On forests’ role in climate, New York Times op-ed gets it wrong

"Wrong at so many levels that it is hard to cover them all here..."
A scientist believes the New York Times op-ed was ‘wrong at so many levels that it is hard to cover them all’.

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Last week, Nadine Unger, an assistant professor at Yale University, published an opinion piece in The New York Times stating that the way to save the planet was to not plant trees. This opinion was wrong at so many levels that it is hard to cover them all here. There are many reasons why we need to protect forests and to plant trees—protecting water supplies, reversing the loss of biodiversity, ensuring that we have pollinators for crops, and sequestering carbon to reduce human-induced climate change.

The article opens with a discussion of the international REDD+ (Reducing Emissions from Deforestation and forest Degradation) mechanism, which aims to reduce tropical deforestation and enhance carbon removals from the atmosphere by re-growing tropical forests. Unger says it won’t work, pointing to an old argument about the offsetting effects of carbon release and the increase of energy reflection when forests are removed—the so-called albedo effect.

The argument recognized that forests are dark (look at an aerial photo or a Google Earth image) and absorb solar energy, while agricultural fields and pastures are lighter and reflect solar energy. It’s the reason why a black car sitting in the sun with the windows closed gets hotter than a white one. So: forests absorb energy and heat the lower atmosphere. A 2007 study led by G. Bala (and others) published in Proceedings of the National Academy of Sciences showed clearly that globally deforestation would lead to cooling. The albedo effect surpasses the carbon effect in the energy balance, and the Earth cools when forests are removed.

However, and this is an important “however” for this discussion, when the authors looked at how the carbon and albedo effects played out at different latitudes, they concluded that the albedo effect overwhelmed the carbon effect at high latitudes (northern temperate and boreal forests) and the carbon effect overwhelmed albedo at low latitudes (the tropics). Stopping tropical deforestation and increasing tree planting in REDD+ countries, where the albedo effect is smaller than the carbon effect, makes sense from an energy balance point of view. This is why the international effort focuses on stopping tropical deforestation and rehabilitating degraded tropical forests. There is no REDD+ mechanism proposed for northern countries.


Later in the article, Unger trots out Ronald Reagan’s absurd statements about trees polluting and the importance of volatile organic compounds (VOCs) in the formation of tropospheric ozone and methane. She notes that VOCs, natural components of the atmosphere, react with other anthropogenic pollutants (particularly nitrogen oxides) to form these greenhouse gases. One would think that if VOCs are natural components of the atmosphere, the blame lies more in the newly introduced pollutants.

Not according to Unger. Atmospheric chemistry is full of non-linear processes—scientists figured these things out decades ago. When nitrogen oxides (also natural constituents of the atmosphere) are present in low concentrations, the reactions with natural VOCs result in the destruction of ozone and methane, so naturally these VOCs help keep the atmosphere clean. However, when nitrogen oxides are present in high concentrations as a result of human-caused pollution, VOCs react with these pollutants to produce more ozone and methane.

One must question the motives of a scientist who grandstands on the eve of an important international conference that will give specialized attention to forests to cast doubt on the discussions

Louis Verchot

So the problem is not that forests pollute. The problem is the unintended compounding problems associated with human pollution. Indeed, research shows that rather than trying to control ozone pollution by reducing VOCs, it would be more cost-effective to reduce pollution from nitrogen oxides. Cutting down the trees is the wrong solution.

Unger also completely skips over the issue of black carbon. When forests are cut and burned to prepare the way for agriculture, the fires emit back carbon into the atmosphere. This black carbon absorbs heat, like the aforementioned black car. When the fires that burn are on peatlands, it creates enormous other problems, such as the haze events that plague Singapore and other Southeast Asian cities from time to time.

Finally, Unger goes off on a strange tangent about oxygen. No scientist has ever suggested that deforestation would be catastrophic or even a little problematic with respect to atmospheric oxygen. There is no issue here—it’s a red herring.

There are all sorts of good reasons to keep forests around; reducing climate change is just one of them. One must question the motives of a scientist who grandstands on the eve of an important international conference that will give specialized attention to forests to cast doubt on the discussions. One must also question the motivations of The New York Times for printing such a piece.

Editor’s Note: What do you think about the issues raised in this article? Join the discussion by writing your comments in the space below.

