink) to absorb it. (CO2 absorbtion as carbonic acid upsets the ocean ecosystems (coral bleaching, etc.))

    While increasing global forestation is a step in the right direction to reducing atmospheric CO2, the ocean ecosystems may never recover to the condition they were in pre-industrialization. Yes, plant that indigenous tree (indigenous to a warmer climate?), but do the oceans a favor and drive your car less.

    1. wilroncanada

      Thank you anon. What is getting discussed are mitigations, NOT solutions. There are just three solutions: reduce, reduce, reduce.

      1. drumlin woodchuckles

        Well . . . if we reduced carbon gas output enough that plant-driven carbon-gas recapture could outrun the rate of continuing carbon gas output, then phyto-capture/ phyto-pedo sequestration could be part of a genuine global de-warming carbon-cycle rebalancing.

  6. Ray Phenicie

    Thank you sir for providing this information; many tree enthusiasts are overly optimistic on this fascinating topic.
    I love trees: I got angry when one of my commercial neighbors felled about 20 large, aged trees surrounding their campus. Here’s the gist of the complexity on measuring:

    The science involved in measuring co2 uptake is still developing; measurements are coming up with varying results as the exact nature of photosynthesis is still being worked out. This article reviews some of those difficulties. Hopefully your next dive into this topic will be able to include this perspective.

    Many scientists applaud the push for expanding forests, but some urge caution. They argue that forests have many more-complex and uncertain climate impacts than policymakers, environmentalists and even some scientists acknowledge. Although trees cool the globe by taking up carbon through photosynthesis, they also emit a complex potpourri of chemicals, some of which warm the planet. The dark leaves of trees can also raise temperatures by absorbing sunlight. Several analyses in the past few years suggest that these warming effects from forests could partially or fully offset their cooling ability.

    1. Synoia

      Exactly correct. The UK forestry commission planted conifer forests. They were silent and devoid of life.

  7. Divadab

    The carbon in trees harvested for lumber or paper is still sequestered- it’s not automatically released to the atmosphere as the paper seems to assert.

    I heat with wood – using dead or inferior trees culled from my woodlot. I also plant over 1000 trees per yr and transplant 2-300 from under power lines to where they will survive. The net effect is carbon negative imho since making space for better trees allows them to grow faster – the same amount of co2 pet acre is sequestered with fewer better trees.

    So a managed woodlot is part of a permaculture solution- providing fuel, lumber, and cash!

    Although I have a bunch of white pines now about 100 years old that I’ll never cut – nor will my heirs if they follow my instructions- the best among them are 4-5 ft in diameter and 100 ft high I really want to see where they will go in my remaining 30 years (if I’m lucky) – this is not justifiable based on pure co2 considerations since younger trees are more efficient at co2 sequestration and a 50-75 yr old tree is about optimal for harvest.

    Anyway the important thing is to vibrate positively with your land – love it and feel it and infuse yourself with the living spirits of the land, make the whole thing better with love.

    And thx Lambert for providing a venue and a space for neo-Druidism ideas- remember the sacred, take the time to give thanks for our Beautiful living planet, the spiritual space is so critical and so ignored in our materialistic culture that even the concept of revealed truth is banished when it is the source of all knowledge.

    God sends messengers- and they’re not bearded men in shimmering robes hovering above the earth- they’re more likely a bird, or a plant, or even a fungus. Take the time to know tree time and be a better human.

  8. Synoia

    What kind of trees? Deciduous or Coniferous? Coniferous forest are dead.

    How does on get the land?

    Area = 3 UK, or 2 France.

    Alternative suggestion: Build a pipeline 3m in diameter from the Mouth of the Amazon to Dakar in West Africa. Irrigate the Sahara. It’s only 2,500 miles.

    Then build another dozen pipelines.

      1. Tyronius

        Great articles! Thanks for sharing. Greening the Sahara is an idea thousands of years old- and yet timely. As a bonus, it dwarfs the area of India. Imagine what it could look like if it could be the African equivalent of the Amazon. Imagine what it could support in terms of people and resources. I don’t think that forest vs plantation need be a hard divide.

        As for the long term management of forest resources, I suggest we ask the Japanese; the Shoguns recognized the need to preserve forests to build their castles with and implemented a scheme where locals managed the forests for their own long term benefit. I suspect remnants of that system might still be in place.

    1. Math is Your Friend

      What kind of trees? Deciduous or Coniferous? Coniferous forest are dead.

      How does on get the land?

      Area = 3 UK, or 2 France.

      Alternative suggestion: Build a pipeline 3m in diameter from the Mouth of the Amazon to Dakar in West Africa. Irrigate the Sahara. It’s only 2,500 miles.

