Arthur T Knackerbracket has found the following story:
The area of agricultural land that will require irrigation in future could be up to four times larger than currently estimated, a new study has revealed.
Research by the University of Reading, University of Bergen and Princeton University shows the amount of land that will require human intervention to water crops by 2050 has been severely underestimated due to computer models not taking into account many uncertainties, such as population changes and availability of water.
The authors of the study, published in Geophysical Research Letters, argue forecasters and policy-makers need to acknowledge multiple future scenarios in order to be prepared for potential water shortages that would have huge environmental costs.
[...] "If the amount of water needed to grow our food is much larger than calculated, this could put severe pressure on water supplies for agriculture as well as homes. These findings show we need strategies to suit a range of possible scenarios and have plans in place to cope with unexpected water shortages."
[...] The new research suggests that projections of irrigated areas made by the Food and Agriculture Organization of the United Nation and others have always underestimated the amount of irrigation required in future by basing them on other assumptions.
The study highlights that the potential global extension of irrigation might be twice, or in the most extreme scenario, even four times larger than what has been suggested by previous models.
[...] Agricultural land where crops cannot be supported by rainwater alone is often irrigated by channelling water from rivers or springs, sprinkler systems, or by controlled flooding. Increased irrigation in future would mean more water consumption, machinery, energy consumption and fertilisers, and therefore more greenhouse gas emissions.
Journal Reference
A. Puy, S. Lo Piano, A. Saltelli. Current Models Underestimate Future Irrigated Areas, Geophysical Research Letters (DOI: 10.1029/2020GL087360)
(Score: 2, Interesting) by khallow on Wednesday May 06 2020, @03:49AM (26 children)
Global human population has never grown superexponentially. There's an upper bound to how many kids a woman can naturally have over a given period of time. The exponential rate has changed, and one could say that an increasing exponential rate is mildly superexponential, but there has always been an upper bounded to that rate - namely that no matter how many children, women give birth to, they can't physically exceed this rate - which is just a steeper exponential curve. So when your curve is bounded from above by an exponential curve, then it is at best exponential growth as well.
Thus, the high estimates aren't supported by the formulas because the real world relationships can't follow the formulas.
(Score: 4, Informative) by Anonymous Coward on Wednesday May 06 2020, @04:31AM (12 children)
Research does suggest it has grown super-exponentially, but "super-exponentially" is referring to something other than what you must think. It means anything beyond an exponential function. To be specific in this case, they are talking about what are called "double exponentials" but there are other super-exponential functions. The most used are tetration (which is also sometimes referred to as superexponentiation) and other higher-order hyperoperations.
(Score: 1) by khallow on Wednesday May 06 2020, @04:44AM (9 children)
(Score: 2, Informative) by Anonymous Coward on Wednesday May 06 2020, @05:35AM (8 children)
I still don't get your point then. Double exponential functions grow faster than exponential functions or even factorial functions. You can trivially construct an exponential function that will grow faster in the short term to a given double exponential function, but the growth curve of the double exponential function will win eventually (same as can be done with a linear function for a given exponential function). Nor does that doesn't change the fact that the human growth curve has been super-exponential in nature for quite some time until near-modernity.
(Score: 1) by khallow on Wednesday May 06 2020, @12:09PM (7 children)
Assertions don't make it so. It's physically impossible to have superexponential growth in the first place. Even if women bore as many children as possible, it'd probably cap out around one doubling of population every decade or so.
The point is that you can't construct a superexponential function that successfully models global human population growth over long periods of time because it is bounded from above by an exponential function. Further, they model population growth rate as a power of the present population. Any superexponential growth of that particular model (which corresponds to an exponent greater than one) naturally has an infinite singularity in finite time. In other words, it predicts an impossible result in finite time - so their model doesn't make sense in a regime that they claim existed for much of human history.
(Score: 2) by HiThere on Wednesday May 06 2020, @03:13PM (6 children)
The maximal growth rate for humans is faster than you are supposing, but it *is* bounded by an exponential function. I suspect that the maximal growth rate would be one child per woman per 18 months between the ages of, say, 15 and 45. And all children surviving. That's not very realistic, but it is an reasonable upper bound.
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
(Score: 1) by khallow on Wednesday May 06 2020, @03:26PM (3 children)
That time lag is a large part of the reason I asserted doubling was on the order of 10 years. Having children sooner is more important for fast population growth than having more children over a long time span. Ok, I'll download Libre Office to calculate the true exponential rate. Then you will all pay!
