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Science

Does More Carbon Dioxide Mean Increased Crop Water Productivity? (arstechnica.com) 173

An anonymous reader points us to an Ars Technica report: For the most part, we think of rising levels of carbon dioxide as an environmental problem. But atmospheric CO2 can also boost agricultural productivity by helping plants grow. How do these potential issues balance out? In an investigation recently published in Nature Climate Change, scientists have looked into the global implications of carbon dioxide's ability to enhance agricultural productivity. Increased levels of CO2 can enhance photosynthesis and reduce leaf-level transpiration, the process by which some of the water that plants draw from the ground gets released back into the atmosphere. These changes can reduce growing seasons and water loss. The result could be an increase in what's called "crop water productivity," i.e. the amount of food produced for each unit of water expended. If elevated CO2 levels increase crop yield and reduce water consumption at large scales, this could help ensure water and food security despite the climate disruptions. By combining data from a massive network of field experiments and global crop models, the scientists claimed that depending on the crop type, global crop water productivity will increase by 10 to 27 percent by the 2080s. Arid regions exhibited large increases that were based on crop type.
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Does More Carbon Dioxide Mean Increased Crop Water Productivity?

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  • by Anonymous Coward on Monday April 25, 2016 @02:45PM (#51984863)

    It sounds good that crops will be more productive. So will other things, though. There was an experiment in which poison ivy was grown in higher CO2 conditions. It grew better and produced more urushiol (the stuff that causes you to have an allergic reaction). Crops may grow better, but so will weeds. It wouldn't surprise me if that included some invasive weeds like kudzu. If it stays warmer, pests might not die off in the cold; the mountain pine beetle is an example. Furthermore, there's not only increased temperatures and longer growing seasons; rainfall patterns will shift, too. Areas that currently grow crops might become arid and either have to grow different crops or not be productive at all. Other areas, such as the northern US, are likely to become wetter. Maybe you have longer growing seasons in some areas, but I'm not sure how much of a real gain there will be if the rainfall moves poleward with the warm temperatures.

    • Most of the pine beetles were killed off in a heavy freeze a few years ago.

      The reason why your example is bad is that even a rise of a few degrees C in temperature ON AVERAGE, does not mean you will not continue to have heavy cold snaps in areas like the mountains - and it only takes one such to kill back a large number of beetles.

      Also trees getting more CO2 and warmer temperatures grow better and thus resist insects better also.

      It's absurd to claim the offset in the ability to grow ANYTHING is offset entir

      • by CanadianMacFan ( 1900244 ) on Monday April 25, 2016 @03:40PM (#51985233)

        Of course there is the fact that some crops are not as nutritious when grown in an environment with an elevated CO2 level. This study tested certain crops with the expected CO2 level at the middle of the century and found:

        "Wheat grown in high CO2 levels had 9% less zinc and 5% less iron, as well as 6% less protein, while rice had 3% less iron, 5% less iron and 8% less protein. Maize saw similar falls while soybeans lost similar levels of zinc and iron but, being a legume not a grass, did not see lower protein."

        http://www.theguardian.com/env... [theguardian.com]

      • by Mashiki ( 184564 )

        Most of the pine beetles were killed off in a heavy freeze a few years ago.

        Not to forget either, that there for years they were trying to figure out what to do with all that "blue wood." Since the pine beetles streak the lumber, seems that there's a growing market for the stuff especially among the rich and well off these days and they're selling it at a premium. Now if only the cold would actually kill the ash borer beetles it would be a good thing.

        On the other hand, after ~35 years we're finally starting to see growth and good growth of birch trees and elm trees after a double

    • Re: (Score:2, Informative)

      by Anonymous Coward

      Exactly, the whole system interactions are the real question. Rubisco, the carbon capture enzyme in photosynthesis, isn't too efficient of an enzyme. It tends to grab O2 more than it should when it wants CO2. This is why C4 plants like corn, which have a mechanism to improve the carbon capture, tend to have better yields than C3 plants like wheat, and also why there have been efforts to use genetic engineering to re-create the C4 pathway in C3 crops to increase their yields, like the C4 rice project (whi

    • The need of plants for soil, and the effects of shifting climate areas on soil availability are really over-ignored.

      When the area with the correct climate for plant Foo shifts, well guess what? The new area does not generally have the right soil for that plant. Even if over-all conditions improved for plants from the geologic perspective, that would still mean thousands of years of decreased productivity while everything adapted to new conditions, and soils rebuilt.

