Two major points:
First, topsoil is being eroded at a significant rate. Cecil commented on this yesterday (http://www.straightdope.com/columns/030620.html), and I have seen similar numbers from many different sources.
Estimates seem to range between 1% and 2% annually.
Second: Topsoil depth is absolutely crucial to being able to grow crops. Average depth right now is right about 11 inches. When you approach 6 inches, yields get abysmal.
So, what does this mean, and should we be worried?
Worried? All we have to do is ignore it and our topsoil problem will go away.
First, topsoil is probably not being eroded at a significant rate in most places. Cecil based his results upon seriously flawed research.
I’ll just quote Lomborg, whom I know you love:
I know you like to dismiss Lomborg out of hand, but I’d appreciate it if you could stick to the facts at hand, rathe than launching into ad hominems.
Estimates in the range of 1% and 2% annually are based on very incomplete data. Other estimates suggest the loss is far less than replacement value. The trouble is that we have few figures and those we do have are contradictory… When the best studies show no signifcant loss at all, we really can’t make such assertions.
Second: Topsoil depth is not, repeat not, absolutely crucial to being able to grow crops. Crops grow with no topsoil at all, repeat, no topsoil at all. Asserting that topsoil is absolutely crucial is simply not true.
Cite!
Is this average a mean, median or modal value? Averaged of what; average per nation, per county, per hectare, per person, per year, per plant? What about the other stats needed to make an average meaningful in this discussion? What is the SD? What is the skew? Average depth where? Over all the world’s surface? All arable land? All cultivated land? All potentially arable and?
Without those figures an average tells us approximately nothing.
What do you mean by average depth now? Is this greater or less than the average depth 20 years ago? How about 200 years ago?
This statement is so broad as to be meaningless. Yield of what, grown where, under what regimen, on what parent material and what solum depth? Yield and topsoil requirements are dependant on soil quality, rainfall, climate, crops, parent material and a whole range of other factors.
For most crops on most soils the assertion is flat out wrong. There are numerous soils where a 6 inch or narrower A horizon produces more than acceptable wheat yields. Far from declining abysmally at less than 6 inches of topsoil, maize yields are only halved when produced in areas with no topsoil whatsoever compared to those produced on over a foot of topsoil. (Thompson, A. L et. al. Topsoil depth, fertility, water management, and weather influences on yield. Soil Science Society Of America Journal 55). Crops like pineapples have even lower topsoil requirements.
I suspect that you are confusing two separate issues. I have seen references to a European report suggesting that in Europe the minimum soil depth for productive yields on unirrigated and unfertilised loam soils is about 15cm. But this has always referred to soil depth, not ‘A ‘horizon depth. I’ve also never seen any clarification on what exactly the figure refers to, but it is obviously fairly atypical. Most wheat for example requires about 5 times that depth of soil…
I will be interested to see you reference for 15cm ‘A’ horizon limits.
It means that your figures are at best dubious and at worst outright incorrect.
We should be worried that we don’t have an accurate assessment of the problem. We should also be worried that people are speaking on this issue from a position of ignorance. That is always a concern.
:eek: A brazen attack on whom many here call the master. Well, cheers to you for having the gumption.
First of all you make no indication of where you got your Lomborg quote. Second the quote doesn’t directly support your assertions.
Lomborg addresses a Pimentel 1974 result and Cecil cites Lester Brown from 1992 and Bruce Sundquist. When was this Lomborg quote written? Was it in a peer reviewed journal?
Cite(s) please.
What crops? Shall we subsist on a diet of pineapples?
A halving of production isn’t abysmal?!!
I wonder how many people couldn’t afford to eat if the price of food only doubled.
Are there any associated costs with growing without topsoil? It seems that an increased use of fertilizers and water would be necessary.
Well, at least you call it a problem. You didn’t seem to show much thoroughness in your rebuttal however. I’m not inclined to trust your judgement yet.
Errata,
Blake got the Lumborg Quote from a book he wrote called “The Skeptical Environmentalist”. Lumborg is purportedly revealing the “bad science” of many environmental researchers. The problem is, while he may have the expertise to point out errors in statistics, he has no where near the expertise required to make the large scale claims he does, primarily that things are getting better.
Article in Scientific American about our buddy Bjorn.
But the single most important factor is that the quote, as you mentioned errata, has nothing to do with Cecil’s cites.
