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Does More Carbon Dioxide Mean Increased Crop Water Productivity? (arstechnica.com)
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.
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.
Correct. Much as higher CO2 levels and temperatures dominated during the Carboniferous period, spurring massive plant growth and laying down many of the geographic strata that turned into the massive coal fields we mine today, we will likely see greatly increased plant growth which is yet another of the negative feedback mechanisms that keeps the global climate catastrophe from happening the way the alarmists want you to believe.
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.
-- "Oh. This guy again."
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.
She was like chocolate when she drank... semi-sweet at first and then increasingly bitter.
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.
C. Sagan : A demon haunted world:
http://www.amazon.com/gp/product/0345409469/
visit randi.org
The difference this time around is that Carboniferous period fungi were unable to break down lignin. Lignin adds rigidity to plant cell walls and was what plants needed to grow into tall trees with the capacity to bind trillions of tonnes of carbon into wood. For about 50 millions years, all the tree trunks that fell over from storms, disease, old age, insects, earthquakes, dinosours knocking them over, what have you, did not rot completely. Much of their carbon was sequestered underground and compressed into coal. The Caboniferous period ended as Fungi evolved the means to digest lignin and ended the massive carbon sequestration.
http://www.mining.com/coal-sto...
So yeah, plant growth will spike, but don't expect that to mean much for reducing global C02 levels.
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...
Increased plant growth does not mean increased yield in food stapple, if we are still limited in Phosporus and nitrogen fixation. But even if it did, the water increase and climate chaotisation would far more offset that. What good is it that Florida could produce more orange, if it loses its coastal city and vast swath of the everglade, or land ? Or if the ocean pH changes destroy the food stapple (fishing) of many countries ? And that is only on top of my head. There are so many factor at play that your typical "AGW is not that bad" is sad.
C. Sagan : A demon haunted world:
http://www.amazon.com/gp/product/0345409469/
visit randi.org
You're also feeding that beef less protein in the same amount of feed.
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...
In short: even if water use efficiency were to increase, that does not result in increased yield, or crop quality.
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.