Study: Deforestation long overlooked as contributor to climate change


ITHACA, N.Y. – When it comes to tackling climate change, the focus often falls on reducing the use of fossil fuels and developing sustainable energy sources. But a new Cornell University study shows that deforestation and subsequent use of lands for agriculture or pasture, especially in tropical regions, contribute more to climate change than previously thought.

Deforestation for the use of clay in the Brazilian city of Rio de Janeiro. The hill depicted is Morro da Covanca, in Jacarepaguá Credit: Alex Rio Brazil

The new paper, “Are the Impacts of Land Use on Warming Underestimated in Climate Policy?” published in Environmental Research Letters, also shows just how significantly that impact has been underestimated. Even if all fossil fuel emissions are eliminated, if current tropical deforestation rates hold steady through 2100, there will still be a 1.5 degree increase in global warming.

“A lot of the emphasis of climate policy is on converting to sustainable energy from fossil fuels,” said Natalie M. Mahowald, the paper’s lead author and faculty director of environment for the Atkinson Center for a Sustainable Future. “It’s an incredibly important step to take, but, ironically, particulates released from the burning of fossil fuels – which are severely detrimental to human health – have a cooling effect on the climate. Removing those particulates actually makes it harder to reach the lower temperatures laid out in the Paris agreement.”

She said that in addition to phasing out fossil fuels, scientific and policymaking communities must pay attention to changes in land use to stem global warming, as deforestation effects are “not negligible.”

While the carbon dioxide collected by trees and plants is released during the cutting and burning of deforestation, other greenhouse gases – specifically nitrous oxide and methane – are released after natural lands have been converted to agricultural and other human usage. The gases compound the effect of the carbon dioxide’s ability to trap the sun’s energy within the atmosphere, contributing to radiative forcing – energy absorbed by the Earth versus energy radiated off – and a warmer climate.

As a result, while only 20 percent of the rise in carbon dioxide caused by human activity originates from land use and land-cover change, that warming proportion from land use (compared with other human activities) increases to 40 percent once co-emissions like nitrous oxide and methane are factored in.

“In the short term, the land use tends to have twice the radiative forcing as it should have had from the carbon dioxide because of the co-emissions, so it’s twice as important,” said Mahowald.

Mahowald’s finding resonates with a previous paper she published in Global Biogeochemical Cycles in January, “Interactions Between Land Use Change and Carbon Cycle Feedbacks,” which showed that the carbon released by a deforested area is actually doubled over time because that area’s future potential to function as a natural sink – i.e., a habitat that can absorb carbon dioxide from the atmosphere – has been eliminated.

“Normally people only think about what’s happening right now when they think about the carbon budget,” Mahowald said. “But if you think about what’s going to happen over the lifetime of that land, long into the future, you should multiply that land conversion by two to understand the net effect of it.”

As agriculture expands in tropical areas and the pressures to turn forest into croplands increase, Mahowald stresses the importance of using extended timelines to assess the impact these practices have on the climate.

“We have a nice phrase: multi-centennial legacy of current land-use decisions,” she said. “When we think about climate change, we can’t stop at the end of the century. The consequences keep going for a couple more centuries.”



86 thoughts on “Study: Deforestation long overlooked as contributor to climate change

  1. I thought someone would get around to this …..sometime after Borneo and the Amazon are turned into parking lots.

    • This is urban heat island effect and rural cold island effect. These are discussed in my book “Climate Change: Myths & Realities”, 2008 — Chapter 7: Ecological changes –.

      Dr. S. Jeevananda Reddy

    • The Amazon is just fine, as the people are moving out of the jungle to the cities and the jungle is raging back quite nicely. It’s in Indonesia and the area that the forests are being cut down for palm oil/biofuel productions.

      It is quite clear that CO2 cannot and does not warm the climate and, thus, efforts to decrease emission with stupid and costly biofuels programs need to cease. The current ethanol production by Brazil, China and the US are all patently waste of effort, particularly in the US where perfectly good food (corn) is used to make ethanol.

  2. I guess we’ll have to stop growing food to feed ourselves. We’ll have to “save the planet” by returning all agricultural and pasture land to Mother Nature.

    But a lot of Americans and people in other developed nations probably need to go on a diet anyway (sarc).

  3. And a fair part of these “land use changes”, especially in Indonesia, are due to biodiesel production.

  4. The most environmentally friendly solar energy converter is a tree. From them we get so many other useful products, and as opposed to killing wildlife they tend to provide habitats.