BTW, blake…attacking Cecil with nothing bigger than a discredited statisticians irrelevant quotes may not be the best way to gain credibility on this particular board.
Topsoil Loss: Steep III - Pacific Northwest Conservation Tillage Systems Information Source Looks at global topsoil tonnage and compares it with net loss rates from various factors. End result -2.2%
Crop Yields Decline With Topsoil Loss: Steep III - Pacific Northwest Conservation Tillage Systems Information Source
Oops. bad copy and paste on that topsoil loss link. Here is the correct one: http://home.alltel.net/bsundquist1/se1.html:smack:
Take it to ‘Comment’s on Cecil’s Columns’, where you can join the many other Dopers who are discussing the pros and cons of Cecil’s column.
Because I wasn’t addressing you. If you want to know then just ask.
My word it does. Firstly Lomborg is referring directly to Brown in that passage.
Secondly Cecil refers to Bruce Sundquist’s figures, and Sundquist cites Pimmental as the source of his figures. Sorry I didn’t make that clear.
Lomborg, B., The Skeptical Environmentalist, Cambridge University Press, 1998
What shall we do without strawmen?:rolleyes:
I am addressing the facts presented in the OP. they are wrong. In this particular instance I am addressing the highly erroneous assertion that topsoil depth is crucial to being bale to grow crops. It is not crucial. Important under some conditions, but not crucial.
Beyond that, we could probably try subsisting on, oh I don’t know, corn, or wheat or any other crop at all.
No?!! It isn’t?!! A yield variation of 50% is pretty normal ?!! Far worse occurs as a result of climatic fluctuation?!!
The trouble with abysmal is that it is a subjective and emotive term term. I would like to think that at the very least it means something well below par, rather than simply something that is normal but undesirable.
Also try to understand, a halving does not occur at an approach to 6 inches. The comment I was addressing is that “When you approach 6 inches, yields get abysmal”. A reduction of 50% occurs when there is no topsoil at all. As I pointed out there are numerous soils worldwide that produce normally and sustainably at 6 inches and less
Note that we haven’t actually seen any evidence that most yields become abysmal with an approach to 6 inches. All the actual evidence to date says quite the opposite. This is the point I am addressing. To date it is just a baseless assertion.
I don’t know, but they could sure warm themselves cheaply by burning all these strawmen you keep throwing up.
Who mentioned anything about costs. First we have to see if there is any basis to what ** tastycorn** has clamed before we can start worrying about complex economic arguments.
[quote]
Are there any associated costs with growing without topsoil? It seems that an increased use of fertilizers and water would be necessary.[/quot
If there is, would that make Tastycorn’s assertion that yields become abysmal at an approach to 6 inches any more valid?
**Tastycorn, I could have sworn that I said. Ah yes, I did say ‘I know you like to dismiss Lomborg out of hand, but I’d appreciate it if you could stick to the facts at hand, rathe than launching into ad hominems”.
I see that you totally failed to do this. Instead you have done your usual trick of ad hominem attack on Lomborg, presumably because you are unable to address the isues.
My oath it does. I failed to elucidate and you failed ot follow up Cecil’s sources. Now that we have cleared that up, perhaps you could address the issues raised.
Now on to your source. I don’t know why you referenced it twice:
The Pacific Northwest conservation Tillage handbook.
According to the graph on that page, when topsoil depth approaches 6 inches it is producing at about 60% of maximum yield. That is one crop on one system, and it still only shows a decrease of 40%. Is this what you mean by abbysmal?
The average year to year yield variation for maize in Idaho is 2 tonnes from a maximum of 8 t/ha for irrigated crops. Do you really think that a fall of only 40% is abysmal, when normally you can expect a fall of 25%?
Variation within field trials for wheat commonly run at about 20%, even over very small areas due to minor soil differences. Do you believe that a fall of 40% is abysmal, when 20% can be expected wit only minor differences?
You seem to be implying that your assertion of abysmal yields at an approach to 6inches topsoil is based on one study showing a C40% reduction in single variety of 5 crop species in one location. Is that what you based that blanket assertion on. Is this correct?
Beyond that you haven’t actually answered any questions.
Can we have a reference for your figure of 11 inches average topsoil, and what it means?
How can you say that topsoil is ‘absolutely crucial’ for crop production when crops can still be produced without it?
Can you clarify what you mean by an abysmal fall in yield, including all the associated questions I asked above?