      Then build another dozen pipelines.


      I am pretty sure these cannot work. Various points:

      1. Coniferous forests are not ‘dead’ Some of the larger and more interesting animals in the world live in them (bear, wolves, moose, elk. lynx). along with a sufficient density of prey animals to keep the carnivores and omnivores happy. If you’ve looked at ecology, you know it takes a lot of prey to support one apex predator. If interested look up “Why Big Fierce Animals Are Rare: An Ecologist’s Perspective” by Colinvaux.

      2. The scale involved in this would by past gigantic. France is fairly small, only about 640,000 km^2. The areas cited in the OP were about the same as the US, China, or Canada, all or which are about 15 times the size of France. (just a bit under 10,000,000 km^2 each).

      3. A 3m pipe cannot move a geologically/geographically large amount of water any distance let alone 4,000 kilometers. Distance makes a huge difference. We’ll get to that in a moment.

      To pass a relatively small river (Welland River, drains about 900 km^2) under a 100m wide canal (Welland Canal) requires six parallel 6.5m inverted siphons. This only works because the force of the water flowing from the upstream side pushes the water through the siphon – there is an overall gradient to the river which is why it is a river, and not a long pond.

      The longer you make the siphons, the more friction, turbulence, etc. sap the energy of the moving water. make it long enough and the water stops moving.

      But…. the ocean is flat, gravitationally. the west side of the Atlantic is not higher than the east side. If your want water to move, you have to push it. Pumping stations on the bottom of the ocean.

      4. Underwater construction is a big deal. It is hard, expensive, and largely avoided. When laying things like cables, that’s what they do. The don’t build them on the bottom, they just unspool them from specialized (interesting looking!) ships and hope they don’t have to fish them up for a repair. And cables are tiny compared to even one or two big pipes… where you would probably need hundreds or more.

      5. The Sahara is mostly rock, and the rest is mainly sand. Very few plants do well on a diet of sand and water. They like organics in the soil….

      6. I shudder to think of the ecological disruption if this could be done – the entire ecology of Northern Africa would probably be fubared, and I wouldn’t be at all surprised if the weather patterns changed over a huge area.

      7. The disruptions to ecologies deprived of the fresh water from the Amazon, the changes in oceanic temperatures, currents, densities and nutrients could have terrifyingly wide spread effects.

      There may be ways to engineer a biological carbon capture, but this one looks like way too much work for entirely too unpredictable results.

    2. PlutoniumKun

      Unfortunately, studies I’ve seen indicate that reforesting the Sahara would be neutral at best with regards to climate change. This is due to albedo effects and cloud formation. But if you did want to do it, you would not pump water from the north – it would be far more efficient to use fossil groundwater (there is lots of it under the Sahara) and solar powered desalination.

      In reality, it would make far more sense to focus reforestation on deforested areas, not desert.

      1. Synoia

        In the 16 Century it is reported that one could cross the Sahara in a day on a horse. Much of the Sahara is a deforested area.

        Deforested by Goats.

        The Romans collected Lions from N Africa for their Arenas. Those Lion had to be hunting herbivores, and the herbivores had to be eating something more that there is available now.

        Reversing the effects of the Punic Wars would be interesting.

        1. Math is Your Friend

          “In the 16 Century it is reported that one could cross the Sahara in a day on a horse. Much of the Sahara is a deforested area.”

          But is that soil still there?

          If not the project is orders of magnitude more difficult and complicated.

      2. Synoia

        Tropica forests peak temperature is about 95 deg F. Humidity nearly 100%

        Desert peak temperatures are 120 to 140 deg F.

        Trees adsorb “energy” or “heat” to make their sugars. Trees are much more complex than simple Carbon Dioxide consumers. Do you have a reference to albedo reflection vs Tropic tree adsorption?

        Deserts generally don’t have clouds. Tropical forests do.

        I’ve lived in both. Despite the insects I’d take the forest first every time.

  9. JohnM

    can’t see the soil for the trees….

    the rule of thumb is that tropical regions store carbon above ground (ie, in the trees) since constant warm temperatures result in mineral rich/organic matter poor soils, while temperate regions store it in the soil as root shedding and plant exudates feed a soil ecosystem which accumulate as seasonal cold temperatures stop natural decomposing. so while planting trees in tropical areas makes sense, grassland may make more sense in other parts of the world. even these people think so.

      1. Synoia

        Better to plant them in the prairies as added fertilizer. Their remains would add to soil enrichment.