(Score: 1) by khallow on Wednesday May 06 2020, @03:47PM (2 children)
(Score: 1) by khallow on Wednesday May 06 2020, @03:56PM
Here's the polynomial I'm presently trying to factor:
x^90-x^60-x^57-x^54-x^51-x^48-x^45-x^42-x^39-x^36-x^33-x^30-x^27-x^24-x^21-x^18-x^15-x^12-x^9-x^6-x^3-1=0
Multiplication by x is a time step of half a year. This corresponds to saying the number of births 45 years in the future is equal to the number of women who were born in the years 0 through 30 in the future, every 3/2 of a year (which is 18 months). Anyway, once I factor the polynomial, I look for the largest root and that's my exponential factor.
I also noticed that this works only if I assume women only give birth to more women.
(Score: 1) by khallow on Wednesday May 06 2020, @04:00PM
2x^90-x^60-x^57-x^54-x^51-x^48-x^45-x^42-x^39-x^36-x^33-x^30-x^27-x^24-x^21-x^18-x^15-x^12-x^9-x^6-x^3-1=0
(Score: 0) by Anonymous Coward on Wednesday May 06 2020, @07:52PM (1 child)
You are both forgetting many important in human populations. First is that humans don't have distinct generations relative to their lifetime. They overlap to the point where a person can be alive and have grandchildren older than their children. Second is that humans have lived longer over time. Each month of life expectancy adds to the total population of that month due to generational overlap and to the mean number of children per generation by extending reproductive age. Third is that child mortality rate is dropping, meaning that more humans as a proportion of their generation are reaching reproductive age.
Those are just the big three factors and their most obvious ways of affecting human population. There are tons of papers, including the two that TFA cites, on this subject and plenty of free resources online at a simple web or literature search. Feel free to look it up yourself. Many go into great detail as to why an exponential function won't work for human population data.
(Score: 1) by khallow on Wednesday May 06 2020, @10:04PM
None of these items are relevant to the population growth extremes we were discussing.
(Score: 2) by FatPhil on Wednesday May 06 2020, @10:51PM (1 child)
Anyway, attempting to curve fit human population growth onto a simple curve is a fool's errand. There are different phases caused by different environmental factors such as mastery of fire, mastery of communication, mastery of energy sources, and eventually resource shortages, that drive the population on quite unrelated trajectories. It makes sense to curve fit piecewise, with each section having a simpler curve that has parameters which have real world analogues (such that a multiplier would correlate directly to a children-per-household figure, say).
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
(Score: 0) by Anonymous Coward on Thursday May 07 2020, @01:06AM
No, an exponential function with a big enough exponent wouldn't be super-exponential for the same reason that exponential functions aren't linear. They not only are in different forms, but the resulting functions have different properties.
(Score: 5, Funny) by driverless on Wednesday May 06 2020, @04:58AM (4 children)
You didn't read the title carefully enough, they're discussing irrigatation, for which their assumptions are accurate. If it was irrigation then that's another story.
For those who don't know, irrigatation is the feeling you get when your boss comes up to you and begins a sentence with "Mmmmm, I'm going to have to ask you to ...".
(Score: 2) by RS3 on Wednesday May 06 2020, @01:11PM (3 children)
That was supposed to be funny, right? If so, I got it, but many here often don't grasp the subtle humor (which seems obvious to me).
(Score: 2) by driverless on Wednesday May 06 2020, @01:24PM (2 children)
I was wondering how it could possibly be rated "Informative" when it's a bunch of tongue-in-cheek nonsense...
(Score: 1) by khallow on Wednesday May 06 2020, @01:45PM
(Score: 2) by RS3 on Wednesday May 06 2020, @04:26PM
Seemed obvious. I've been modded "troll" for similar humor. (Personally I think the mod system is badly broken.) I was going to mod it "funny" but I wanted to be sure. Someone did, so all is well in Soylentry.
And thanks for the laugh!
(Score: 2) by DeathMonkey on Wednesday May 06 2020, @04:42PM (7 children)
Goddamn, before you start your armchair anti-sciencing could you at least learn what the terms you are using MEAN first?