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16 responses to “On forests’ role in climate, New York Times op-ed gets it wrong”

  1. Yes, it was a strange place to put this sort of argument. One thing I notice is that they did not allow comments on the opinion piece. NYT should have done more research on this topic before publishing this piece…

  2. Tracy J says:

    Excellent piece, Lou, thanks for getting it out there so promptly. Especially for noting the policy stumble – not only are there scientific problems with her claims, she completely misunderstands or misrepresents what REDD is primarily about – protecting standing forests in the tropics. And yes, one must wonder about the timing of an article that seems to have been rushed out the door without sufficient review, just to take advantage of this important moment in the global climate policy process

  3. Robin Chazdon says:

    Big mistake for NYT and for Dr. Unger. Thank you Louis Verchot!

  4. Kevin Brown says:

    Thanks for this response, Mr Verchot.

    There was no mention of forests and adaptation. Forest provide numerous benefits for ecosystem services beyond carbon sequestration such as livelihoods, groundwater recharge, and attenuation of severe weather – services that keep nations resilient as climate changes. To use the idea that there might be some uncertainty about the net cooling effect of high-latitude afforestation as rational for scrapping REDD is irresponsible in the extreme. NYTimes, how did you let this happen? You can’t suffer a 20-minute phone call to check with others in the field?

  5. Avery Cohn says:

    Here’s a response I prepared critiquing Dr. Unger’s op-ed:
    The op-ed’s claim that limiting deforestation will make warming worse appears to be based on the author’s recent paper in Nature Climate Change – doi:10.1038/nclimate2347 . That paper has an odd disconnect between data and discussion. This disconnect is magnified in the op-ed. Bottom line– nothing in the paper supports the op-ed’s suggestion that limiting deforestation will make global warming worse.
    The paper reports results of model experiment comparing world with and without the deforestation that occurred from 1850 until the 2000’s. It finds that the reduction in forests (and their replacement with other natural vegetation) leads to a decline in volatile organic compounds. The average effect of this decline across the whole globe is -0.11+/- 0.17 watts/m^2 . The mean is negative, but the finding (by the author’s own “uncertainty range” reporting) is not significantly different from zero. By comparison, it appears from Figure 1 that the CO2 effect is roughly 0.3 +/- 0.2 w/m^2. This CO2 effect, by contrast, is significantly different from zero. In the paper, the two main findings are said to be that: (1) the net local effect of the volatiles lost when trees are cut is cooling, and (2) that this volatiles effect is of similar magnitude to albedo and CO2 effects from deforestation. I question finding (1) because the effect is not necessarily cooling (it’s not significantly different from zero forcing). Finding (2) is negated if we don’t confidently know the sign of finding (1). So what does the paper find? Primarily that VOCs have the potential to be a non-negligible component of net warming and cooling from deforestation (even excluding cloud interactions). This is important, but nowhere near as controversial and certainly not a rationale for the op-ed. Two final notes…. First, a global average metric for VOCs is problematic just like a global mean metric for surface albedo is problematic. We really need to be to be reporting the regional impacts of these non GHG climate forcings. Second, I’m not sure what the +/- range reported represents. It appears to correspond perfectly to the “barred black lines” described in the Figure 1 caption as the “uncertainty range.” Uncertainty range is often a synonym for 95% confidence interval. It’s not clear what the range represents. Perhaps uncertainty across multiple model runs using a range of different parameter values? But I didn’t see this described in the article.

  6. Sarah Workman says:

    Excellent response Dr. Verchot. Thank you for expression of rational arguments in the face of an untimely, sadly false and publicized, opinion.

  7. Debbie Lipscombe says:

    Weird. Can’t believe how many appear not to have read Unger’s paper, or have just misunderstood it completely. The point is, wasting energy on an issue that has minor effects on CC is a waste of time. If it’s a lifelong project then it’s FFs that need to be reduced because they are overwhelmingly the problem. A bit like whipper-snipping all around the edges of your back yard and wondering why6 the grass still looks long. At no time does she underestimate the benefits of ecosystems. Why would she. The topic was climate change.

    • Xiaoting Hou says:

      It is nothing weird. Unger’s Op-Ed was written in such a confusing way and she linked her arguments with policy decisions she clearly does not understand fully. The point she should really be making, and as you said, is that politician should take more affirmative and transformational actions towards climate change including revolutionize our energy system rather than just planting trees. Instead, the Op-Ed ended with a sweeping statement against increased international funding towards forestry while the existing funding is insignificant and far from enough to save the natural forests in tropics which the author should have argued to save based on her study. Here is an example of a more effectively way to make the same points without confusing and misguiding the public and policy makers:

  8. dougfir says:

    Thank you for helping to clarify Dr. Unger’s confusing op-ed in the New York Times. Nothing can change the fact that forests store carbon and logging emits carbon. Depending on how we manage them, forests can be part of the problem or part of the solution to global warming.

