Saturday, July 30, 2011

The relationship between hunger and petroleum consumption-Part 5

Here, I summarize parts 1-4 and put my results into the context of the broader ideas of peak oil, food production and population decline. 

A number of readers may think that it is obvious, or common knowledge, that food production and fossil fuel consumption are directly linked, and therefore, the higher the level of petroleum consumption in the world, in a region, or in a country, the greater the amount of food produced and the less hunger and starvation there will be.  The implications of reaching peak oil and declining along the down side are equally clear—less oil means less food, more hunger, and eventually starvation. 

This was definitely my thinking, until a few months ago when I started to look at the relationship between petroleum consumption and population growth for different regions of the world, and some individual countries, during periods when petroleum consumption dramatically declined.  To my surprise, the population often just kept increasing at the same rate or at most, the rate of increase slowed down a bit.  That is, I saw nothing that one would call a “die off” (see Estimating the End of Global Petroleum Exports; Part 7 and on).

I speculated that the reason why the population didn’t decline was that foreign food-aid has always stepped to substantially prevent what would otherwise be famine and death.   Because of this, I speculated that I needed to use a “softer” indicator of food production than population or population change.

In this series, I used three different “softer” indicators to assess a country's food production system.  That is, the ability of the system to prevent hunger, the percentage of the population with a high BMI and the Food Supply energy.  I looked at how these indicators related to the country’s petroleum consumption rate.  The results of my analysis suggest that regardless of which indicator I considered, a sharp decline in the indicator occurs when per capita consumption rates are less than about 1 barrel per person per year (b/py).   

I think that this could have important implications for which countries or regions of the world will be the first to have problems with food production and starvation, as petroleum production rates go into decline following peak oil.

Summary of Parts 1-4

Figure 8 shows a composite plot of the trend lines of the relationships between per capita petroleum consumption and the three indicators that I studied in Parts 1-4: the global hunger index (GHI, 2010 data); the percentage of the population with a BMI of greater than 25 (%BMI>25); and the available food supply energy (FS; 2007 data).   If you want to see the actually country by country data look at Figure 3, 5 and 6 in Parts 1-4.

The vertical scale represents different units depending on the indicator being considered.  For GHI and %BMI>25 I can use the same index scale and percent scale as reported in Parts1-2 and part 3, respectively.  For FS I converted the food supply energy into a percentage based on the assumption that the trend line values of food supply energy at 0.01 b/py and at 60 b/py corresponded to 0 percent and 100 percent, respectively. 

I think that Figure 8 nicely illustrates that the largest changes in the indicator occur at less than about 1 b/py.  That is, a per capita petroleum consumption rate of about 1 b/py represents an inflection point, below which the food production system, as represented by these indicators, falls apart.

I also looked at three or four subgroups within the data sets for each of these indicators to test whether or not there was an overall significant difference in the mean per capita petroleum consumption rates of the countries within each the subgroups.  A one-way analysis of variance indicated that the capita petroleum consumption rates of the three or four different food supply groups were not all equal (p<0.05). 

I continued the analysis of variance to make multiple group comparisons to see which of the subgroups per capita petroleum consumption rates were significantly different from each other.

Figure 9 summarizes the findings of these tests:

In general, the subgroups of countries with the lower food system indicator (i.e.; alarming or serious GHI; lowest percentage BMI>25; lowest Food Supply energy) have significantly lower mean per capita petroleum consumption rates than the subgroups of countries with the higher food system indicator.  Notice that all of the subgroups with lower food system indicator have mean per capita petroleum consumption rates ranging from about 0.6 to 0.8 b/py.  The subgroups with the second lowest indicator (for GHI and FS) have mean per capita petroleum consumption rates ranging from about 0.9 to 2.4 b/py. 

Finally, for the two indicators GHI and FS, I was able to compare the country-by-country changes in indicator from an earlier date (1990) to a more recent date (2010 for GHI and 2007 for FS) to see if the indicator and per capita petroleum consumption rates changed in a manner that is at least consistent with idea that petroleum consumption is needed for food production.