        I notice Boeing is taking an active interest in such a program. /s

  10. The Rev Kev

    About a week or so ago there was an article in Links on how billionaires were buying up vast tracks of the United States. After reading this, the thought occurred to me that perhaps one of the main reasons that they doing is so that they are in position to benefit from any large-scale tree planting programs by having ownership of the land to do so. Can’t plant trees if you don’t have the land to do it on.

    1. JBird4049

      If things get bad enough, land will simply be seized by the government using eminent domain. A supposedly “fair” compensation will be given so the suckers may be those billionaires.

  11. Brian Westva

    I haven’t read the study so l can’t comment on its validity. I am sure that there are limitations or shortcomings as there are with every study. However it did make it through the peer review process for what it’s worth. I think it is very important that tree planting and forestry become part of the solution to climate change. Restoring natural forests and avoiding plantations is the best way to proceed. Natural forests are going to provide numerous co-benefits that plantations and other technologies won’t provide such as raw materials, habitat, evaporative cooling, high quality water, recreation, and many more. I think that there is plenty of land. Landowners need to receive payment or cost share for restoring forest and then be paid for maintaining the forest for carbon sequestration. This could be a combination of existing federal and state programs along with new or existing carbon offset markets.

    I am tired of hearing about the latest and greatest CO2 sucking machine that runs on electricity. It just does not make since when you have forests and trees that already do that. We don’t need to spend 2 more decades with R&D for some new machine. We need large scale tree planting all across the global. And of course renewable energy.

    1. Lambert Strether Post author

      > Restoring natural forests and avoiding plantations is the best way to proceed.

      That’s how I feel (and a feeling is all it is; but you can’t watch a garden for any length of time and come away thinking that plants are stupid…).

      I couldn’t work this in, but it occurred to me that the flip side of “forest = plantation” is using the plantations to feed BECCS. Again, pure feeling, but I feel a lot of the technocratic solutions come from the mindset that “We did nothing wrong, we just have to reboot the system with different inputs.” So, let’s double down and let — speculating freely, here — private equity reforest the world with plantations (and the help of the occasional U.S. gunboat).

      1. JBird4049

        So, let’s double down and let — speculating freely, here — private equity reforest the world with plantations (and the help of the occasional U.S. gunboat).

        Is any speculation really needed? The link to the Sitka plantations in Ireland said that the trees were used because they were fast growing and the companies that used them made a nice profit.

        There are almost thirty native Irish species and somehow they could not be used is a wonder indeed.

        It is like when the San Francisco Bay Area was suffering from the massive deforestation of the 19th century and the answer was to plant God’s favorite torch, the Australian Eucalyptus, in a region that not only naturally has 2-3 fires every decade everywhere with regular droughts, but that the local ecology requires it. That is why Redwoods have bark that turn ablative (heat reflective) when burnt or that drought tolerant oaks are common outside redwood forests. That and the fact that the clay soil around here does not stop them.

        Of course, a fully functioning redwood (and it’s not devoid of life) or oak forest takes human lifetimes to fully develop. Much longer than the Australian weed tree.

  12. TG

    Before WWII, the Japanese government’s policy of creating a population explosion crushed the average Japanese into dire poverty. After WWII, the fertility rate plummeted, and the Japanese slowly became rich. By many objective metrics (like life expectancy), they are now the most prosperous major society in all of human history.

    But.. the low fertility rate means that factories are being abandoned and going back to forest, old roads are decaying and going green – perhaps, in a few centuries, if current trends continue, Japan may have a population density only five times that of the United States. The horror! We can’t allow that! There must be more growth, and more people, and more consumption! If the Japanese people selfishly won’t breed like rodents, they must be flooded with the surplus population of the third world!

    Not that long ago, Canada had a roughly stable population of about 25 million. Their per-capita energy consumption was very high, quite a bit higher than the United States, but with a moderate population, and abundant land, Canada was an example of man in harmony with nature. We can’t have that. So the elites have decided that Canada’s population simply must be increased to 100 million and beyond. Because we can’t have unused land! We can’t have unused potential! We must strip mine every asset in the name of cheap labor and growth for the sake of growth! And everyone who says different is a racist and a fascist and literally Hitler.

  13. Ian Perkins

    In my opinion, reforestation such as the paper recommends would probably capture a lot of carbon, and we absolutely should be attempting it. (Not in the Sahara, to be sure, but the paper in no way suggests that – “More than 50% of the tree restoration potential can be found in only six countries: Russia, United States, Canada, Australia, Brazil, and China.”) However, it will only be of any use in the long run if the trees are still there in 50 – 100 years. That’s a long time in which all manner of political, economic and environmental disruption can occur, and the trees disappear.
    Secondly, many of the comments seem to focus on the type of reforestation – forests or plantations, evergreen or deciduous, etc. As I understand it, the paper looked at the types of forest that would naturally grow in different areas: “our maps reveal that there is likely to be space for at least an additional 0.9 billion ha of canopy cover. If these restored woodlands and forests were allowed to mature to a similar state of existing ecosystems in protected areas, they could store 205 GtC,” and “The focus on protected areas is intended to approximate natural tree cover.”