Do you dispute Lomborg’s statements, or are you only capable of meaningless ad hominem attacks?
Tastycorn I’m not sure what that Sunquis refrence is supposed to refer to. If it actually answers any of my questions then can you perhaps provide a quote?
Are you referring to the World at large? Are you talking about wind erosion, water erosion, or crop erosion? Topsoil is easily replaced with crop rotation which addresses all forms of erosion. It may be a problem in 4th world countries who aren’t applying ANY farming practices other than throwing seeds on the ground, but not in the US. Water erosion is the only problem that needs to be addressed and that is more of a polution problem than anything.
And yes, you don’t need any soil to grow sutainable crops. Not that it is needed in the United States, but hydroponic techniques have been well documented and may someday be more viable economically than soil grown crops.
There needs to be a little common sense here, I drive by farms every day and I have friends who farm. Those darn crops keep popping up year after year, century after century.
It’s not an accident that they do. It is a product of science, both in seed technology and farming techniques. it will do nothing but improve as time passes.
It’s really not an issue for me.
This is a public message board and it is good form in GD to indicate where you got your quotes. And I did just ask.
OK I’ll take your word for it since there’s no other indication.
A review of Cecil’s Sundquist link shows a wide variety of sources.
Thank you.
While addressing the author’s credibility does not in itself negate the argument, you have not presented enough for the argument to stand on it’s own. Knowing that this man is publicly ridiculed in one of the most widely distributed and respected scientific journals in the US, and that he claims in his own book not to be an environmental expert, hardly gives me any faith on his assessment of the figures and studies available. Be prepared to make the argument, simply saying, “Lomborg says so” is unconvincing.
So you are contending that any crop will grow fine without topsoil?
Well if one is dealing with 50% loss from climatic conditions another 50% from poor topsoil doesn’t seem very workable.
All of what strawmen? You mentioned one, and that wasn’t even a point in my argument, it was question directed at you.
tastycorn also asked a very important question which I wish to address:“should we be worried?”
Farmers in third world countries cannot afford much fertilizer, so if extensive fertilizer use is necessary then that land is essentially unfarmable. Also many farmers may not have access to extra water that may be necessary to grow under those conditions.
And I did just provide the reference.
Of course I never did this. I will repeat: I’d appreciate it if you could stick to the facts at hand, rather than launching into ad hominems. Do you dispute in any way what Lomborg has said? Do you have any references to refute what he said? If not you are simply engaging in an ad hominem attack.
I am contending what I am contending: that there is no basis for Tastycorn’s assertion that topsoil depth is absolutely crucial for crop production and that your questioning whether we would all have to live on pineapple can be answered in the negative because a range of other crops can be grown with little or no topsoil.
What made you think I was contending otherwise?
I really couldn’t say. Do you have any evidence that this is a legitimate conclusion to draw? Are you perhaps just making an assumption that the two effects can be added together with no evidence at all?
And as I said, we can’t know whether we should be worried until we have some evidence of whether what tastycorn has said is true. To date it appears to be largely a load of old cobblers, hyperbole and exaggeration.
You are arguing about whether we should support the Venusians or the Martians in the interplanetary war. I am asking what bloody interplanetary war.
That aside, if you wish to address his questions then I you should do so. Instead you made the comment about the economic argument in reference to one of my post’s which did not even vaguely relate to economics. That made it either strawman or a non sequitur depending on what you intended to imply. Either way it was invalid and I was right to dismiss it as such.
True. Of course we have yet to see any evidence of the need for extensive fertiliser use. I really have to ask again: what interplanetary war?
Yes, and the Venusians may not be able to breathe in our atmosphere which may be necessary if we ally ourselves to them. I’ll worry about that when I have some evidence of an interplanetary war.
My point is that you haven’t provided or stated Lomborg’s case adequately. There’s nothing to attack yet but his obvious isolation from the scientific community. There were references provided by Cecil’s column at the very beginning of this thread.
In case you didn’t read it here it is. It discusses a variety of sources of topsoil loss and references multiple sources. If the Pimentel data attacked by Lomborg is crucial and all that is needed to refute Sundquist’s assertions, I’d like to see the connection made explicitly.
Now let’s look at some assertions you’ve made:
Which estimates are these and which data is incomplete and why? All you done is make a blanket dismissal.