      Stable ecosystems are more productive than

  • by AdamThor ( 995520 ) on Monday April 25, 2016 @02:51PM (#51984905)

    I've got a planted freshwater aquarium. In addition to good lighting and appropriate fertilization, people who like to keep this kind of aquarium tend to inject carbon dioxide to keep the plants growing well. The difference in plant performance in the aquarium with and without CO2 injection is substantial.

    • Do you have fish in there?
    • Raising the CO2 level in a greenhouse has major effects on growth rates. Pot growers and other hydroponics operations have been doing this for years.

      -jcr

      • by pi_rules ( 123171 ) on Monday April 25, 2016 @09:51PM (#51987083)

        I come from a greenhouse family, and I remember using CO2 generators in the 90's briefly. I asked about this a few months ago and they quit because it prompted too much growth in some crops so they nixed the idea.

        The reason I asked the question is I was coming back from a small class put on by MSU Extensions (Eric Runkle lead it) about LED lighting. He briefly touched on CO2 generation and it was basically a toss out of... "Yeah, we used to suggest that but ambient is now over 400ppm, so if you think you're low just crack a vent. I've seen some greenhouses down to 200ppm. Impressive they had it that sealed up, but just vent and you'll come back into the 400's." -- paraphrasing a lot there. I didn't take notes.

    • by romco ( 61131 )

      I've got a planted freshwater aquarium. In addition to good lighting and appropriate fertilization, people who like to keep this kind of aquarium tend to inject carbon dioxide to keep the plants growing well. The difference in plant performance in the aquarium with and without CO2 injection is substantial.

      Back in the 70s (Im #$%b old) We used to grow psilocybin mushrooms in aquariums. By injecting CO2 you could get mushrooms the size of a small pizza.

      • by Aighearach ( 97333 ) on Monday April 25, 2016 @04:35PM (#51985629) Homepage

        Carbon is a main limiting nutrient for most types of fungus, or at least for the basidiocarps.

        It is a lot easier to just mix a carbon source into the food. They don't breath the carbon in; the microbes in the feed have to capture it for them, since your shrooms were not mycorrhizal. If they were mycorrhizal then the plant could capture the carbon for them, but that doesn't include anything in the Psilocybe genus.

      • by KGIII ( 973947 )

        Heh... I haven't had any good Boomers in ages. We once stuck a thick ranch dip on 'em and put 'em between two pieces of homemade bread and ate 'em that way. I must say, they were tasty. "Go on, have a bite..." We must have walked around with who knows how many sandwiches for the better part of a week. :/ Good times, good times. I don't think most of that lot made it to the dehydrator.

  • I was wondering if someone could explain the reasoning behind these statements in the article:

    As temperatures go up, glaciers melt and ocean levels rise. Climate change also exacerbates water scarcity worldwide.

    Why would water become more scarce? Water weather evaporates more water, sure. But it also saturates the atmosphere and comes back down again. Many of our planet's warmer climates near the equator aren't exactly dry. Whether or not an area is a rainforest or a desert seems to have to do more with geography than anything else. Am I missing something, or is the article just making an unfounded assumption?

    To be h

    • by halivar ( 535827 )

      Off the top of my head, I'd imagine they mean fresh water scarcity, as higher ocean levels could overrun natural fresh/salt transition zones and contaminate fresh water supplies.

      • Off the top of my head, I'd imagine they mean fresh water scarcity, as higher ocean levels could overrun natural fresh/salt transition zones and contaminate fresh water supplies.

        All scarcity is inherently localized in context.

    • The problem probably isn't about the total amount of water, but rather, the distribution of it. Areas that have shortages of water would have more severe shortages.

      As for why it would be a net bad thing, it would be that the changes happen faster than evolution can keep up. That might also include humans, or a large portion of our population.
    • by tnk1 ( 899206 )

      I think there are some places where increased warming would make arid areas even more arid, such as the growth of the Sahara Desert.

      But I think it will be uneven. Some places will get more moisture, and some places will get less. Basically, in those places where warming has already created a desert, expect that the effect will be magnified. Where it has increased rainfall, it will further increase rainfall.

      • Isn't the Sahara greening? [nationalgeographic.com]
        • by Mashiki ( 184564 )

          This has been an increasing trend in most deserts since we've been monitoring them, and since it's already known that deserts are cyclical in most cases going from forests, plains and so on to deserts and back again, it shouldn't be a surprise. Especially since we're still coming out of the previous ice age.