  14. Susan the other`

    I agree this is an ownership argument. Plantations are not a good idea regardless of ownership because they preclude diversity. Without diversity we resort to toxic tricks to keep the enterprise going. Etc. But that is not to say that the billionaires can’t comply. They can. They’ll have to adjust their idea of “profit” but they can do it. A fund established to reforest the planet using all the science we have is feasible. The fact that trees grow slowly and need nurturing should not be a problem. Nor should cutting back old forests and diseased ones like the devastated pine forests currently losing the battle with the bark beetle. In Germany they are replacing vulnerable forests with new varieties of trees for better survival. I keep remembering the Link (Lambert) about a year ago about the Manti-LaSalle most-ancient grove of aspens. My all-time favorite place to just stand and breathe. To my regret it is suffering some demise – and it is probably due to old age and lack of diversity. Just a guess. But it could also be because the atmosphere has changed and gradually it is even putting trees at risk. Up there (Fish Lake, Utah) it is 10,000 ft. in altitude and if the atmosphere is “thinning” those trees would feel it first. I hope that is not the case. So diversity, as opposed to plantation nonsense, is important. We have all the evidence we need to start a project. And we could always use a few enlightened billionaires. It could be a good thing.

    1. Susan the other`

      Speaking of getting out into the forest, I hope Wukchumni is doing OK. No word on the California quakes.

      1. Synoia

        California Quakes

        Many reports of property damage. No reports of injuries or deaths.

  15. Ian Perkins

    Various articles about this paper have mentioned a tool on the Crowther Lab website which “enables users to look at any point on the globe, and identify the areas for restoration and learn which native tree species exist there.” Has anyone managed to locate this tool?

  16. Jeremy Grimm

    Appropriating land for reforestation would be a problem in efforts to reach the scale of reforestation needed for the level of carbon sequestration desired — a level sufficient to augment the “CO2 budget’. But long before broaching that concern we might start by doing a better job of ‘managing’ the existing public lands.

    I share The Rev Kev’s concern [July 7, 2019 at 8:23 pm] that reforestation, indeed any of the plans for carbon sequestration offer prime opportunities for Neoliberal exploitation. And consider that any actual or imputed carbon sequestration will serve as means to increase the CO2 budget” making room for “safely” burning more fossil fuel. Reforestation does have the major merit of offering a club of sorts for quashing other less benign methods for geoengineering like dumping iron filings in the oceans, or spraying SO2 into the atmosphere, or space mirrors. Besides, I like trees.

    The question whether it were better to reforest naturally or by plantation hinges on how the vague notions of “natural” and “plantation” are defined. They start on very unequal pejorative footing. I’m not sure either will be as effective as might be hoped. We know far too little about how the climate will transition to its new state. I very much doubt the transition will be as smooth and monotonic as it is portrayed. Whether planting naturally or “plantationally” however either may be defined won’t matter much. And why stick to trees? I like bamboo too.

    I believe cut-and-try GSM methods will be necessary in tailoring plants and in the selection of plants — trees, grasses, bushes, even fungi and algae — to maintain a continuity of plant life in the greatest diversity we can. I believe the changes in climate will be too rapid for evolution to deal with in a timeframe meaningful to any efforts to maintain the continuity of some representatives of Humankind. How viable are Asimov’s yeast vats or the algae vats in other science fiction? If we must live below the surface we will need to learn a lot more about getting along with and cultivating fungi.

  17. Winston Smith

    An anecdote on tree planting and our inability to look long term: when I was about 13yrs old my father enrolled us into a tree planting effort on land we owned targeting an open field down a gentle mountain slope that was a favorite path for snowmobiles to pollute our winter days. The idea was that eventually the trees would grow and no more snowmobiles. nearly 30 yrs later, a tall forest of sturdy pines is on show and I feel a surge of pride in having partaken in that effort…

    1. Wukchumni

      My dad planted around 25 Giant Sequoias @ our suburban abode in L.A. in the late 60’s, and 13 of them survive, thriving.

      In typical Sequoia fashion, a few of them are crooked, one tilting @ a 10% list towards the neighbor’s house, and said forest also wrecked a wall when the shallow root system spread as they are wont to do.

