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CO2 hurts plants

10 Jul 2019 | Science Notes

One of the stranger attempted refutations of climate skepticism hurled at us recently (on Facebook) was a 2018 Harvard study saying that rising CO2 levels were making plants less nutritious. Or rather that they were going to do so if CO2 levels kept rising; right now, the study conceded, the stuff is still the plant food it has been for at least 2.4 billion years. Indeed, a major underreported story is just how well plants have done thanks to increased CO2 in the last three decades. And that portion of the human race that depends on crops to eat. But never mind. Horseman coming soon, on gaunt horse.

To predict the outcome of almost any study on climate praised in a newspaper, ask first whether the thing studied is cute and beneficial or dangerous and disgusting. It won’t surprise you, given the mantra that everything bad can be blamed on global warming and every result of global warming is bad, to learn that while Harvard thinks rising CO2 levels will supposedly blight food crops entirely or make any wheat, rice or corn we do somehow wrest from the barren ground pasty and unwholesome, media everywhere are convinced it will definitely help nasty plants like poison ivy. And so it goes.

Reuters chipped in recently that we must stop climate change or the Parthenon gets it. And a National Post report that an Arctic fox baffled researchers by streaking from Norway to Ellesmere Island so fast last year that researchers thought she must have been on a boat, averaging 46.3km/day and on one day booking 155 km across Greenland, ended predictably “The fox’s long journey to Canada has also raised concerns over climate change” because melting Arctic ice would soon doom the foxes. But flesh-eating bacteria

We say “any study on climate praised in a newspaper” advisedly. As Matt Ridley just asked indignantly, why is no one talking about the remarkable greening of the Earth? His piece includes a dramatic image of where vegetation has increased since 1982, and it’s basically everywhere that isn’t desert. You’d think such a finding would be a front-page headline. Instead you can’t find it in the classifieds.

So what’s growing? Well, dandelions, sure. Ragweed. But also food crops. Flowers. Bushes. Grasses. Everything. Including those lovely trees everyone’s always going on about.

Including Swiss researchers who say that if we grew more trees it might help fight global warming, and that we could grow as much as 4.4 billion hectares of continuous forest globally, up from 2.8b now. Moreover, the study says, 0.9b hectares of new forest could be grown on land not currently being used by humans. (At least not very much, we presume; humans are ubiquitous outside the most hostile parts of the planet and one doubts Antarctica is a candidate for forestation.)

As for how you’d go about growing more trees, well, greenhouse owners could make a suggestion. On the basis of which we already are growing more trees thanks to increasing atmospheric CO2. The difficulty with the Swiss study, though, is that taking the role of CO2 in promoting tree growth seriously might eventually lead people to notice that climate consists of complex feedback loops. Including for instance that if we manage to grow so many trees that we suck CO2 out of the air in measurable amounts it might cause trees at high altitudes or in dry zones to, um, die from lack of a certain essential plant nutrient. Thus while pouncing on this story the BBC noted that “other researchers say the new study is ‘too good to be true’.”

The same cannot be said of the Harvard study, which also underlines that too often the second question to be asked of climate findings praised in a newspaper ought to be whose time machine they borrowed. The study’s release had the gall to say “Rising levels of carbon dioxide (CO2) from human activity are making staple crops such as rice and wheat less nutritious” and “more than 2 billion people worldwide are estimated to be deficient in one or more nutrients”. Here the study does a strangely double-jointed version of the time warp. Present-day malnourishment is caused by historical poverty (and is, mercifully, declining), not CO2. But the study attributes it to atmospheric changes that haven’t happened yet: “It has been shown that higher atmospheric levels of CO2 result in less nutritious crop yields, with concentrations of protein, iron, and zinc being 3%-17% lower when crops are grown in environments where CO2 concentrations are 550 parts per million (ppm) compared with crops grown under current atmospheric conditions, in which CO2 levels are just above 400 ppm.” And 550 ppm is some decades away if it ever happens. But the malnutrition is already here.

The study authors might have added, if they were interested in accuracy, that when 550 ppm comes, if it ever does, the world will be far richer and malnutrition much reduced on current trends. Unless climate policies succeed in shutting down energy affordability and economic growth.

At most, this finding only shows that crops may become less nutritious, though more plentiful, if there’s a further 33% increase in atmospheric CO2 and no adaptation in the form of new genetic varietals that exploit the extra CO2 even if one accepts that plants that evolved with far higher atmospheric CO2 are somehow unsuited to it. The mention of two billion malnourished people is a lurid piece of misdirection. And the notion that CO2 at 550 ppm is bad for plants is one that would astonish dinosaurs or greenhouse owners. Or trees.

2 comments on “CO2 hurts plants”

  1. Great article. It is interesting to note that Ontario’s Ministry of Agriculture recommends green house farmers maintain a CO2 concentration of over 1000pm. They even provide instructions on how to do this. Looks like we have been eating vegetables grown under these condition for many years and I haven’t noticed a drop in nutritional content.
    Btw the NP should publish the Der Speigal article

  2. Sorry for the Swiss researchers, but their tree planting is already debunked : http://blogs.discovermagazine.com/crux/2019/07/10/reforestation-climate-change-plant-trees/#.XS4AQ-hKjIU It's very hard to do something good these days, even planting a tree gets commented.
    And have you heard what our newest climate change scientist have to say? : https://www.independent.co.uk/life-style/prince-charles-climate-change-crisis-daily-telegraph-royal-family-a8950096.html
    So, what do we do? Believe the doomsayers and give up or treat the whole climate debacle as irrelevant noise and live our life to the fullest as it was meant to be? I sincerely hope that everybody will choose for the latest. I certainly do!

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