    More info: Heiken, D. Myths & Facts on Forest, Carbon and Global Warming slide show clarifying many misconceptions about forests, logging, and carbon:

  9. I think there are some fundamental myopic flaws in the
    assumptions of the author of the article. The author starts off by rightly saying that the system is complex, and understanding the complex interactions is important. That is correct. But only the complexities in support of her stance is elaborated and expanded. For the others the shortcut of non-elaboration and generalization is taken.

    For example:

    “So it’s understandable that we’d expect trees to save us from
    rising temperatures, but climate science tells a different story. Besides the amount of greenhouse gases in the air, another important switch on the planetary thermostat is how much of the sun’s energy is taken up by the earth’s surface, compared to how much is reflected back to space. The dark color of trees means that they absorb more of the sun’s energy and raise the planet’s
    surface temperature.”

    The assumption track is as follows:

    Incident Solar Radiation => on Black body => Black Body absorption => skip… skip… skip on intermediate complex processes=> Go direct to Therefore Surface of Earth heats up… skip… skip… skip… conveniently taken to justify stand against planting of trees??

    What can happen inside the multiple skipped steps?

    Yes trees absorb radiation as “Dark” bodies… but what happens
    to this energy? It doesn’t stay static and drive up the earths temperature. In the tropics it goes towards phase changing water, from water to vapor, usually evapo-transpiring from the tree’s leaves itself. The heat is consumed in phase changing water not stored to drive up temperatures. This is what accounts for the humid but cool context under a rainforest canopy. Any heat radiation penetrating the canopy and incident on the soil again goes towards phase changing water, water in the soil moisture, but this happens in a limited quantity based on saturation point of
    vapor in the surrounding. The rainforest ecology is directly linked to
    the water cycle, whether scientists understand the full process or not. So is any forestry ecology.

    A site that elaborates some of the possible interactions is my company’s own website:

    So the skipping of intermediate steps to jump to conclusions is not scientific and leads to incorrect assumptions.

    Don’t forget, it was the evolution of the total forestry based ecological system (based on everything from algae to hard wood trees) that slowly conditioned the earths ecology to its current state from a primordeal soup.

    “In order to grow food, humans have changed about 50 percent
    of the earth’s surface area from native forests and grasslands to crops, pasture and wood harvest. Unfortunately, there is no scientific consensus on whether this land use has caused overall global warming or cooling. Since we don’t know that, we can’t reliably predict whether large-scale forestation would help to control the earth’s rising temperatures.”

    Really? Over the span of geological time I thought that trees
    did really well in sequestering carbon, and converting it in to the various fossil fuels we know today, from coal to crude oil. Where ever we have large oil fields some form of forestry system got fossilized in to oil or coal. (This includes oceanic forests as well).

    It was pretty well sequestered until humans began to burn it
    to obtain energy.

    Remember this system worked really well over far larger time
    spans that our modern science has existed. Never mind contemporary scientists, the entirety of the existatant time frame of modern science is insufficient to measure “whether this land use has caused overall global warming or cooling.”

    But one thing is sure, it DID sequester carbon, it did enrich the atmosphere with oxygen.

    “Worse, trees emit reactive volatile gases that contribute to air pollution and are hazardous to human health. These emissions are crucial to trees — to protect themselves from environmental stresses like sweltering heat and bug infestations. In summer,
    the eastern United States is the world’s major hot spot for volatile organic compounds (V.O.C.s) from trees.”

    Of course trees do! Even we do, pardon the expression, fart. I.e. emit methane. But overall over time do trees draw down what they emitted, yes they do. It’s all part of the ecological equilibrium where
    some loops emit, but are drawn down in to overall carbon neutral loops, other loops like fossilization, though they also emit CO2E in the process, also do overwhelmingly sequester carbon. In fact the only known mechanism of converting CO2 in to complex forms of C happens inside a tree/plant. No industrial process can do this. Therefore my contention is that the articles negativity based on the emission of involving tree V.O.C.s is fundamentally myopic and flawed.

    “While trees provide carbon storage, forestry is not a permanent solution because trees and soil also “breathe” — that is, burn oxygen and release carbon dioxide back into the air. Eventually, all of the carbon finds its way back into the atmosphere when trees die or burn.”

