PBS: The Science on Planting Trees to Combat Climate Change

October 21, 2021

Science based reality check on how much trees can do for climate mitigation.

21 Responses to “PBS: The Science on Planting Trees to Combat Climate Change”

  1. ubrew12 Says:

    This video is well worth watching. The forestry scientist featured in it is doing great work. Better plant those new forests now, because they won’t start drawing down carbon for at least 20 years.

  2. redskylite Says:

    Excellent video and insight into forestry carbon cycle. Makes me wonder how much research (if any) went into biomass burning of wood-chips, as I read somewhere that trees are harvested every 3 years or so.

    Time to cherish and preserve our forests everywhere, as various movements have been fighting for during the last few decades.


    Deforestation notches up along logging roads on PNG’s New Britain Island.

    “Such systemic problems affect not only the biodiversity-rich forests and the services they provide, including clean water, carbon capture and erosion control, but also the societies that live nearby and indeed have served as stewards for generations.”


  3. Brent Jensen-Schmidt Says:

    So, a young tree takes in CO2, builds itself with this CO2, and transpires more CO2 than it takes in? BULLSHIT! Am open to information.

    • Gingerbaker Says:

      You forgot soil.

      • rhymeswithgoalie Says:

        All trees dump retired leaves and needles on the ground. I wonder if the ratio of leaf-dumping to storage is effectively higher in young trees or whether it has to do with growing in an uncanopied area.

    • ubrew12 Says:

      “Am open to information” Are you open to watching the video? My take is Arrhenius Law: chemical reactions double for each 20 C rise in temperature. New forests contain a lot of exposed bare ground, so microbes are warmer and quicker to break down organic mat’l, releasing CO2. As the canopy fills in and shades the soil, the microbes cool and work more slowly. Meanwhile, the filled in canopy is engaging in more photosynthesis, building more wood, and the forest becomes a net CO2 absorber.

      • Brent Jensen-Schmidt Says:

        Watch the video yourself. Around 4:20, ‘young forests transpire more CO2 than take in’. No they don’t, the soil transpires CO2 whilst the trees lock up carbon in their mass. The soil is there without trees, with young trees and with old trees. Am open to ACTUAL information proving planting trees is bad for the climate!

        • jimbills Says:

          Brent – the soil is essentially microbes. The microbes break down dead or discarded organic matter, releasing CO2. More matter, more microbes. I suspect a lot of the organic matter in soils in new forests is actually the rotting root systems and leavings of previously cut trees. But, as there are more plants in a new forest than an old one, it could also be that they leave more decay and leaf litter than would occur in an old forest.

          So, at least in the area studied by this scientist, there was more CO2 released than captured as the forest was first maturing, but the forest became a net CO2 sink at some point. The video says that happens after twenty years, but it probably varies from forest to forest on the exact time frame. And, its important to note the video shows the evidence from one scientist studying a limited area.

          Another example would be the Amazon rainforest. There is no fall season there, so there’s much less seasonal plant litter. An old growth section of the Amazon has very little microbe activity in the rainforest floor. It’s largely a ‘dead’ soil. It’s why farmers burn the forest there – the ash serves as fertilizer, replacing the nutrients for agriculture that would be there if the soil was full of microbes. But, the loss of the trees, leaving rotting root systems, transforms that area into a major carbon source.

          The Amazon in total is now becoming a carbon source:

          About microorganisms and soil:

          ‘Soil microorganisms exist in large numbers in the soil as long as there is a carbon source for energy.’

          There are conflicting studies on whether young trees (with more of them packed together and because they are growing quickly) capture more or less carbon than old trees (which have more mass). But, if I had to guess, the difference is entirely on what the soils in those forests are doing. If there’s a lot of organic matter in the soil, there is going to be a lot of microbe activity, and so there’s going to be a lot of CO2. The soil activity can vary greatly from region to region, so I’d bet there are different results for different areas. A likely rough guide, though, is that an older, mature forest would be less of a carbon sink than a new forest if one was just counting the trees alone, but would be much more of a carbon sink than a new forest if one was counting both the trees and the soil (as the scientist in the video is doing).

          So, it’s not that planting trees is bad for the climate – quite the opposite – it’s just that there’s a lag time before a net carbon sink (counting both the soil and the trees) kicks in. Planting trees now would be vital, and protecting older forests from logging would be vital.