Lomborg more or less roughly makes this assertion by stating:
“First, they are based on very few and uncertain estimates, primarily stemming form the US.”
This a broad statement which suggests an exhaustive review of the available literature.Yet the mere paragraph you’ve provided is insufficient for making his case. He attacks a couple of studies done by Pimentel and then cites one study in China and Indonesia. Hardly an exhaustive review. You’ve only restated Lomborg’s assertions in more detail without adding proof (if indeed Lomborg is implying conclusions as broad as your previous ones).
Well I was actually just addressing your own assertions. You stated
I assumed that a competent appraisal would account for climatic variances. But it’s hard to say since I don’t have access to your source. If the conclusion of your source was that topsoil depth was indistinguishable from climatic changes, why didn’t you say that?
But if you want some sources here’s one.(warning: PDF)
It claims a clear relationship between soil erosion and crop yeild independent of climatic conditions. It also asserts the that the water storage capacity of the soil is lowered and that when there is little water, the crop loss is increased by lower soil depths. Also at near zero inches 180 lb/acre of fertilizer was required to give a yield near the 12 inch topsoil a horizon.
You haven’t directly addressed Sundquist or Brown’s assertions that tastycorn linked to. You only presented a one paragraph refutation of what might be one of their sources by Lomborg. What reasons do we have to doubt Sundquist and Brown’s assertions?
As I have already said, Sundquist based his assertions on Pimmental’s data;. Pimmental’s data is highly suspect. It’s that simple. If you don’t believe me then look at Sundquists bibliography. There isn’t much more I can do than that.
I shouldn’t really have to repost this should I?
“His estimate of 17 tonne sper hectare for all of Europe has turned out to stem…from a single study of a 0.11 hectare plot of sloping Belgian farmland; the author himself warns against generalisation form this.”
Then you are going to have to go to the source and look at his material aren’t you? You can’t expect me to provide al the literature Lomborg uses to reach his conclusion anymore than I expect you to provide all the literature Sundquist uses to reach his conclusion. That is the point of referencing a source that has an bibliography.
Because it didn’t conclude that. It concluded that maize yields in no topsoil were only halved. That is the only conclusion that I used form it. Anything else is what you has presumed o place on an article you have apparently never read.
Which is not what you were arguing. You suggested that a 50% decrease due to soil loss and a 50% decrease due to water deficit would result in a net 75% loss. Let me quote you:”if one is dealing with 50% loss from climatic conditions another 50% from poor topsoil…”.
The page you reference does not support this assertion. Quite the opposite. It says “when the rainfall was adequate during the growing season there was little difference in yield regardless of A horizon thickness. However in years when rainfall was not adequate there was an extreme difference in yield.”.
In other words there is no decline in crop production provided there is water. When there is a water stress yield declines. It in no way supports your contention that there would be a 50 loss of yield due solely to soil loss and another additive loss due to water stress.
You will have to try again if you want to give any credibility to this point!
However I will thank you for providing the reference, since it also corroborates what I said. The absolute worst case there shows a reduction from 137 Bu/ac to 125 Bu/ac with a reduction in topsoil down to 6 inches. A loss of only 10%. So much for abysmal yields once topsoil drops blow 6 inches
I certainly have. I addressed them by pointing out the flaws in their sources render them unreliable.
As I have already said, Sundquist based his assertions on Pimmental’s data;. Pimmental’s data is highly suspect. It’s that simple. If you don’t believe me then look at Sundquists bibliography. There isn’t much more I can do than that.
I shouldn’t really have to repost this should I?
“His estimate of 17 tonne sper hectare for all of Europe has turned out to stem…from a single study of a 0.11 hectare plot of sloping Belgian farmland; the author himself warns against generalisation form this.”
Then you are going to have to go to the source and look at his material aren’t you? You can’t expect me to provide al the literature Lomborg uses to reach his conclusion anymore than I expect you to provide all the literature Sundquist uses to reach his conclusion. That is the point of referencing a source that has an bibliography.
Because it didn’t conclude that. It concluded that maize yields in no topsoil were only halved. That is the only conclusion that I used form it. Anything else is what you has presumed o place on an article you have apparently never read.
Which is not what you were arguing. You suggested that a 50% decrease due to soil loss and a 50% decrease due to water deficit would result in a net 75% loss. Let me quote you:”if one is dealing with 50% loss from climatic conditions another 50% from poor topsoil…”.