    No they don’t! Some of the carbon from plant matter remains in the soil as inert carbon, especially over geological time. That is what produced the fossil fuels we burn today. But the nature of the carbon sink is not static. Don’t expect it to be, because by nature the whole system is highly dynamic. The true carbon sink is the live forestry stand stock over total emissions artificial and natural, together with sequestration functions like adding inert carbon to the soil.

    Albeit this happens on minuscule scales that require large areas of the planet to be forested to become effective. Remember when the system was progressive the whole planet (more or less) was pure forestry, with even humans just another species within it. Thus there exists an equilibrium or crossover point where there is a requisit bare minimum total forested area vs. biotic and natural abiotic emissions, above which the system is progressive in sequestration, at which the system is neutral. Today we are undoubtedly severely under this figure with the level and scale of deforestation our species have undertaken. Don’t blame the system for our self-centered shortsighted consumeristic trends. The system works, provided there is enough land under forestation. We need to figure out this quantity and relate it to our contemporary emissions levels, and bring the system back, first to progressiveness then to equilibrium.

    “Moreover, it is a myth that photosynthesis controls the amount of oxygen in the atmosphere. Even if all photosynthesis on the planet were shut down, the atmosphere’s oxygen content would change by less than 1 percent.”

    Again myopic. Who and what brought the atmospheric oxygen levels to its current state? Aliens splitting hydrogen and oxygen from water? Or was it photosynthesis by plants over geological time? Roughly our current oxygen ratio in the atmosphere is 20%. There have been instances when the planet was covered in Gigantic trees, unhindered by human consumption, the atmospheric oxygen was at the 30% mark.

    “The science says that spending precious dollars for climate change mitigation on forestry is high-risk: We don’t know that it would cool the planet, and we have good reason to fear it might have precisely the opposite effect. More funding for forestry might seem like a tempting easy win for the world leaders at the United Nations, but it’s a bad bet.”

    Yes, in the lackadaisical efforts we make today. But if the efforts were made at a rate or magnitude in keeping with the amount of land required to be reforested the system will work. However if we can find such amounts of land is truly the question. Therefore, we may have to use a hybrid of reforestation combined with cascading steps of industrial utilization to accelerate or maximize the carbon neutral and/or sequestering functions….

    For detailed elaborations refer

    When taking on the debate of “To Forest or Not to forest –
    that is the question?” one has to eventually answer the sub question, what price for reforestation….. That I think is the key question. All aversion to reforestation is because it is felt by
    those who have the money that reforestation is a mega cost, with no financial returns. This has to be the thought-line behind:

    “Closing paragraph end:
    … One must question the motives of a scientist who grandstands on the eve of an important international conference that will give specialized attention to forests to cast doubt on the discussions. One must also question the motivations of The New York Times for printing such a piece.”

    To set aside this setback, it is important to evolve mechanisms where reforestation can award an ROI (Return On Investment), albeit at patient capital Internal Rates of Return (IRRs). But if there is a financial kick back, it allows us to take decisive steps and to invest in it (not spend as a cost) and it can and will be at a magnitude needed. We can’t have millions of acres deforested, on a monthly/annual basis, and have only thousands of acres of reforestation, reforestation has to occur at a rate of 10s of millions of acres.

  10. chris bennett says:

    perhaps the new York Times op-ed and CIFOR response should be seen more as a wider symptom of global forestry rhetoric being overly-driven by (genuine) carbon-centric concerns that tend to drown out other major benefits of forests.

  11. erichj says:

    Biogenic-VOCs, given the new research on aerosol formation, are an environmental plus. My rebuttle to Unger & Ken Caldera I post bellow;

    My two cents for the trees;
    Dr. Unger “In reality,” is just as guilty about complexity as she accuses others of being.
    “the cycling of carbon, energy and water between the land and the atmosphere is much more complex.”
    Quite so!, has her group at the Yale School of Forestry and Environmental Studies, considered the paleoclimate data for afforestation?

    Anthropogenic activities led to the stabilization of atmospheric CO2 concentrations at a level that made the world substantially warmer than it otherwise would be.
    The Kayopo Indian people with their Terra Preta soils were no carbon Saints, lake sediments show us a 5 Gt Carbon draw down with their demise. Genghis Khan’s Empire also very “green” with a 700,000,000 ton draw down. Now disrupting agriculture by rape and pillage may not be a politically correct form of afforestation, but it works.