    • Re: (Score:2, Insightful)

      by Anonymous Coward

      Globally, water will not become more scarce unless we boil some past the Van Allen belts (not sure how hot it would have to be for that) or launch it to Mars. The point of concern that is often portrayed as "water scarcity" is "potable water scarcity," the reduction in available drinking water as some of the normal sources fade. Many clean rivers start from mountain meltwater that is restocked with snow each winter. If the winters are insufficient to create such a bank of snow on the mountains (too rainy

    • There are many areas of the world that depend on glaciers to feed rivers in order to supply them with water during the dry season. For example India, Pakistan, and California (though this could just be snow packs and not glaciers). As the glaciers and snow cover has been shrinking there has been water shortages causing people to tap into underground aquifers at an unsustainable rate. Once the glaciers are gone the rivers will dry up except for the rainy season (the monsoon season in India which due to cli

      • An excellent point, thank you.

        Also, thank you for realizing that I was talking about *fresh* water, and not a decrease in the global water supply, for what I hope would be blindingly obvious reasons. /facepalm

    • To be honest, I've never quite figured out why slightly increased global temperatures is necessarily a net bad thing, assuming we don't see some catastrophic runaway greenhouse effect, of course.

      Mostly because we've built our society---and other stuff has adapted---around what the climate more or less is now. If it changes rapidly, life will go on (probably with a few extinctions), people will survive and so on, and everything including us will re adapt, but it likely won't be cheap, pleasant or easy.

      while

  • by OrangeTide ( 124937 ) on Monday April 25, 2016 @03:12PM (#51985057) Homepage Journal

    will this reduce the need for fresh water by the same amount lost to salt water inundation from global warming?

  • by DriveDog ( 822962 ) on Monday April 25, 2016 @03:13PM (#51985063)
    Some weeds grow faster as well, which might lead to more herbicides. Also, poison ivy grows better with increased CO2, which in my book is a bad thing.
  • What about the biomass decay from all that extra food we'll be throwing away? What's the point of growing more if we're just going to let it rot [reuters.com]? We don't suffer from food shortages, we suffer from de facto food rationing. The CO2 thing? Replace the hydrocarbon fuels with something else. The only impediment there is the political corruption.

  • Higher CO2 levels mean more plant growth across the board. Farmland, rainforest, kelp, tundra, savanna grasses, you name it.

    -jcr

  • Nutrients declining (Score:4, Interesting)

    by Maxo-Texas ( 864189 ) on Monday April 25, 2016 @03:37PM (#51985205)

    Measurable nutrients from food has declined by up to 40% since the 1930s and by about 15% since 1950.

    The water content of fruits has exploded (most fruits are basically packed nutrientless water and sugar).

    Faster growing crops boosted by CO2 will have even less time to draw as many nutrients from the soil.

    We really should measure a random sampling of end consumer food products for nutrients each year and then require current real values to be on the food labels. Monsanto, Conagra and others spend millions to prevent that kind of labeling however. And do everything they can to muddy what organic and natural means.

    But you can't trust organic and natural either outside of constant testing. Farmers want to make money- they'll try something "organic" which is actually unsafe.

    So send agents to stores to buy food and then measure it. Then post the results on the web and require each seller to use that nutritional data on labels for their food until the next test.

    • Measurable nutrients from food has declined by up to 40% since the 1930s and by about 15% since 1950.

      That's why I bought a fancy masticating juicer. I can get the same nutrients out of this New Food by simply separating the nutrients and water from the fiber. That way instead of eating a plate of vegetables, I can drink a glass of three times as many vegetables, without getting full on the fiber.

      Organic + megafarms introduces risk, as you allude to. However, in the current market conditions, "organic" often means "not a factory farm" and it also often means "heirloom variety with traditional nutrient profi

      • Aye, and adding to this is the modern method of making bread is very different. Given positive results by celiac patients tested with traditional bread making methods, it's possible that a lot of our gluten intolerance issues are due to grain preparation methods.

        For example, the modern process developed in 1961 makes bread in less time from lower quality wheat.

        https://en.wikipedia.org/wiki/... [wikipedia.org]

        The Chorleywood bread process allows the use of lower-protein wheats and reduces processing time, the system being

        • I grew up eating only home-made whole wheat bread, (raised by "health-food-hippies") and the store bread was so different that it didn't even taste like bread to me... and what I ate didn't taste like bread to my friends! Luckily in my region most of the wheat is high protein, so the local smaller bakeries aren't motivated to use Chorleywood process other than in the "crusty" European-style breads. I can find a good traditional bread, but it takes some work and attention. Obviously for people who buy only t