  5. The short version of this paper is “It’s worse than we thought”. But this time, the “it’s” does not refer to CO2.

  6. When I told a buddy that the ice cap on Kilimanjaro retreated due to deforestation downslope rather than from warming air, he said that just proved his point that humans are responsible for “climate change”.

    • Gloat, let ’em claim climate change… The big kahuna is warming. The paradigm of AGW is all that needs to be taken out. “Climate Change” doesn’t impress anyone; “Global Warming” does.

      • Gloateus, I would argue your friend is somewhat correct, not because of CO2 but man does have an effect on local/national climate (farms, cities, forestry, etc). The root cause and the best way to prevent deforestation is through ending energy poverty, poverty in general and corruption. You should have argued with your buddy, the best way to save forests/environment used for building materials and food cooking is to allow them use fossil fuels. If a society can make concrete, steel and gas/electricity for cooking the natural resources would not have to be plundered as much. With energy independence, more resources could be used to end corruption and improve living standards.

  7. Perhaps someone would care to put together a brief but total argument which can be used to try to convince unbelievers. It has to less than two A4 pages and start in the Pre-Cambrian. It must refer to the earliest ice ages, Carboniferous coal, Cretaceous chalk deposits of the Zechstein Sea, evolution of modern plants in a CO2 rich atmosphere, plate tectonics, the Drake Passage, the slow lead into the Pleistocene, increasing amplitude of the glacial periods of the last half million years, the constant temperature maxima of the interglacials, the CO2 lag behind temperature, the sea level lag behind both. A few odds and ends and it should be convincing. Leave technical words to a bare minimum.

    • The clincher for the general public is the Big Lie about “97% of all scientists”, which can’t be shown bogus in so few words.

      • Gloat, i think the easiest way is to point out that ALL prominent skeptic climate scientists are part of the 97%…

      • Are ‘they’ ABSOLUTELY sure that the number isn’t 96%? Or maybe its 97% but none of them are scientists.

    • There is no need to convince unbelievers.


      Nobody who sent astronauts to the moon, cared about convincing flat earthers

  8. Not just deforestation. How about millions of acres of plowed tilled black soil to soak up the suns rays and quickly melt patches of snow where as 150 years ago, not much there but prairie grass which isn’t black!!!

  9. plant some trees… who was the Aussy professor who got stuck in the Antarctic ice a few years back Chris Turney, a professor of earth sciences at the University of New South Wales. Had to call in to have a couple of ice breakers to help. He got the business from other scientists. Turney’s decided to plant a bunch of trees to reduce the carbon foot print caused by his expedition…
    21 January 2014
    From the section Science & Environment…

  10. ironically, particulates released from the burning of fossil fuels – which are severely detrimental to human health – have a cooling effect on the climate

    Settled science.

      • This Solar Gloom effect has been known about since the 70’s and the point you raise is an established and obvious fact that I’ve been making for some time, ever since Hansen effectively agreed with this. It must be a significant proportion of the cause of warming because Hansen himself implies that this! Why and how? Because, in his desperate attempt to defend and explain the recorded divergence of temperature rises from rises forecast by CO2 driven CAGW theories, he published a Paper following his researches to determine the reasons for this. He agreed that this flattening out had occurred, but his “research” explains that this flattening was due to the Solar Gloom cooling effect from increasing particulate carbons and sulphates in the atmosphere from increasing emissions in recent years of Chinese Power Station emissions. As you’ve explained, he clearly shot himself in the foot armed with his own gun and ammunition as his new theory implies that temperatures rise following and during a reduction of Solar Gloom effects during the recent periods of USA/Europe’s reductions in particulate carbon and sulphate emissions. Not only does this discredit the CO2/temperature theories and long term graphs of the CAGW supporters but also even implies that sulphates and particulate emissions have far more effect on temperature than CO2, i.e. they are shooting at the wrong animal, and spending $billions doing it!

  11. Guess what? If humans caused the deforestation, then the deforestation can be labeled “anthropogenic.” So, deforestation is therefore one of the contributing factors of “AGW” (Anthropogenic Global Warming)

      • Most likely doesnt. Has anyone got an estimate of an acre of land with mature forest CO2 uptake against an acre of grass or crops. Seems to me the leaf area alone of fast growing crops or grass over an acre would far exceed that taken up by slower growing mature trees. Is there an estimate of the actual amount of foliage bulk produced.
        “Mahowald’s finding resonates with a previous paper she published in Global Biogeochemical Cycles in January, “Interactions Between Land Use Change and Carbon Cycle Feedbacks,” which showed that the carbon released by a deforested area is actually doubled over time because that area’s future potential to function as a natural sink – i.e., a habitat that can absorb carbon dioxide from the atmosphere – has been eliminated.”