The page you reference does not support this assertion. Quite the opposite. It says “when the rainfall was adequate during the growing season there was little difference in yield regardless of A horizon thickness. However in years when rainfall was not adequate there was an extreme difference in yield.”.
In other words there is no decline in crop production provided there is water. When there is a water stress yield declines. It in no way supports your contention that there would be a 50 loss of yield due solely to soil loss and another 50% additive loss due to water stress.
You will have to try again if you want to give any credibility to this point!
However I will thank you for providing the reference, since it also corroborates what I said. The absolute worst case there shows a reduction from 137 Bu/ac to 125 Bu/ac with a reduction in topsoil down to 6 inches. A loss of only 10%. So much for abysmal yields once topsoil drops blow 6 inches
I certainly have. I addressed them by pointing out the flaws in their sources render them unreliable.
Something tells you didn’t look at his bibliography.There over 700 references. I counted 5 with Pimental’s name. So if less than 1% might be flawed the rest is summarily dismissed? Funny when this sort of approach is taken with Lomborg, you call it “ad hominem”, yet it seems to be your only methodology.
Let’s apply this standard to Lomborg. From the Sci-Am article:
And I should believe anything Lomborg says because why?
Does this have anything to do with the erosion rates in Africa, or salinization, or any of the mulititude of other studies and factors that Sundquist addresses? I fail to see how.
Well if it comes down to a battle of the sources credibility, than I’m going to choose the peer-reviewed journal written by experts in the field, over the non-reviewed book by a person who is admittedly not an expert in what he’s talking about.
If you want the facts to stand on their own, and have us ignore the fact that you’re using a discredited source, then state the facts explicitly. The brief paragraph provided doesn’t even come close to proving what it said.
Are you sure? Couldn’t I have been saying that there was net 100% loss too? In fact my statement was purposely mathematically vague, I wasn’t making a prediction, I was referring to the statistics that were presented by their percentage values and asserting that it seemed like they would compound. And in fact they do.
Umm the beginning of the sentence from my source that you conviently left out said, “One study showed that”. Indicating from the context that this study wasn’t typical yet even then loss due to water shortage was magnified.
The 50% from soil depth figure came from you, are you retracting that estimate now?
From a source which I have shown to be unreliable. So what?
Cite!
Please show us al where you have taken this approach with Lomborg?
Please show us where you have provided evidence that the sources on which Lomborg based his figures are seriously flawed?
Then show me where I said it was an ad hominem that you did so.
You are making this up.
But I didn’t post it in response to those issues.
Then show us the evidence that production decrease form soil loss compounds with production loss form water stress.
So far we have only seen hat production loss from soil loss is only even present under conditions of water stress, not that one gets ‘another 50% from poor topsoil’ as you suggested.
No, it is a reputable published result.
Basically this whole debate comes down to the fact that you cannot dispute Lomborg’s figures or sources except by attacking the author. It also comes down to the fact that there are no reputable figures on soil erosion and no reason to believe that crop yields will decline abysmally even if all the world’s topsoils are reduced down to 6 inches.
I think that unless someone can produce some actual facts then we can leave it at that and consider ignorance to have been fought.
What I just provided for you was testimony that the scientists whom Lomborg referenced felt he was misinterpreting their data. It’s not an attack on his sources it’s an attack from his sources.
In your first post you addressed estimates of 1 to 2% and claimed they were erroneous.
This came directly after your Lomborg quote which you claimed was relevant to discrediting Sundquist and Brown.
This was a worldwide estimate. Not just of Europe and the US. Therefore Africa is relevant. This is topsoil loss comes not just from erosion. Therefore salinization is relevant. Sundquist makes a claim of just under 2%. Here’s a quote from the much mentioned article referenced by Cecil:
I hope you finally realize the depth of information you are trying to cast off without a glance.
I thought you just said you sticking by your claim that the loss was 50% without climatic variance. Make up your mind.
Besides that, the article I provided shows a definite drop in productivity in correlation to soil depth (figure 2 pg2). There is also a distinctly sharper dropoff when the soil is below about 6 inches. Whether or not this is “abysmal” is a point of semantics so far as I’m concerned.
You have not presented any proof that there are no reliable sources on soil erosion. You’ve simply made the assertion and backed it up with a quote from an unreliable source that only makes that assertion and doesn’t prove it.