  • Probably not (Score:4, Informative)

    by aepervius ( 535155 ) on Monday April 25, 2016 @03:39PM (#51985223)
    There are diminishing return at some point, and other elements begins to be a limiting factor : nitrogen fixation and phosphorus for example. So it *may* produce some better plant growth some places, but for our agriculture it sounds doubtful.
    • I would argue just the opposite- for 'our agriculture' we overdue the phosphorus and nitrogen- so much so that waterways get polluted. The limited nutrient is CO2.
  • If one gives more CO2 to a potato plant does the plant grow more foliage and also grow larger or more potatoes? I suspect that many plants will actually grow less of the desired part of the plant and more useless parts, in many cases. Grass like plants probably would do well with a bit more CO2. But we would need some serious science studies to get a handle on this notion. We have a tree in Florida that is considered a non-native plague. The Malelucca tree sucks water from the earth like non
    • Photosynthesis takes water, carbon dioxide and light and transforms it to sugar and oxygen. Theoretically the fruiting bodies of plants as well as tubers in plants like potatoes would increase in yield if photosynthesis can yield more sugar. But in what proportions I do not know. Generally fruits and tubers are the result of a plant having excess energy and resources in order to propagate itself (flowers, fruits and seeds are all very energy intensive for a plant).

      With invasive species. I wonder what the Ea

    • Right, everything that is growing well somewhere now? Something else will grow better there. And the new land where the thing growing now would grow better? It doesn't have the soil makeup for that plant to thrive. Weeds (figuratively) will take over; literally, a smaller number of plants will replace the diversity that exists now. And then over time, they will re-diverisfy into new forms that replicate the prior niches.

      So many people are not considering the soil, but it is the most important thing in this.

  • ...so I've been flooding the house with pure oxygen. It also keeps everyone else in the house super healthy because its so nutritious.

    My alarmist neighbor said that the house would go up in fire within a week. And that was TWO WEEKS AGO. Oops! Oh, it looks so burned up in here, right? I can smell the smoke as I type this! Ha ha! Still here, libtard!

    I also unplugged the refrigerator yesterday to save on electricity. The wife said that all these bad things would happen, like the milk would be sour by now. W

    • pro-tip: pure oxygen will make your cigarettes taste better.

      • You know what? My doctor said years ago I'd get lung cancer from smoking. He kept saying, those things are going to kill you, you'll get lung cancer!

        So now that it's years and years later, of course he's flip flopping and saying it's emphysema that's killing me. And before that, cigarettes are what the doctors said they ordered!!! This is all just to force their radical pro-lung agenda and so of course they have to make up this stuff as they go along!

        [Pauses to light bong...]

    • 100% O2 at 1 atmosphere will burn out your body with horrendous amounts free radicals.

  • meanwhile acidification kills the ocean ecosystem. that is one of my biggest complains about carbon pollution, not the exaggerated "climate change" claims

  • by estitabarnak ( 654060 ) on Monday April 25, 2016 @04:28PM (#51985589)

    Free-Air Concentration Enrichment studies such as soyFACE artificially raise CO2 (among other variables) and monitor plant response. SoyFACE, as the name implies, is focused on soy, an important food crop. Imagine a crop field surrounded by CO2 sprayers and heaters to simulate elevated CO2 and its effects.

    Findings from the experiment include that increased temperatures will likely reduce yields of soy, even at elevated CO2. Higher average temperatures also increased susceptibility to herbivory by the Japanese beetle.

    A related meta including 228 experimental observations found that barley, rice, wheat, soybean, and potato all have lower protein content at elevated CO2.doi: 10.1111/j.1365-2486.2007.01511.x

    14 years of publications can be found here: http://www.igb.illinois.edu/so... [illinois.edu]

    In short: even if water use efficiency were to increase, that does not result in increased yield, or crop quality.

  • Why don't plants grow on Venus? Loads of CO2, right?

    Aside from CO2, plants also need a certain amount of humidity, not too much, not too little.

    Plants also need the correct temperature, not too hot, not too cold.

    Then there is the matter of wind.

    Rapid global warming, and rapid climate change, is not good for crops, far from it. Ask the California farmers who fought the recent drought. An overnight freeze can ruin tons of crops.

  • Yes, somewhat higher CO2 concentrations can help plants to grow if everything else stays constant. But everything else isn't constant.

    Most places that currently grow food stand to face much more frequent drought conditions with a higher global average temperature, and the effect of those droughts far outweighs the mild impact of higher CO2 concentrations.

    The specific impacts are regional, of course, but globally the impact of global warming is to drastically reduce crop yields. Some of this will be offset

  • More CO2 means higher average atmospheric temperatures. That, in turn, means a greater capacity for the air to hold water.

    The end result is that it rains less.

    Plants need water.

  • global crop water productivity will increase by 10 to 27 percent by the 2080s

    Too bad at the same time population will have increased of much more than 27%. And we do not know how water supply will have evolved at that time.

I've got a bad feeling about this.

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