Climate change Threatens the Future of World Crop Production

Discussion in 'Earth Science' started by Woody1, Jun 14, 2017.

  1. billvon Valued Senior Member

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    12,676
    >conclusions?

    Most likely outcome? Canadian farmers rejoice. US farmers lose entire crops to heat wave and drought.
     
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  3. sculptor Valued Senior Member

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    How do you know that this is the most likely outcome?

    .......................
    For decades, I was concerned about the drawdown of the ogallala aquifer, and concomitant loss of the high plains crops.

    I think it is still endangered, but peak drawdown seems to have been 11 years ago.
    Hope?
     
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  5. iceaura Valued Senior Member

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    Nice long growing seasons they've been having in California, Colorado, etc. Big crops, for some reason, did not follow. This year looks like a better one: http://www.latimes.com/nation/la-na-colorado-river-20170217-story.html
     
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  7. billvon Valued Senior Member

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    US farmers are already having problems with drought and with dwindling groundwater. Canadian farmers will benefit from warming - for now.
    Given that the aquifer will be empty by 2028 at current drawdown rates, that doesn't seem so hopeful to me. (Before that it will become unusable due to salts and nitrates being concentrated in the aquifer.)
     
  8. iceaura Valued Senior Member

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    23,859
    AGW creates, in the highest probability projections and matching current trends, greater variability in rainfall both where there is more of it and where there is less. The water stress from higher temperatures, meanwhile, (the evapotranspirative deficit, the thing that damages and kills plants https://en.wikipedia.org/wiki/Evapotranspiration ) is increasing throughout, and also varying more widely.

    So the probability is very high - approaching certainty - that a combination of high water need and low water supply will often exist over large areas of the US, sufficient to damage or even kill all current US crop plants. The threat is especially high given greenhouse effects on night temperatures, when most crop plants rely on not facing significant evapotranspirative deficits.
     
  9. karenmansker HSIRI Banned

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    638
    billvon:

    Re: Your last (parenthetic) statement: (Before that (sic, 2018; KSM) it will become unusable due to salts and nitrates being concentrated in the aquifer.) . . . Can you provide a reliable reference/source that support this contention? And just what is proposed to be the source for salts and nitrates (also chemically considered a salt, BTW) being concentrated in the Ogallalah aquifer? . . . fertilizers? . . . . oil field brines? . . . concentrated animal feeding operations (CAFO)? . . . . what?. . . where? What is the proposed mechanism(s) for such concentration? Also can you provide a source for actual numeric data or modelling to support your contention?

    BTW: I have worked quite a bit on projects involving the hydrogeologic characteristics and actual contamination of the Ogallalah, and I have not run across this ontention, except in generalized, broad-brush negative environmental narratives. Thanks for providing some specific references and source referrals.
     
  10. billvon Valued Senior Member

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    12,676
    Sure. Link to the USGS study is here:

    https://pubs.usgs.gov/circ/1337/pdf/C1337.pdf

    Summary on the nitrate/salt problem from the paper:
    =====================
    Irrigation enhances recharge in this semiarid area and has altered the quality of water recharging the aquifer by increasing the transport of agricultural chemicals and natural salt deposits to the water table. Concentrations of dissolved solids, nitrate, pesticides, and other constituents were elevated at the water table, reflecting the change in quality of recharge in areas converted from rangeland to cropland with applied agricultural chemicals.
    ==================
     
  11. karenmansker HSIRI Banned

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    Thanks billvon . . . . I'll have a look!
     
  12. karenmansker HSIRI Banned

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    638
    Billvon: Still reviewing the USGS reference you provided me . On my cursory initial reading, I have not yet found a statement or any investigation data in the referenced (thanks!) USGS Circular article that corroborates your comment (Before that it will become unusable due to salts and nitrates being concentrated in the aquifer.).

    Here are some other interesting excerpt tidbits from that article and a couple of my comments:

    Excerpts:

    1. Estimated transit times of water and chemicals through the unsaturated zone beneath irrigated cropland at the unsaturated-zone study sites are highly variable, ranging from 49 to 373 years (McMahon and others, 2006).

    2. Climate variability (sic, Climate Change?; KSM) that occurs on interannual to multidecadal time scales also has been shown to be an important control on transit times beneath fast paths (Gurdak, Hanson, and others, 2007).

    3. The southern part of the Ogallala Formation has the poorest water quality (fig. 6–1), with elevated concentrations of chloride, fluoride, manganese, dissolved solids, arsenic,
    nitrate, and uranium greater than the MCL or SMCL.

    4. Elevated salinity in irrigation water is greatest in the southern part of the Ogallala Formation, in which 3 percent of samples had dissolved-solids concentrations in excess of
    2,000 mg/L, indicating severe salinity restrictions if the water is used for irrigation.

    KSM Comments:

    1. It is interesting (to me) that atrazine pesticides were detected in some (14%) of the wells sampled. Atrazine was introduced as a (mainly broadleaf) herbicide in ~ 1950. Prior to Atrazine, the herbicide of choice was 2,4-D, used since ~ 1940; no 2,4-D reported in any analyses (albeit, perhaps not analyzed for; unusual since 2,4-D is a recognized agent orange-related carcinogen) which would have travelled via the same paths (slow or fast) as Atrazine.