        Eliminated? Dont think so madam, even if it is just producing weeds the area is still absorbing CO2 if plant life of any kind exists there.

      • If deforestation causes climate change then REforestation must reverse the process. Problem solved!

        Well the reforestration has been going on here for more than hundred years already. We get more wood in the forest every year, and ‘you guys’ tell us we may not use it because Drax and deforestration and all the wrong reasons.

    • Except it’s all nonsense. Deforestation doesn’t cause global warming, any more than burning fossil fuels does. Forests are important for other reasons though, so shouldn’t be cut down willy nilly, such as for biofuels to “save the planet”, or to install gigantic, land-hogging solar and wind farms, also to “save the planet”.

  12. IPCC AR5 table 6.1 shows net land use change as 180 GT +/-80GT and residual land sink as 160 Gt +/- 90 GT. The uncertainty bands are as large as the numbers. More figures pulled out of some computer modeled programmed PhD butt!

  13. Just a mom here, reading up on climate change and hoping there is hope for the future. North American Indigenous communities have stories about how settlers changed the climate by clearing the trees. We are so used to living out of tune with nature, making nature adapt to us, instead of us adapting to nature. How does the average citizen help to make things better?

    • How does the average citizen help to make things better?

      By not inundating our kids with baseless doom and gloom. Also, by collecting garbage. I do it whenever I take a stroll in the woods.

    • A. The climate has been changing since the planet’s beginning. In the Cretaceous (age of Dinosaurs), there were no ice caps, the greenery was lush – a garden of Eden from one end of the earth to the other. Average temperature was about 10C higher than today. The tropics were not hotter than they are now. The open ocean cannot get hotter than 31C roughly little changed today (At 31, the seawater evaporates cooling the surface and the water vapor rises because it is lighter than dry air, forms clouds and cooling rains fall as the day progresses and the sun brings the surface water temperature up towards its maximum 31C. The formation of the clouds then follow, which reflects the sunlight back out into space. This system works like a thermostat.

      From the 1950s to the 1970s, the earth was cooling and some of the same alarmist scientists were certain we were causing an ice age with our pollution and forecasts of mass starvation, crop failures, wars, pestilence would wipe out civilization. These kinds of scares have been going on for a few centuries. Google the Little Ice Age that lasted from ~1400 to 1850. A third of Finnlanders died of starvation, the Vikings had to abandon “Greenland” where they raised cattle, sheep, planted grain etc. Today some of these old farmsteads are just appearing from under the melting ice! During the War of Independence, the sea froze all the way down to New Jersey and Washington’s men rolled cannons on the ice from a warehouse in Manhattan down to the coast of New Jersey to get them away from the British. The Bosphorus in Turkey froze over and the Thames froze and people had fairs and winter sport on the ice. New Yorkers walked on ice from Manhattan to Staten Island.

      Five hundred years before that in the Middle Ages, it was warmer than now. Scotland even grew grapes and had a wine industry. The economy of Europe boomed. The Dark Ages in 500-700 was cold and miserable and people subsisted miserably. Warm -good for humankind -civilization economy, farming, learning, Cold- terrible, starvation, ignorance, decline. The Roman Warm Period, warmer than the Middle Ages – great civilization, economy good, etc. etc. 8000 years ago was the “Holocene Optimum” the peak warm period after the end of the glacial period 10,000 years ago. It has been cooling on average for 8000 years as we head for the end of the Holocence interglacial. Warm interglacials 10,000 to 20,000yrs duration, glacial periods ~100,000 years with ice up to a kilometer thick over todays Chicago and New York (3 kilometers thick in Canada.

