It’s not the Heat…Well, Yeah, maybe it is the Heat

October 27, 2011

We’ve heard it a hundred times – “More CO2 is good for plants.”

Agronomists and Botanists around the world have been asking food crops the question – “So how is all the extra CO2 working out for you?”


For years, as scientists have assembled data on climate change and pointed with concern at melting glaciers and other visible changes in the life-giving water cycle, the impact on seasonal rains and irrigation has worried crop watchers most.

What would breadbaskets like the U.S. Midwest, the Central Asian steppes, the north China Plain or Argentine and Brazilian crop lands be like without normal rains or water tables?

Those were seen as longer-term issues of climate change.

But scientists now wonder if a more immediate issue is an unusual rise in day-time and, especially, night-time summer temperatures being seen in crop belts around the world.

Interviews with crop researchers at American universities paint the same picture: high temperatures have already shrunken output of many crops and vegetables.

“We don’t grow tomatoes in the deep South in the summer. Pollination fails,” said Ken Boote, a crop scientist with the University of Florida.

The same goes for snap beans which can no longer be grown in Florida during the summer, he added.

“Its impact on agriculture systems, impacts on crops, mitigation strategies with soil management — a whole range of questions was being asked about climate change,” said Jerry Hatfield, Laboratory Director at the National Soil Tilth Laboratory in Ames, Iowa.

“The biggest thing is high night-time temperatures have a negative impact on yield,” Hatfield added, noting that the heat affects evaporation and the life process of the crops.

“One of the consequences of rising temperatures … is to compress the life cycle of that plant. The other key consequence is that when the atmosphere gets warmer the atmospheric demand for water increases,” Hatfield said.

“These are simple things that can occur and have tremendous consequences on our ability to produce a stable supply of food or feed or fiber,” he said.

see Dr. Hatfield’s 2009 testimony to congress below, and my own video on the “CO2 is Plant Food” crock:

16 Responses to “It’s not the Heat…Well, Yeah, maybe it is the Heat”

  1. Jean Mcmahon Says:

    I am the only one on Oklahoma who is concerned that the Farm report and the press quote Gary Mcmanus of the Oklahoma Climatological Survey reporting xtreme weather conditions in Oklahoma this summer and he Never mentions Global Warming …he always throws in a mention of La Nina as in this quote.”.The latest U.S. Seasonal Drought Outlook from the NWS’ Climate Prediction Center (CPC) gives little hope for improvement in the Southern Plains drought conditions at least through January 31st. Oklahoma remains firmly ensconced in the “drought to persist or intensify” area thanks to the strengthening La Nina in the equatorial pacific waters.” What is the job in of climatologists in the states??? Mcmanus gave a report on future expectations re GW a few years ago that was informative,but he never refers to it..

  2. That extra C02 is working here in Connecticut. I am growing 2 windmill palms in my garden- in the ground for 4-5 years.

    that 4-5 degree higher over night low in the winter, compared to 30 years ago, makes growing this species here now possible with minimal overnight protection.

  3. Orson Olson Says:

    I have studied the lab-based literature on the effect of added CO2 on cereal grain growth, and a range of 16 to 20% for a doubling is typically found.

    Furthermore, I have personally lived in the hardiest of USDA “hardiness zones” – Colorado for the past 20 years and Northern Minnesota for decades before then. Since the PDO turned negative (colder), ie generally after the “2006,” Colorado has been hardier than in the 1990s and early 00s.

    As for the claim of “an unusual rise in day-time and, especially, night-time summer temperatures being seen in crop belts around the world,” I see contradictory data.

    While there is the claim of this effect, when well-controlled for station quality, it disappears.

    Further study is needed. This post is too anecdotal to conclude anything.

  4. sinchiroca Says:

    I wonder if this problem is better characterized as a matter of species migration than outright species loss. If we consider the warming only, then it’s just a matter of the South becoming more tropical. If Florida ends up more like Cuba, or Venezuela, there’s no loss in species diversity, just a change. The same thing goes all the up the continent.