    Dr. Jim Hansen’s 100 gigatons of Afforestation will work, as trees have worked time and time again.
    The Black Death increased afforestation in Europe by one third, the mass death of farmers is bench marked across the Paleoclimatic climate records. The Columbian exchange, that Grand reunification of life, was not quite so deliberate, in fact quite unintentional, however the chips of life fell where they may, Losers and winners abound.

    Hansen’s Afforestation accounting for CO2 soil & forest sequestration is understated. Not giving full account for new understandings of the ecological services rendered in light of what we are learning about the Pleistocene and the Aerosol chemistry elephant in the room, way understated.

    Physicist tend to focus on the carbon, oxygen, and nitrogen contents of the organic materials. Pöhlker et al were surprised finding very high soil fungal potassium levels, up to 20 percent, in the 77 Amazonian carbonaceous aerosol samples, in the form of salts, in all but three of them. The samples were on the scale of mere millionths or billionths of a meter. The smaller the aerosol, the greater the proportion of potassium – those collected early in the morning were the smallest and richest in potassium. Larger particles contained more organic material but not more potassium. These facts suggest that potassium salts generated during the night acted as seeds for gas-phase products to condense onto, forming aerosols of different kinds. [1]

    NPP increases CO2 draw-down, sugar exudates pumped deep into soils, if we manage biomass carbon in more recalcitrant compost/humus, and really recalcitrant pyrolitic C, biochar, we moderate the Keeling CO2 curve,. More CO2 inspired, less respired from the breathing biosphere.

    The late Pleistocene to Holocene boundary shows a prestigious pedogenesis, the loess–paleosol sequences of the central and northern Great Plains record a broad peak of high effective moisture, a pedogenesis we can emulate with the bio-remediation techniques we advocate on these lists as the only economic way to reverse climate change..

    The new research concerning the ecologically limiting effects of Phosphorous caused by the loss of the Mega-Fanua means we have never seen the true vigor that forest & grass lands could have. That what we now see as “pristine” systems are but a shadow of their primary production potential. The Pleistocene megafauna extinctions resulted in large and ongoing disruptions to terrestrial biogeochemical cycling at continental scales, switching off this natural nutrient pump by a massive 98%. The megafauna diffused sodium inland and also reduced concentrations in plants near the coast. [2]
    (There is a whole parallel literature developing in the marine literature, with deep diving megafauna playing a key role in nutrient dispersal in the oceans).

    “The science says that spending precious dollars for climate change mitigation on forestry is high-risk:”
    I disagree, and Spending on atmospheric & Biospheric research is imperative.

    “We don’t know that it would cool the planet,”,
    I say historically we do.

    “and we have good reason to fear it might have precisely the opposite effect.”
    We must scrutinize these “reasons” in the light of new biospheric & hydrological cycling data.

    Holocene carbon emissions as a result of anthropogenic land cover change

    The Columbian Encounter and the Little Ice Age: Abrupt Land Use Change, Fire, and Greenhouse Forcing

    Salt Seeds Clouds in the Amazon Rainforest

    How salt in the rainforest becomes clouds

    The legacy of the Pleistocene megafauna extinctions on nutrient availability in Amazonia

    Are Nutrient Limitations a Consquence of the Pleistocene Megafauna Extinctions?

    The Trees that Miss the Mammoths

  12. The entire first half of this counter argument says THE EXACT SAME THING that N. Unger already made herself. It seems to me this author should have been less emotionally engaged, maybe he would have understood the text he tries to argue against. In the 2nd half this author pretends Unger was for or didn’t care about burning forests – which is a blatant lie. Nowhere does N. Unger make any of the claims that this person here attempts to “refute”. See here for what this counter argument really is:

  13. giovanni dorin says:

    After reading comments and all issues I’d rather say searching for reason and for major priority is just playing around. I say that earth heating process is complex and result of many human actions. Shouldn’t we start doing more than talking? All the aspects related to GWP have to be faced and solved: from deforestation till burning oil and REALY/SERIOUSLY primoting alternatives at low GWP grade. Financing research, imposing taxations, supporting manufacturers which adopt alternative solutions….
    And afterall if naturally forests are present, no matter what Unger thinks, shouldn’t they be preserved as much as possible?… for many different reasons obviously….

  14. jane says:

    The cause of climate change is, provably, not that forests have spread too far; it’s that mankind has dumped too much fossil carbon into the atmosphere. To suggest that we encourage tree-chopping to try to mitigate anthropogenic climate change is to demand that the parrots, pumas, tapirs, monkeys, etc. etc. who cannot live outside a forest should die for our sins.

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