Superexponential Growth (J-curves) [foresightguide.com]
(Score: 1) by khallow on Wednesday May 06 2020, @09:45PM (1 child)
(Score: 3, Insightful) by FatPhil on Wednesday May 06 2020, @11:10PM
However, with my novelty "Maths Professor" hat on, yup, you're right for a couple of reasons. It's possible to create a J-curve with superexponential features (e.g. abstract/imaginary things like equities/bitcoin value), but (a) it's not asymptotically superexponential (insert huge duhhhh!!!! here); and (b) it's just as possible, in particular when dealing with models of real world material things (e.g. virons, babbies) to create J-curves that never have anything growing faster than normal exponential features. That "4U" institute looks like little more than a diploma mill, I'd be willing to bet it uses things like stock markets for its examples of such curves. If they've chosen curves best analysed as piecewise functions (split at the catastrophe), and then not analysed historical human population as a piecewise function, that would be disingenuous.
Human need not apply. Sorry, I meant superexponential curves do not apply to humans.
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
(Score: 2, Informative) by Anonymous Coward on Thursday May 07 2020, @12:52AM (4 children)
Here [rpi.edu] is a link that better explanation. But basically, the growth is super exponential because the exponential growth is also exponential. But don't expect them to change their mind or admit it if they do.
(Score: 2) by RS3 on Thursday May 07 2020, @02:42AM (2 children)
Are you an RPI student?
(Score: 0) by Anonymous Coward on Thursday May 07 2020, @03:26AM (1 child)
No, but their different colleges have put up a number of courses online over the years that I have used for other things. They are well-regarded, so I figured something from there would be taken more seriously than DeathMonkey's link.
(Score: 2) by RS3 on Thursday May 07 2020, @06:21PM
Thank you for that. My dad went to RPI and I've always found them to produce amazing people and research.
(Score: 1) by khallow on Thursday May 07 2020, @01:17PM
From the link
Nope. And of course, we're in a period of slowing doubling rates, presently at 60+ years. Finally, there's a slide where they fit linear curves to different parts of a log population graph over time. Piecewise-exponential (particularly when the exponential declines at the end!) is not superexponential unless the exponential growth is unbounded.
(Score: 5, Interesting) by bradley13 on Wednesday May 06 2020, @05:53AM (5 children)
There are all sorts of areas in TFA that deserve discussion, but at the root it's about water. Having grown up in the US Southwest, I have rather strong opinions about the water situation: it's a mess. For historical reasons, namely, the fact that water used to be "free" and people claimed rights over the free stuff and retain those rights today, even though they are no longer appropriate. So you have some agricultural concerns growing rice, or almonds, or other insanely water-intensive crops in the desert. Meanwhile, you have other people who can't get enough water to do perfectly sensible things.
The solution is actually quite simple: de-regulate water. Annul water rights and simply declare that water belongs to the person whose land it falls on (precipitation). Let capitalism work: let the price float to where it should naturally be. Want to pump water out of a river? You owe money to the people upstream. If water actually costs money, California's vast almond groves will die - as they should: water intensive crops do not belong in the desert. Huge golf courses in Arizona will turn brown - because you can't afford to water huge golf courses don't belong in the desert. People will actually want low-flow showers and toilets, because water will be expensive.
Meanwhile, in areas with plenty of water, such as the Pacific Northwest, water will be cheap, agriculture will be easy. As it should be, because water is plentiful. Or maybe they'll make a buck by shipping their water to the desert - which is also fine.
What shouldn't exist is the current system, where people with old water rights waste the stuff, and do, because they can't even re-sell the water at anything like its real value.
Everyone is somebody else's weirdo.
(Score: 5, Interesting) by Thexalon on Wednesday May 06 2020, @05:14PM (4 children)
Since I live right by what is easily the nation's largest supply of fresh water, the Great Lakes, I have a very different perspective.
The main reason I can't walk from Ohio to Ontario directly is because of the Great Lakes Compact, a bi-national and multi-state/province government body that has consistently gone to bat to ensure that water isn't removed from the lake basin in the face of numerous proposals to do exactly that. Without it, proposed schemes to supply the southwest of the US and California with water pumped from the Great Lakes would in relatively short order pump the whole area nearly dry. How do I know this? Because that's exactly what happened to the Colorado River: A century ago, there was so much water flowing in it that both the government and industry thought there was no possible way that we'd ever run out, and now the river doesn't even reach the ocean.