That is, if the global hunger index increased for a country from 1990 to 2010, did petroleum consumption go down, or, if the global hunger index decreased for a country from 1990 to 2010, did petroleum consumption go up?

Similarly, if the food supply energy for a country decreased from 1990 to 2007, did petroleum consumption go down, or, if the food supply energy for a country increased from 1990 to 2007, did petroleum consumption go up?

The answer to both questions is yes.  I did SIGNS tests for the 99 countries for which I had both GHI and petroleum consumption data in both years, and, for the 124 countries for which I had both FS and petroleum consumption data in both years.  The result of the test indicated that these proposed relationships occurred in more countries than expected by random chance (p<0.01).  That is, the change in global hunger index was inversely related to the change in per capita petroleum consumption rate and the change in food supply energy paralleled the change in change in per capita petroleum consumption rate. 

Conclusions—1 barrel per person per year

So, have I convinced you that about 1 barrel per person per year is a threshold amount of petroleum consumption needed to maintain the food production system?  

Well, I am at least 95% convinced (inside statistical joke) that there are significant difference in the per capita petroleum consumption rates in groups of countries with lower food system indicators versus groups of countries with higher indicator.  Those subgroups with lowest indicator all have mean per capita petroleum consumption rates in the range of 0.6 to 0.8 b/py.  The subgroups with the highest indicators range from 6 to 15 b/py.   This is consistent with the trend lines, which for all three indicators, there is a rapid decrease in the indicator as one transitions from countries with per capita petroleum consumption rates of greater than to less than about 1 b/py.

I am also 99% convinced (another inside statistical joke) that these food system indicators change in a manner that is consistent with petroleum consumption being a necessary ingredient to the food system.  This study doesn’t prove causation, which may be very hard to prove, but it does seem that increased petroleum consumption genrally means increased food production and decreased petroleum consumption generally means decreased food production.

Ho-hum you might say, I knew all of this before.  

Well, to the best of my knowledge no one has ever looked at this before, so I would be interested to know how you knew this.  May be you just assumed that food production and petroleum consumption are linked 1:1, as I once did. 

I think, however, that the relationship is more nuanced than that, and that comes back to my hypothesis that 1 barrel per person per year represents a critical inflection point, below which serious problems with the food production system occur. 

No, I do not see one barrel per person per year as some absolute limit that is written in stone—the data is just too scattered for that kind of conclusion.  

For instance, as illustrated in Figures 3 and 4 of part 2, many countries consuming as low as 1-3 b/py can still have a moderate to low global hunger index, although some other countries can have serious or alarming hunger index values.  Similarly, as illustrated in Figure 6 of part 4, the bulk of countries consuming 1-3 b/py have a Food Supply energy availability of more than 2230 kcal per person per day, although there are a few examples of countries where the Food Supply energy dips as low as 2000 kcal per person per day.

On the other hand, there are no countries that have a per capita consumption of less than 1 b/py and a global hunger index that is anything less than serious, for the two time periods studied.  Likewise, in the two periods studied, only one country with a per capita consumption of less than 1 b/py had a Food Supply energy that was greater than the overall country average Food Supply energy (China in 1990 and Ghana in 2007).

If I have convinced you that a consumption rates 1 b/py is a danger-zone, and you believe that we are at peak oil, then the implications should be clear to you: as petroleum consumption declines below about 1 barrel per person per year in individual countries, or regions, a crisis in food production will spread.  And, it will be the regions with consumption rates declining to the 1 b/py level that will likely have problems with their food system first.

As I already showed in my previous series (see Part 10, Figure 18) Africa is very close to 1 b/py right now, and, Asia-Pacific is not far behind.



  1. World-class analysis again. Thank you.

  2. Good to see that somebody is thinking deeply in this world.

  3. According to Nate Hagens, a human body needs approximately 2000-3000 calories of energy per day body. An average American consumes approx. 230 000 calories per day. Is there a way to tie this angle into your calculations?

