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Featured Is Desert Ever a Good Thing?

  1. Sep 20, 2016 #1
    Cutting down rain forest causes desert, and this is viewed as an upset to the world's climate.

    What I'm wondering is whether any and all desert is basically bad, or whether some amount of desert somehow contributes to the health of the planet. In other words, if we exclude the man made deserts from consideration, would the natural deserts that exist be considered to have a positive effect on the earth somehow, or are they, too, symptoms of ill health, so to speak?

    The reason I ask is because you hear about environmentalists trying to protect desert from all kinds of human activities that might upset its balance, but would the whole earth be better off if we were trying to reclaim desert and make it into forest? Do the Sahara and Gobi deserts, for example, perform some important climactic function as is?
     
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  3. Sep 20, 2016 #2

    Bystander

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  4. Sep 20, 2016 #3

    Mark44

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    It takes water to make a forest. If you're going to reclaim a desert, you need to get water to it from somewhere.
     
  5. Sep 20, 2016 #4
    Right, but the question I'm asking is: if we could (get water into the desert) would we just be screwing something up there or elsewhere? Is it even worth bothering trying to come up with a way to do that?
     
  6. Sep 20, 2016 #5

    256bits

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    A desert does not get much precipitation if any.

    Semi-arid would be able to, and does, support grassland - what would be the purpose of changing grassland to forest? The flora and fauna accustomed to the area would be displaced due to human activity.
    Extremely arid is, well, extremely, dry. Transporting water for irrigation to the area could be costly, but due to evaporation the land could actually end up being useless for anything after a few years, as salts are brought up to the surface.
     
  7. Sep 20, 2016 #6

    jim mcnamara

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    For some desert soils the answer is yes. Desert alkali soils have poor water infiltration, so irrigation does not "transform" these environments into productive farmland, grazing land, or lovely parks.

    This link goes on about man-made alkali soils, but they exist naturally as well.
    https://en.wikipedia.org/wiki/Alkali_soil
     
  8. Sep 20, 2016 #7

    fresh_42

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    An example: Beneath the Sahara there are huge aquifers which are currently emptied. Do we achieve something other than consumption and wasted waters? The same is done to the Ogallala aquifer in the US for agriculture purposes, i.e. consumption.
    So we actually had the chances of water in the desert and do not achieve anything from it.

    From the point of view of a wide spread life form on the planet, these all are short handed goals with vast damages to long term success.
     
  9. Sep 20, 2016 #8

    Mark44

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    I don't believe that the problem is so much that salts are brought to the surface, but rather, salts in the water that is transported are left behind after the water has evaporated.
    This has happened in parts of Arizona, such is in the Salt River area near Phoenix, where desert land has been transformed via irrigation. This is documented in the book "Cadillac Desert", by Marc Reisner.

    There is one that is far from empty, the Nubian Sandstone Aquifer System, the largest known fossil aquifer.
     
  10. Sep 20, 2016 #9

    fresh_42

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    "Because of the predominant hyperarid climate there are no renewals to this aquifer system. It's water level sank about 60 m due to massive usage in recent years. Optimistic prognoses suggest that the aquifer will be depleted in 200 years from now, based on current usage."
    [Wikipedia, https://de.wikipedia.org/wiki/Nubischer_Sandstein-Aquifer, translated by me, so forgive me eventual bad wording please.]

    It quotes the science part of a German newspaper. To get an impression what is meant by usage, you may look at the photo of grain growing there: http://www.badische-zeitung.de/bild...er-wueste-traum-fuer-200-jahre--44431478.html

    44431474.jpg
     
  11. Sep 20, 2016 #10

    Mark44

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    Like I said, it's far from empty, with ~200 years worth of water in it. That's a long way from what you said about aquifers being "currently emptied." Were you referring to some other aquifer?
     
  12. Sep 20, 2016 #11

    fresh_42

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    No, I was simply thinking in longer terms than 200 years. I don't think this is a long period for a resource that won't renew itself on a planet that gets continuously warmer *) (which might shorten this period). And of course this figure doesn't take local shortages or national differences into account.

    I don't know the prognoses for the Ogallala and they are certainly more difficult to make, as there is a net draw-off to be calculated.
    However, 17 billion gallons a day (in 2000) is quite a lot.

    Edit: *) with an exponentially growing population to feed
     
  13. Sep 20, 2016 #12

    Mark44

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    It's dangerous to make predictions about anything that far out, and neglecting possible technological solutions. One that comes to mind is desalinization of ocean water, using fission reactors or solar collectors to supply the necessary energy.
     
  14. Sep 20, 2016 #13

    fresh_42

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    Yes, I agree. I'm concerned anyway. To hope for future technologies seems to me to be as comparable dangerous (although I wouldn't have used this word). It's like a gulf course in AZ: can be done, but should it? Or Las Vegas. This city is a contradiction in itself (personal opinion).
    But you are right, as with the necessary pressure, humans are quite inventive.

    The Israelis use a membrane effect on an industrial level, if I remember correctly. I wonder why that isn't used elsewhere.
     