How exactly do you intend to enforce that without government action? Also, what about situations where the area upstream isn't populated - is the human who happens to live up in the Sierras now suddenly a water baron making gajillions and deciding which farms will fail as everyone in the Central Valley fights over who is getting enough water?
Also, is it fair for the apartment-dweller who uses a few gallons a day for a shower, a few toilet flushes, and cleaning is competing for that water with farmers who are using it to water crops that should never have been grown in a desert? Wouldn't some tiered pricing make sense so a Walmart shelf-stocker isn't paying the same price for water as someone who recently decided to grow almonds?
I agree that there's lots of bad decisions going on in the southwest around water supplies: There should be no golf courses in Arizona. The increase in nut farming in places that can't grow trees without massive water imports is insanity. I'm not convinced that unfettered capitalism solves your problem.
The only thing that stops a bad guy with a compiler is a good guy with a compiler.
(Score: 1) by khallow on Wednesday May 06 2020, @09:59PM (2 children)
You mean that California interests can't dominate local interests? Who knew that would happen. There's a reason that California was able to get the water from the sparsely populated Colorado River and completely failed to get water from a bunch of other places (Great Lakes, Pacific Northwest, and Yukon/Alaska). Because there's enough people there to resist their interests and the impracticality of the water delivery systems (the one feeding [wikipedia.org] from the Yukon would require 6 nuclear plants just to pump water - similar power would be required for Great Lakes schemes).
It's not some magic governmental body that prevents LA from walking over the rest of North America, but the fact that there's a lot of people who would be effected, if LA tried anything. LA just doesn't have the political power to make such megaprojects possible.
(Score: 2) by Thexalon on Thursday May 07 2020, @01:07PM (1 child)
A few years ago, a municipality nearby to but not quite in the Great Lakes watershed wanted to use Great Lakes water for their municipal water supply, because their current one was drying up. However, the main reason their current supply was drying up was a bottled water plant had been expanding substantially over the last few years, selling their city water at huge markups because they'd put it into a bottle. It was the Great Lakes Compact that told them they couldn't do that, and defended that in court, and while that limited that company's profits it also protected the water supplies of millions of people.
Sure, it helps that the Compact and the well-being of the lakes themselves enjoy a great deal of public support. It also helps that there are legally binding agreements and rules so that if one state changes its mind due to, say, large campaign donations from a company expecting to profit substantially from sending that water somewhere else, they still don't get their way. Because, as we both know, just because the vast majority of the public wants something doesn't mean that's what the government actually does.
The only thing that stops a bad guy with a compiler is a good guy with a compiler.
(Score: 1) by khallow on Thursday May 07 2020, @01:40PM
From what? [freshwaterfuture.org] It's not a significant draw of water.
Sorry, I see instead yet another poorly thought-out regulatory body obstructing human progress. It's one thing to protect against California draining the Great Lakes (which was successfully done long before the Compact was a thing). It's another to protect again a 70k city (Waukesha, Wisconsin) that happens to lie just outside the drainage boundary. Again from the above link, they discussed this second case a little:
Funny how we need all these powerful organizations to stop non-problems.
(Score: 0) by Anonymous Coward on Friday May 08 2020, @05:44PM
Why do several of you guys keep mentioning Arizona? They don't have water problems! Even after drought conditions for 19 straight years!!!!!!!!! And stop mentioning golf courses too. They are totally insignificant compared to the water usage of all the pools in the area, which were only required to have a cover (installed NOT used) about 15 years ago. You hardly ever see a pool covered and they evaporate like CRAZY! Think 1ft of water level in one day during summer months. Also most golf courses used reclaimed water not river/aquifer water. There are quite a number of man-made lakes using reclaimed water too. Fly over Phoenix sometime and try to count how many pools are covered. It's hard to find even a couple among the tens of thousands of pools.
(Score: -1, Troll) by Anonymous Coward on Wednesday May 06 2020, @04:37PM
there's a kind of water right under our feet:
unfortunatly it's black and mixed with carbon.
however it is easy to liberate: just burn it and water, in form of steam is liberated.
also the carbon, a most required building block for all life forms now is available for absorbtion in the surface biosphere ^_^
(Score: -1, Troll) by Anonymous Coward on Wednesday May 06 2020, @05:08PM
Here is a tell for 'garbage news'
in future could be up to
The words 'future' and 'could be'. That means pretty much anything afterwords is usually pure speculation and most of the time total fantasy.
This smells like someone fishing for funding.