      Dear Mrs A. be of good cheer. The fear and alarm is totally bogus. The warming and CO2, which are good (check the growth in agricultural output per acre over the the last 40 years). The planet is regreening with 14% increase in earth’s forested areas – most notably in dry regions (Google NASA greening of the planet). Hurricanes, tornadoes, drought, floods are all no worse than they have ever been. It is a big fear program. Even if we continue what we are doing, the CO2 and warming, which wouldn’t even reach +2C degrees in a hundred years, are both good. The population of the earth has been slowing and will peak at ~9Billion by 2050 – we are 85% there. It will be a land of plenty and prosperity for all if we can only stop all the nonsense political stuff and stop wasting trillions that we need to make the world a better place. The climate is going to be just fine. Study up every aspect of it, question everything in connection with it. Delve into the political cause of all this alarm. Start by not being afraid.

  14. I thought Pielke Sr. looked at this a decade ago. A link to his site is on the right under Lukewarmers.

  15. One might think that more sequestered CO2 has been lost from soils, due to agricultural practice, than has been lost from deforestation.

    As a side note, it’s been well known for years that more trees are growing in North America right now, than at any time since European settlement began.

    • At least, more trees were growing here before the great deforestation of the Southern US forests began, in order to annually feed several million tons of wood pellets to Drax power station in England.

    • I wonder how many maple trees were in Canada 22000 years ago. Or how many trees of any species, for that matter. Any guesses? Mine is 0.

  16. 1) cut down forests to plant oil palms for biodiesel.
    2) Diesel is killing people so scrap it and the East Indies and Africa must cut down the trees they planted after disrupting human and animal habitat. Take a homeless orangutang to lunch.
    3) shut down coal and import wood cut down in North Carolina to UK to burn.
    4) cut down trees and plant corn to burn
    5) cut down a National Park in Denmark and scarxce wilderness in UKand erect windmills.

    Alternatively the planet on its own, using CO2 generated by fossil fuels has increased world forest area by 14% and the existing trees have been fattened and plankton in the sea are also thriving. CO2 from fossil fuels has increased productivity of farming per acre resulting in farmlands returning naturally to forested lands.

    Yes, researchers, you have an inkling of the solution to the problem. Sceptics have been leading the way in climate science – researchers lag sceptics by 8-10 years but they are getting there.

    Incidentally, the remarkably expanded forest growth and plankton growth are both sequesterers of CO2 and the activity is also endothermic!! The rapid growth occurred during a warming hiatus and trending cooling period – is that a coincidence? There are roughly 3 trillion trees on the planet (google). 14% is 420 billion trees, 14% more shade and this can be probably doubled by considering the increase in size of existing trees due to this sequestration and we will throw in the plankton.Okay. An estimate of the carbon wt in an average tree of 10 years old is 500 lbs. If the main growth was over 10 years, then the average age of the new trees is 5 years, so average new tree is 250 lbs.

    So 420 new Giga trees multiplied by say two to account for that added onto existing trees, throw in plankton to be conservative. 840 G trees, multiplied by 250lbs, lets say 0.10 metric t.

    840 Giga x 0.10 tonnes = 84Gt of carbon.

    Man’s fossil fuel and cement emissions = ~10Gt C/yr in 2014 or 100Gt in ten years. Apparently half goes into the ocean although, maybe those voracious trees are reducing the proportion going into the ocean a bit or China and India are burning up a lot more coal, making the estimate not too bad. If the CO2 accumulation is flattening or beginning to, that would corroborate the figure and since the sequestration process is exponential, given adequate CO2 available, all the new coal in Asia, Germany, etc will keep feeding a growing sink..

    Okay, what about cooling? Certainly the energy absorbed in sequestration as a first approximation must equal the energy you get when you burn it, this would reduce the active energy budget of the planet, but I leave that calculation to others – could it have made a noticeable contribution to the hiatus?

  17. One of the things many miss is that many of the AGW crowd, certainly many environmentalists, hate all other humans and any human activity but themselves and what they do. Also the USA gets no credit for reducing our greenhouse emissions, have more forest than we did 150 years ago, and generally being the most environmentally sensitive country in history. Yet for the political left it will never be enough. They are not even bypassing the good for the perfect, they are convinced that if USA went away the world would be better place.

  18. Does anyone mind, that mankind has burned stuff way longer than since the age of industrialization, namely ever since fire was “discovered”? While the roman empire only had like 50 Mio residents, agriculture was not so efficient. Deforrestation in Europa was massive, and so it was in other places like China.
    This should have raised atmospheric CO2 levels substantially, but it did not. Why?
    The answer is simple. With a half live of 35-40 years man made CO2 will not live long enough to accumulate over centuries. Roughly 1.8% of elevated atmospheric CO2 levels get consumed every year by natural CO2 sinks. And they are scaling extremely well, as this graph shows.