  15. Sep 20, 2016 #14
    However, the charging of aquifers is a geological process and thus making predictions relating to process are quite appropriate over time scales considerably longer than two hundred years. Might we address the provision of water from some other source by technology? Very likely, but it does not alter the assessment of current usage as profligate.
    What I have not yet seen addressed, though I may have missed it, is what does the OP mean by "bad" and "good" and the "health of the planet". Desertification is bad for orchids, but very good for some type of arachnids!
     
  16. Sep 20, 2016 #15
    Not very specific terms but "you know what I mean." Rainforest is cut down in Brazil to plant grass for cattle. Many animals and plants die. Cattle eat for a few years, rancher makes some money, then the land is unusable, rancher moves on, land becomes desert. Could be some spiders now thrive, but the overall result is "bad." Much more life has been wiped out than not.

    The kind of problem I thought might arise if you reforested the Sahara, for example, is some possible screwing up of the worlds wind patterns that could alter the distribution of rains elsewhere one way or another. That sort of thing. I was wondering, for example, if someone might say a certain amount of desert is good because a certain volume of air has to be heated so it will rise and cause winds that have a beneficial global effect. I don't know if that's the case, I'm just throwing out a speculative example of desert having some global benefit I'm not aware of.
     
  17. Sep 20, 2016 #16
    Not bad for those who evolved to live there :)
     
  18. Sep 20, 2016 #17

    PAllen

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    Dessert is psychologically almost always a good thing. Oh, about desert ... actually the same statement - I love hiking in deserts, something about the terrain grabs me (also forests and mountains, as well). So, aesthetically, wide variety of terrain is nice. I would also think that specialized adaptations of life in deserts could prove useful as biotechnology source material or model. Since I don't really know much ecology, I can only give an anthropocentric rationale for preserving deserts.
     
  19. Sep 20, 2016 #18

    anorlunda

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    Every change has some winners and some losers. The winners call it good. The losers call it bad. Some people call all changes bad. Some people call lack of change bad. Our planet is not a democracy where if there are 60/40 losers/winners that the majority rules.

    The question is a value judgement, not a question of science.
     
  20. Sep 20, 2016 #19

    phinds

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    Based on almost total ignorance, I look at it like this: If you look at the Earth as a system, I think natural deserts are just part of the order of things and that asking if they are "good or bad" is trying to apply a man-made standard to a system we didn't create and probably shouldn't mess with (although we do, of course).
     
    Last edited: Sep 20, 2016
  21. Sep 20, 2016 #20
    The health or goodness of any parcel of land must be related to the fitness of the land for a purpose.
    Consider, how would you judge the health of a patch of martian soil? It is pristine, unspoilt, and poisonous.
    ...
    A thought occurred to me. Deserts have a relatively high albedo: https://en.wikipedia.org/wiki/Albedo#Terrestrial_albedo
     
  22. Sep 20, 2016 #21
    Here's where the "you know what I mean" factor should have kicked in. My question is pretty obviously anthropocentric. "Good" and "bad" are human value judgements, so, yes, I'm concerned about the earth as a 'vessel' for human life most of all.

    To the extent we have screwed up the Amazon it's because we sacrificed a long term human benefit for a very short term one. I'm really not concerned about the welfare of monkeys except to the extent a healthy monkey population means a healthy human population, if it does. I would be kind of happy if all bees died out because I don't like being stung, but it turns out bees have a huge benefit to people in that they pollinate the plants we eat.

    So, were we to reforest the Sahara, would we just be doing the same thing somehow? This is where I would assume science has something to say: there must be people who study the effect of desert on the global weather system.

    The question is asked with the assumption humans are to be the ultimate winners, long term.
    This is the kind of thing I'm wondering about. What happens if the earth's albedo comes to be outside certain parameters? You don't have to answer that, I'm just saying it's the sort of thing that would have to be closely looked at before undertaking to reforest some huge desert.
    We're not exactly in a position to not mess with it to some degree if we want to survive: even woods-dwelling tribesmen have to cut trees down and kill animals. The role of science in this is to provide the best information about what alterations to nature we can get away with.
     
  23. Sep 20, 2016 #22
    Given that we're being anthropocentric, here, could the argument be made that we don't know if we've "screwed up" the Amazon yet? What long term human benefit have we sacrificed and what is its value compared to what was gained?

    Incidentally, I found this: https://en.wikipedia.org/wiki/Amazon_rainforest#Sahara_Desert_dust_windblown_to_the_Amazon
    We don't really know the costs or benefits associated with a mega-project like this, but the easiest way to learn is to do it. We should reclaim a large desert for science!
     
  24. Sep 20, 2016 #23

    anorlunda

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    My point was that humans disagree on what win/lose mean. Aren't you assuming the view of a supernatural observer deciding for us?
     
  25. Sep 20, 2016 #24
    It was altered to raise beef for human consumption, but using it for that purpose for a few years screws it up for that purpose forever. The thing that's really crazy to me is that they don't even bother to harvest the wood when they get rid of the forest: they bulldoze it over and burn it.

    Right!!! Let's just do it!!!!
     
  26. Sep 20, 2016 #25
    I don't think humans disagree on what win/lose means. The disagreement is probably over how much we should be concerned with future generations.
     
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