      They’re about 60 feet tall now, and until my mom sold her pad 4 years ago and I could always go home again, it was a favorite haunt of mine.

  18. Wukchumni

    Has there been a recent study done on the 3 billion trees planted by the CCC in the 30’s & 40’s?

  19. Roy G

    I just returned from a two week visit to China (Beijing, Xian, Chengdu and Shanghai), and I have to say that one of the most remarkable things I noticed was the great extent of planted trees and greenery in every available space. While the Chinese govt can be criticized for many things, they are certainly very forward in this area.

  20. McWatt

    My family owns a tree farm in the rural Midwest. It is not for the faint of heart. The reality is the costs are so
    great for maintenance and trimming for the health of the trees that you probably wont ever be able to get people interested in investing in tree plantations.

    However, the Midwest farmers have denuded the trees from their fields in a search for greater crop yields. If we could create a program of planting wind breaks and river banks as Roosevelt did in the 1930’s it would go a long way to help.

  21. Bernalkid

    Planted a sequoia in SF and thrived, shaded the back yard, visible from satellite photos. OTOH Monterey pine succumbed to pitch canker, sycamore has problems with anthracnose natives do great though. Lots of shade from buildings.

  22. drumlin woodchuckles

    A retired engineer named John Hamaker had a very idiosyncratic theory of Ice Ages and Ice Retreats.
    His theory was that the available mineral nutrients for plant growth slowly leached, eroded and attrited away over millions of square miles of plant-growing land. After plant-growth was reduced enough by disappearing plant-support minerals, aerial CO2 would build up to the point of warming the global, evaporating vast amounts of water from the tropic seas, moving it to the high lattitudes and dumping it as snow so fast that it built up into ice sheets. In other words, soil-nutrient depletion raised the skycarbon which warmed the global which moved so much water to the poles and near-poles so as to set off an Ice Age.

    Over time the grinding ice would liberate so much new plant-support minerals in glacial till moving downwind and downstream from the ice front that new waves of plant growth could arise on the re-mineralized ice-free areas and suck down the excess skycarbon and de-warm the global and hence reduce the vast ice-building volumes of water vapor leaving the tropics and stopping at the poles.

    It is a highly , umm . . . “unique” theory, to be sure. But one interesting side effect of the theory is the suggestion that multi-source rock be ground up powder-fine and fed to the plants growing on some soil and fed to the soil on which some plants grow. The growth of those plants was increased exactly as predicted.

    The theory gained attention, became a fad in some circles and then faded away. Only some books, adherents and ghostly digital footprints remain.
    the whole book can be read at this link.

    It lead to a “movement” called Remineralize The Earth . . . which also leads a ghostly existence on line.
    For a while “glacial rock dust” was sold in bags by many outlets. I bought such a bag myself once and I have my memories of 2-foot-tall dandelions and other noteworthy achievements from using the “glacial rock dust”. But that too fade mostly away. Some companies still sell versions of this product-concept.

    The question arises: what if multi-source-input rock and mineral materials could be ground up into flour fine dust and applied by low-flying aircraft to forests already existing? Would that mineral input speed the growth and hence the skycarbon-suckdown of all those trees and plants? John Hamaker felt sure that it would. How much carbon would be released burning the fuel to grind and apply all that rock dust? Would the forests it was applied to suck down more carbon than the carbon that was released getting and applying the rock dust? If so, and especially if so by a large enough margin to make a practical difference; then it would be worth the carbon skyloading to mineral dust-feed several million square miles of current forest in order to suck down way more carbon than was skydumped to start the process.

    There has long been a “natural experiment” under way which supports this concept. Years ago I read that a little bunch of mountains in Chad form a natural “wind channel” through which the wild winds blowing grind up desert dust superfine and lift it high enough to blow over to Brazil before falling out to feed-mineralize-nutritionize the Amazon Rain Forest. I have found here an article which talks “around” this fact if not directly about this fact. It does discuss the larger concept.

    At the time I read about this, I thought: why not build a railroad from the nearest serious African coastal port city all the way to the upwind head of this valley. Why not ship into this area nutritionally-balanced mixes of Rain Forest Nutritional-support Optimized rock and mineral flour mixed with seaweed flower and maybe even fish-meal flower, release it into the Chad Wind Tunnel for blowing over to Brazil, and super up-feed the growth of the Amazon Rain Forest? Thereby super up-raising the rate of skycarbon suckdown by the Amazon?

    Of course the Bolsonarists in Brazil may make that idea moot by carefully turning the whole Amazon into a soybean desert. But that is a newly emergent threat.

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