    So with current output of 36Gt of CO2, we should be able to reach about 530ppm before emissions and CO2 sinks even out eventually. If we stopped all CO2 emissions right now (hopefully not), CO2 would drop to just over 300ppm by 2100. So all these stories over ever lasting CO2, once we emitted it, are just fairy tales.

      • You’re right about the goats. Man is surpassed only by the goat in screwing up his environment. I don’t remember the reference but Israel did a study many years ago where they fenced off a section of or bordering the Negev with the equivalent of chain-link fencing to keep out goats and other roaming vegetarians. After two or three years the fenced area was fairly lush with vegetation.

      • Goats and sheep are fairly destructive in their food consumption. The Mid-East and parts of Africa and Asia would do well to rein in the numbers of free roaming and wild goats and sheep.

      • I agree with you about the goats but question the sheep. The U.S. Air Force did a study many years ago on the safest way to keep the grass trimmed around their nuclear bomb storage bunkers and decided that sheep were it. According to the study sheep only trim the grass short without damage where goats tend to eat it roots and all.

      • That entirely depends on the forage they are consuming. Look at Lebanon/Syria, the free ranging goats and sheep have stripped much of that region down to nothing, and have long been going after trees and shrubs that in other regions they do not eat, especially the 1st-2nd year saplings. Older trees they go after the new growth on limb ends and the softer outer bark on roots protruding from soil and rocks. CO2, its such a tiny thing compared to everything else. Complex systems interacting, people with agendas, quite the conundrum.

  19. Animal agriculture is the number one cause of environmental damage, by far. But people need their milk, bacon and burgers so no one says anything. We need to cut our dependence on animal agriculture by over 50% or we are going to kill ourselves from the inside and the outside.

  20. Goats should be the poster child of global warming. They cause such environmental destruction and has for millennia, which has made the last interglacial last much longer than expected.

  21. Here is how deforestation can effect the climate. The image below is Europe today (on the least cloudy day I could find).

    All the brown patches are where agriculture or cities are located today. 4,000 years ago, it was mostly green.

    The brown patches have an Albedo of about 30%. 30% of the sunlight is reflected back to space, modulated by the 65% of the time that clouds are above.

    The green patches have an Albedo of about 10%. 10% of the sunlight is reflected back to space.

    But this is summer-time numbers only. In the winter, there is not much difference.

    So, all the extra agriculture and cities in the summer has probably changed Europe’s Albedo from an average 40%-45% to an average 45-50%. I have the numbers on what Europe is roughly today.

    This change is going to effect the world climate by about 0.02C. Tiny. Europe is a small part of the overall Earth and the change is not that much (keeping in mind cloudiness has more impact than land-use).

    Think about the rest of the world and one gets into an Albedo change of up to 0.3C from land-use. Forget about the fake GHG impacts.

  22. In the United States, alone, about 50,000,000 acres of land are devoted to growing Roundup-Ready monoculture corn, to make ethanol, to burn as motor fuel, to “fight climate change.” That’s more than the entire land area of the nine smallest U.S. States, combined.

    We live in a very mixed-up age, in which 50,000,000 acres of land are put under the plow for environmental benefits.

  23. Problem is “deforestation” is not a problem. New growth forest is what Gaia needs, in spite of the stupid shiite leftarded morons spew.

  24. I have never seen a study that determines if forty acres of soybeans sequester as much co2 as same acreage of forest.

    • Robert Long

      I have never seen a study that determines if forty acres of soybeans sequester as much co2 as same acreage of forest.

      It is not a trivial question, nor one easy to answer. Classic hardwood forests are near-deserts down under the trees, as the trees cut off sunlight to the forest floor and starve new growth out until forest fires and fallen large trees create a short-time open sunlight space. The large trees of course are very heavy with lots of leaf arrea. But they are few in number, with many meters between each large trunk. The many small trees previously trying to grow have all died out (been crowded out by the very successful tall trees that do survive), and so they have ALL “been converted back to CO2 by fires and by decay. (slow combustion as food for small plants and animales). But how many kilograms of moss remain after they “eat” a tree, and what are the long-term CO2 offsets for moss and fungi through a 150 year forest “lifetime”?