    2. (See excerpt 3 and 4 above) It is noted (in the USGS article) that salinity, alkaline salts, arsenic, and uranium, etc. are higher in the Southern part of the High Plains (Ogallalah) aquifer than elsewhere. The article did not note that the southern aquifer area is a mostly sem-arid to arid climate and evaporation of 'ponded' surface waters naturally produces highly- alkaline, salty residues in soils - those waters can percolate to shallow groundwater aquifers if there are no intervening confining (low permability; e.g. silts, clays) layers. Note also that naturally-occurring nitrates and arsenic (and also barium!) are (based on many investigations -including my own) are typically elevated in the southwest semi-arid climate. Salinity and oil-field brine salts and metals are also elevated in (all) areas of oil/gas production which can naturally and incidentally, or through human indiscretions, contribute to shallow aquifer contamination.
     
  13. karenmansker HSIRI Banned

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    AND . . . . another VERY major issue with the Ogallalah . . . . . collapse of the aquifer structure . . . . .! Thought you might like to know . . . . .

    When an aquifer forms it is because (among othe things) of the porosity and permeability and an abundance of available interstitial formational groundwater water. That interstitial water (fresh water in the case of the Ogallalah) provides a level of hydrostatic pressure that 'props-up and open' the grain structure of the formation. When interstitial water is removed faster than recharge occurs (as is happening by overpumping the Ogallalah), that removal is pretty much permanent. This is because the grain-supporting formational hydrostatic pressure is reduced and the aquifer then physically collapses under the weight of the aquifer and overlying geologic formations. Once collapsed, no amount of later-introduced recharge water will restore the lost porosity (water-holding capacity) and permeability (water flow/movement capacity) of the aquifer. Porosity and permeability result from of a number of hydrogeologic factors, but hydrostatic pressure is the main one; significant loss of intergranular hydrostatic pressure can severely restrict the productivity of an aquifer.
     
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  14. Write4U Valued Senior Member

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    4,508
    Especially if you add fracking into the equation. I am sure this is one of the reasons why California is switching to solar power energy, instead of drilling more oil wells and compounding the problem.
     
  15. Write4U Valued Senior Member

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    4,508
    Someone mentioned geothermal energy which peaked my interest. Seems that private geothermal wells are available, which provide a circulating loop, pumping heated fluid from above the earth's magma layers into a heat-->energy converter and then loop the cooled fluid back into the substrate. It is a closed system which apparently is completely eco-friendly.

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    Does anyone have any further information on this?
     
    Last edited: Jul 4, 2017
  16. exchemist Valued Senior Member

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    6,135
    My understanding is that domestic installations like this will always rely on a heat pump, since the temperature of the ground at the shallow depth of these installations will always be below that needed for domestic heating. The key thing is to ensure the rate of removal of heat from the ground does not (on average) exceed the heat flux coming up from below as, if it does, you create permafrost and it stops working! So the area over which the heat capture pipes are spread is important.
     
  17. sculptor Valued Senior Member

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    4,345
    I suspect that conflating ground source heat pumps with the greater geothermal is by nature obfuscatory.
    We did some studies of early ground source heat pumps at the design school at SIU and found that they became less efficient over time(years) if only used for heating. Dry ground is an excellent insulator.
    If, however. used for both heating and cooling, then the ground around the pipes was effectively recharged.
    .......................
    caveat: It seems most likely that modern systems are more efficient than the ones we studied.
     
  18. karenmansker HSIRI Banned

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    638
    This just in! . . . . more fodder for the discussion . . . .

    http://dailycaller.com/2017/06/01/seventh-govt-study-says-fracking-isnt-a-threat-to-groundwater/
    SEVENTH Gov’t Study Says Fracking Isn’t A Threat To Groundwater
    Excerpt:
    A government agency has contradicted claims made by environmentalists for the seventh time and found hydraulic fracturing doesn’t pose a grave threat to drinking water.
    The U.S. Geological Survey (USGS) published a study Wednesday that examined 116 water wells across the energy-rich regions of Arkansas, Texas and Louisiana. The study found nine examples of water contamination in the wells, but every case was either naturally occurring or not linked to fracking.
     
  19. billvon Valued Senior Member

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    12,676
    Actually it doesn't say that. It says "Groundwater travel times inferred from the age-data indicate decades or longer may be needed to fully assess the effects of potential subsurface and surface releases of hydrocarbons on the wells." In other words, they cannot conclude whether or not fracking is a threat, and likely will not be able to for decades.

    Did you read the study?
     
  20. karenmansker HSIRI Banned

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    638
    Yes, I read the study. My above post excerpt is a direct cut/paste from the online presentation. So, what I posted (excerpt) is what the article said! You can disagree, I suppose . . . .
     
  21. Write4U Valued Senior Member

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    4,508
    In the mean time we are faced with this current news:
    Yes, that's the way to study the impacts of fracking on THE most important natural resource of all life on earth.

    Why, pray tell, have several states imposed their own stringent regulations on fracking?
     
    Last edited: Jul 5, 2017
  22. Write4U Valued Senior Member

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    4,508
    Isn't that how (eco-friendly) technology is advancing?

    Once we used solar panels to power small calculators. Now the Nation of Germany has set a goal to become almost energy independent from using solar energy by the year 2050.
     
    Last edited: Jul 5, 2017
  23. iceaura Valued Senior Member

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    23,859
    You posted this:
    That is not what the study said.

    If the article said that, that is one more reason to discount articles from that source, and find a better source of articles about such studies.
    Since the article did say that, you now know better than to rely uncritically on that source for articles - in particular, than to quote them on a science forum. Better to read the study for yourself, and not end up endorsing such poor journalism.
     

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