          • Brent Jensen-Schmidt Says:

            Lard tundering joizes James William, such a long response is impressive. Actually read it. Have little argument with all said this post, except, planting trees is bad.
            The video’s heading is:


            It is implying, to the point of being downright explicit, that planting trees is bad for climate change. I do not agree and believe planting trees is good for CC. ‘Logic, not studies’.

          • jimbills Says:

            It’s YouTube, so a catchy title like that is meant to attract views. Imagine what the area would be if no trees were planted, though? If left alone, in an area surrounded by forest, it would eventually become forest again, but it would take longer. Theoretically, it would also take a longer time to become a net sink. So, really, planting the trees sooner than later is much better for capturing carbon.

            The video itself doesn’t say anywhere that planting trees is bad. It is guilty of using a misleading title in a fairly crass attention grab, though.

        • rhymeswithgoalie Says:

          A lot of the carbon the microbes have to work with comes from discards of trees. My personal experience with the large pecan trees around my house (large individuals with very little shared canopy) is that the leaves dropped near the trees represent higher carbon-rich debris per square foot than the ground-based plants (shrubs and perennials, with no need to mow).

        • J4Zonian Says:

          Nowhere does it or anyone here say anything remotely resembling “planting trees is bad” It says ‘a surprising truth’, you leaped to an absurd and unwarranted conclusion. Maybe you should stop doing that.

          This is yet another excellent reason and another place for applying permaculture principles. Permaculture uses succession instead of trying to fight it.
          And it strongly suggests planting, growing, and harvesting trees differently.

          First, not making large clearcuts but cutting individual trees or in small patches, considering land not just as tree farms but integrated food-fiber-medicine-material producers, with consideration for wildlife there and in related unexploited areas as well as climate.

          Second, planting a community to protect and build the soil while supporting the growing trees thus helping to sequester carbon earlier than 10 years.(20 for arid areas, as the video says.)

          Lots more can be learned from Jacke and Toensmeier’s Edible Forest Gardens, an amazing 2 volume practical and inspirational work on this exactly.

    • rhymeswithgoalie Says:

      So, a young tree takes in CO2, builds itself with this CO2, and transpires more CO2 than it takes in? BULLSHIT!

      Option 1: Assume professional researcher who is challenged for data for every journal paper she has ever published learned something counterintuitive and dug deeper in the complex system to understand and explain it, and non-experts making the video didn’t capture the concept.

      Option 2: Assume you came up with an obvious challenge to conclusions that no dedicated scientists in the field thought of.

      Am open to information.

      Scientists and professors generally like challenging questions and explaining their work down to excrutiating detail. Yelling “BULLSHIT!” at anything you don’t yet understand is just being an asshole.

  4. jimbills Says:

    I’m not a big fan of these sorts of stories, as there is invariably some sort of major hitch not mentioned, or the economics of it are so prohibitive that the idea remains forever just an idea, but I saw this today:

    • redskylite Says:

      Good find, sound very promising for the future until a non carbon based system is developed.

    • redskylite Says:

      “The aviation sector is also betting on synthetic fuels, or e-fuels, made with hydrogen produced from renewable sources of energy and with CO2 captured from the atmosphere.”


      • J4Zonian Says:

        The aviation sector will bet on anything that promises to keep aviation going instead of moving to the obviously much much much much much better choice of rail for all long-distance continental transport (including high speed rail) and being content with slower-moving non-carbon, non-combustion ships. As people somehow survived with for thousands of years. Before that they didn’t move by water at all.

        Just like the right wing and fossil fuel and other corporations have kept the US and much of the world paralyzed with hope of avoiding climate catastrophe without making any changes, the aviation industry wants to preserve its unavoidably elitist industry by using distraction, false dichotomies, traps for activists and the public (like CCS, carbon prices, nukes, etc.) and other lies, without regard for the survival of humanity. Being subject to every industry’s nonsensical anti-ecological whims and addictions is not the way we can move forward; we need to reconstitute the US government and finally allow real democracy, with strong enough government to counter the psychopaths in charge of the right and the corporate world.

  5. jimbills Says:

    On the video, it reminds me of a small forested area on some private land in DFW that has always caught my eye for its difference. The trees there are much larger than typically seen, and there’s virtually no undergrowth around them. It’s gorgeous, especially at sunset, and it’s so unusual here. Pretty much every forested area in this area has a large mix of small and large trees with a lot of undergrowth, indicating they had been cleared areas at some point in the last century or two.

    It’s not an unusual sight in Oregon, though. That state is about exactly half state and national parks. Great recommendation on the scientist’s part in the video that we should start making designated carbon reserve areas.

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