  4. Anonymous 3, without knowing the source of Hagens’ comment, my answer is speculative.

    But, it sounds like these numbers are derived from a widely quoted 10:1 to 7:1 ratio of the Total Energy to produce food in the USA to the total food available, per capita. Almost all of these quotes to the ratio relate back to a book by Pimentel published in 1996 and an article by Heller & Keoleian published in 2000.

    Heller & Keoleian’s article, which presented their method in enough detail to actually follow what they did, was discussed in my previous series in Part 9: “Estimating the critical levels of petroleum consumption necessary to sustain the modern food production system” which you can find in this blog.

    The important thing to remember about Heller & Keoleian’s article is that they were trying to look at the TOTAL energy used to produce food, from ALL energy sources, including electricity used in food preparation packaging and cooking (that electricity being produced from nuclear, coal, and natural gas, mostly), plus petroleum used for transportation and agrichemicals, plus natural gas used to produce fertilizer, etc....

    Based on their numbers, in Part 9 of the past series, I estimated that the number of unique BARRELS of petroleum per capita per year used to contribute to this TOTAL energy was about 1.3 to 1.7 b/py.

    This number is in pretty good agreement with the results of the present global study suggesting that 1 b/py is the minimum amount of petroleum consumption to sustain the food production system enough to prevent extensive hunger and starvation.

    I have been considering do a post, or series of posts, to summarize these aspects of Heller & Keoleian’s article in more detial, and maybe try to do an update, but I am not sure if I will do this or not.

    What do you think, is it worth it?

  5. Hi Crash_Watcher,

    Thanks for your reply.

    As the discussion of Heller & Keoleian’s article in part 9 of the previous series is pretty extensive and encompassing, I'm not sure if it's worth it to look into it in more detail.

    Although I have a hunch that by applying your research skills to the same question, you might come up with some other details that would differ from H&K's conclusions and might merit a publication on their own...

    Patrick Whitefield in his Earth Care manual came with a ratio that in ancient China, 1 calorie of work produced around 40 calories of food. I'm unable to say how he got to these numbers, but a preindustrial versus postindustrial comparison might be useful. Or a timeline?

    As for the source of the comments by Hagens, I also can't tell what the source is, but it seems to me that as a general rule of thumb we can say that approx. 10% of the energy consumption in America is food related and the other 90% is everything else.

    Thanks, JK

  6. Hmmm, JK probably you meant 1 kcal of work for 40 cal of food energy? (1 cal in for 40 cal out sounds too good to be true even in China!)

    Anyway, the question of the efficiency of food production over history is an interesting academic question, although I don't really know what data sources would provide this. I think that Pimentel has tried to look at this, if you are looking for a better source.

    The main point, to me, is that the petroleum based food production system, even at 1 b/py, is doomed to end fairly soon. Where it will end first (Africa), second (Asia) etc... likely points to where the food supply problems will develop first.

  7. Hi Crash_Watcher,

    unfortunately I know nothing about the methodology behind Whitefield´s assertion, all I remember is the ratio 40:1.

    Maybe a way to get to the ratio would be to check the total population of a country in ancient times, see what was the proportion of farmers and from calorie needs of the whole population versus the calories expended by doing non fossil fuel augmented labor one could get to something more accurate...? Obviously this is more guesswork than analysis, given the assumptions and missing data.

    Your main point, the fossil fuel based system failing gradually, with the dieoff breaking point being at 1 b/py, is a very interesting one.

    OK, let´s say that with preindustrial methods, agriculture was able to feed 1 bil. people. With the current food production system, we´re able to feed 7 billion.

    If I understand the conclusion of your series correctly, if we keep consuming at 1 b/py, we can keep those 7 bil. people, if we consume less, the best scenario is to fall back to 1 bil.? So 1 b/py is what it takes to keep 6 bil. of people alive?


  8. JK I am going to move and answer your question in the comment section of Part 10, of the previous series, since that is the post that shows the relevant figures, and, my answer may interest the other readers of that post.


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