      The open fields around dead trees (and the few power line cuts through a forest) are the ONLY places where new growth occurs, and thus the only places where CO2 is “stored” outaide of the few large (but heavy!) trees. A commercial field is growing tons of produce and vegetation every year. What is not harvested in plowed back under as mulsch and soil for the next year – again, better living through fungi and mold. The field is annually renewed, so is continually pulling CO2/recycling CO2 from the air into feed, food, fodder, fuel, and families.

      The math – and, more importantly, the assumptions for the math – is not trivial.

      • Cropland and grassland sinks 0.3 tons of Carbon per acre per year as long as it is not tilled. This has been carefully studied in many different places and that is the general value.

        This is a higher number than forested land which is fairly low.

        Zero-till crops and grassland worldwide sink about 1.0 billion tons of Carbon per year, forests are another 1.0 billion tons and oceans sink about 2.0 billion tons. This is compared to human emissions of about 9.5 billion tons.

  25. Of course they focus on “greenhouse gases,” completely ignoring the major effects of deforestation. The effect of the loss of transpiration on rain patterns, the loss of the cooling effect of canopy shade, the changes in wind patterns…

      • The authors of this article’s paper need to see that. The linked paper explains desertification, heat waves, increased land surface temperatures, all caused by deforestation – without once mentioning the evil bugaboo of greenhouse gases. GHG’s are largely irrelevant when the focus is properly placed on the benefits of natural forest to climate. Forestland doesn’t just hold the key to hydrological cycle stability, but also surface temperature stability Localized climate changes due to deforestation may have an effect on localized concentration of certain GHGs but the minor localized change in GHG concentration is effect, not cause.

        This article is another example of misplaced focus on CO2 and “CO2 equivalent” forcings as the regulator of climate, another example of the perversion of science in the name of CAGW.

  26. I recall an article on early man in North America having s role in changing the climate in California by burning flora. Can’t seem to find it at the moment.

  27. Dr. Pielke, Sr., a very productive and ethical climate scientist, was ridiculed and shouted down for pointing out that land use changes are very important climate influences.
    Simply because he dared to challenge the CO2 obsession if the consensus.
    Now the weasels who have destroyed climate science as science, and turned it into a Lysenko style monster dare to to come back to land use.

  28. In these papers[1][2], not one mention of increased photosynthesis as it directly links to earth’s energy budget[3], exists, only the effects on land use on CO2, whose effect on climate has not been sufficiently proven in the satellite era, is mentioned.

    Photosynthesis is very efficient at transforming the visible spectrum of the TSI into something other than black body radiation, and is arguably the cause of Trenberth’s “missing heat”[4][5][6], even though the “missing heat,” itself, was not caused by CO2 in the first place[7].

    Any warming produced by the increasing greenhouse gasses in the atmosphere would be evident in the lower troposphere as a reduction in the lapse rate, especially in the tropics where their has been no significant change beyond signal noise[8].

  29. Removing those particulates actually makes it harder to reach the lower temperatures laid out in the Paris agreement.”……..

    Back in around 1968 engineers showed that not only does cleaning the air result in an actual increase in temperatures by nearly a degree but it also results in an erroneous increase in the measured temperature of nearly as much because the Stevenson screen is not a perfect zero temperature rise effect enclosure. It rises in temperature considerably more in unfiltered sunlight of the now almost unbelievably cleaner air that in the pre industrial age let alone the Victorian industrial one.

    The politicians and scientists have always had a contempt for engineers which they regard as vulgar trade and have in this case ignored their warnings of the incompetence and narrow training of climate scientists which means the scientist’s measurements are totally untrustworthy at the sub degree level. Perhaps we should have lied and over hyped the case as the climate fraternity have done and it is our fault for having the integrity not to do so.

  30. Deforestation is obviously not in the official playbook of the advocacy cabal, mainly because it’s not centered in rich countries. The UN focus is on money farming and deforestation did not make the grade. It’s much easier to buy them off than to punish them and buying them off works if deforestation is not in the discussion. The same goes with pollution and ground water depletion.

  31. Today there are more trees in the USA than there were 100 years ago.
    It is possible that this is true of the whole planet also.
    Received mantra is that trees are being lost by deforestation.
    But CO2 enrichment of the atmosphere is increasing the number of trees.
    Bond et al 2003 showed that in mixed tree-grassland ecosystems, past CO2 starvation caused a reduction in trees since tree saplings growing more slowly don’t grow big enough to survive the average interval between fires.
    Thus less CO2 = less trees, and more CO2 = more trees.

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