    Of course, I’m leaving out the elephant in the room: desiccation. Reductions in rain will have a far bigger effect than CO2 concentrations.

    • kiwiiano Says:

      One aspect that doesn’t get much mention is that the higher the latitude, the bigger the day/night length variation, unsettling plants that might be ‘migrated’. There’s also the problem that hotter summers may permit semi-tropical plants to grown at temperate latitudes except that they would get knocked out by the inevitable cold snaps or frosts.

      We could of course just wait for a few tens of millennia for natural evolution to take effect.

      Plus, just as climate change is portrayed as a giant jig-saw puzzle with no edges and no guide picture, the big picture of life on life-boat Earth has a few curly ones awaiting us. Dealing with rising temps & oceans, droughts & floods, will be concurrent with depleted resources, destruction of forest and oceanic biosystems, loss of cheap energy, mass famine migration, breakdown of trade & financial systems.

      Or not….someone please shoot me down in flames, please.

  5. sailrick Says:

    Studies have also shown that increasing CO2 leads to less nutrition (protein) in crops.
    I think Orson is in denial. Climate change will effect agriculture in numerous negative ways, that offset any gain from increased CO2. More frequent and larger floods, droughts, sea water incursion near coastlines, too much heat, loss of irrigation water as glaciers and snow packs decrease – can all be expected.

  6. indulisb Says:

    More CO2 not only reduces protein, but in some crops increases cyanide levels. A double whammy- as protein intake goes down, the effect of cyanide on the metabolism of animals also increases. So you have more cyanide and it also has more effect. A not very positive “positive feedback”. I’d also b einterested in Olson’s figures, especially as they relate to actual food value of the higher yield. If the additional weight is “junk food” then who cares if there is an increase!

  7. neilrieck Says:

    If CO2 was plant food then you would expect that higher levels would produce an explosion of plant life to take advantage of it. Higher levels of photosynthesis would produce then produce higher levels of O2 (oxygen). But O2 levels have been falling since measurements began in 1989 so I’m fairly certain that climate deniers are wrong once again.

    Now my own research is a little more negative. We all know that CO2 is producing higher temperatures due to the green house effect. Photosynthesis is a chemical process which operates best (on average) at 76F (24.4 C) then drops by 10% for every degree F increase. For C3 plants photosynthesis stops at 86 F (30 C).

    Therefore, higher temperatures mean less food. Many publications indicate that human population will continue to grow to 8 or 9 billion but I’m fairly certain we can barely support 7 billion (we’ll cross this level on Oct 31 2011)

    • greenman3610 Says:

      not only that, but if plants are sucking up all this CO2, why do levels continue to rise?

    • sinchiroca Says:

      I have a problem with the assertion that “For C3 plants photosynthesis stops at 86 F (30 C)”. I don’t know what the adjective ‘C3’ means, but I think we should not forget that the highest foliage densities are in the tropical zones, with temperatures regularly in the 90s. I suspect that your source is in some fashion restricted to a particular type of plant — houseplants, perhaps.

      • greenman3610 Says:

        Beware the deadly “common sense gut reaction”.
        wiki is your friend.

        “Plants that survive solely on C3 fixation (C3 plants) tend to thrive in areas where sunlight intensity is moderate, temperatures are moderate, carbon dioxide concentrations are around 200 ppm or higher, and ground water is plentiful. The C3 plants, originating during Mesozoic and Paleozoic eras, predate the C4 plants and still represent approximately 95% of Earth’s plant biomass. C3 plants lose 97% of the water taken up through their roots to transpiration.[1] Examples include rice and barley.
        C3 plants cannot grow in hot areas because RuBisCO incorporates more oxygen into RuBP as temperatures increase.”

        • sinchiroca Says:

          Wow! OK, so the luxuriance of tropical vegetation is due primarily to the supply of rain, not the temperature. Learn something new every day.

          This suggests that agricultural productivity will fall dramatically in those temperate regions where rainfall decreases.

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