Guest Post by Willis Eschenbach
Let me start by getting the jargon out of the way. The “NPP” is the “net primary productivity”. It is how many total tonnes of new plant matter are produced around the globe each year as a result of photosynthesis.
In a book excerpt in the February 2002 UnScientific American magazine entitled “The Bottleneck”, Edward O. Wilson, a brilliant ant biologist and also an unrepentant alarmist about, well, everything, put forward the Malthusian argument that humans are about to run out of food. He said that we are currently wedged into a “bottleneck”, he warned of the dangers of “exponential growth” in population, and he averred that we will be squeezed mightily before the population levels off. The following quote was one part of his argument, an idea which has resurfaced recently as a “scientific” claim:
Wilson: “We already appropriate by some means or another 40% of the planet’s organic matter produced by green plants.“
Figure 1. E. O. Wilson. Photo Source: PBS
When I read Wilson’s claim at the time, my mind just went goofy. That was the day I stopped reading UnScientific American magazine. By any reasonable standards, that number is way, way too large. Humans harvesting and consuming forty percent of everything growing? No way. I’ve flown over the expanses of forests of the north and the Amazon in the south, I’ve sailed across endless ocean miles of living green plankton soup, there’s no way we’re consuming forty percent of the new green matter every year, that’s crazy.
So back then, a decade ago now, I decided to follow it up.
I found that in 2002 when Wilson repeated this claim about humans using most of the sun’s energy, it was already very popular. Here’s a few of the many, many references. A 1999 Sierra Club magazine article says “Homo sapiens now consumes [...] 45 percent of the total energy captured from the sun through photosynthesis.”
In “Can America Survive?”, Joseph George Caldwell had the claim as: “Mankind is currently utilizing about half of all the solar energy captured by plant photosynthesis, and even this is not sufficient to cover its food, forest products, and energy consumption.”
Slightly earlier, in 1998 the claim turned in the United Nations “1998 Revision of the World Population Estimates and Projections” as: “Humans use 50% of all of the solar energy captured by photosynthesis.”
I note the different variations on the theme, from “appropriates 40%”, to “consumes 45%”, to “utilizing about half”, to “humans use 50%” … my urban legend alarm is ringing wildly …
I bring this history up because recently, this most tenacious and ludicrous idea turned up once again. This time it appeared in that modern bastion of alarmism, Science magazine.
Figure 2. Steven W. Running. Photo source: Montana Learning
Dr. Steven W. Running wrote a “Perspective” column in Science called “A Measurable Planetary Boundary for the Biosphere” (PDF, paywalled). In that piece, just like E. O. Wilson a decade before, Dr. Running repeats the same specious claim, that humans are
… consuming or directly co-opting 40% of biospheric production;
Running also says:
According to the most recent estimates from global satellite data sets, humans currently appropriate 38% of global NPP.
Now, before I dig further into the origin of this crazy belief, can some one please tell me:
What does it mean to “co-opt” biosphere production?
What does it mean to claim that man “appropriates” 38% of global NPP?
Seriously. What does either of those mean in terms of the NPP? Talk about vague terms, when you use words like that it is just pseudo-scientific babbling, without meaning.
In addition, those are both emotionally loaded words. “Co-opt” means to summarily take or assume for ones own use, with “appropriate” given as a synonym. In turn, “appropriate” means to take without the owner’s permission. Both words have strong negative overtones, and have no place in scientific discourse in my opinion … but more to the point, what do “co-opt” and “appropriate” actually mean regarding human use of the products of photosynthesis?
For example, are the people around Phoenix, Arizona “appropriating” hard-won carrots from their gardens in the desert? No. They are using carrots or eating them or selling them or utilizing them in some definable manner, but they are not “co-opting” or “appropriating” carrots from their own gardens. That’s a very distorted and unscientific description, not to mention unbearably vague. But I digress … where did this crazy belief, this idea that humans consume about half the solar energy captured by photosynthesis, have its origin? Who made this nonsense up in the first place?
Think about it for a minute. There’s no possible way that humans are consuming anywhere near half the green matter produced on the planet every year, that’s impossible by far. When we take a tree we leave the roots behind, the amount of photosynthetically captured energy underground is huge by itself. Where did this mistaken idea get started? And what accounts for the idea’s persistence now that it is started?
I should have guessed.
Because what science doesn’t know, Paul Ehrlich will be very glad to warn you about.
Figure 3. Paul Ehrlich. Photo Source: Stanford
You may remember Paul — in the 60′s, he was writing “The Population Bomb” and warning of widespread starvation coming in the 70′s.
In the 70′s, when the starvation didn’t appear, he was writing of famine and worldwide suffering coming in the 80′s.
And in the 80′s, when there were no worldwide famines, he was earnestly counseling of starvation and widespread suffering coming in the 90′s.
Lather. Rinse. Repeat.
Despite this unblemished record of failed serial doomcasting, Paul is still in business at the same old stand, Stanford University. Tenured professor, doesn’t matter how many mistakes he makes he can’t be fired. He is still making exactly the same prediction, food riots are just around the corner. Well, not quite. You’ll love the logic.
He now is claiming that because his predicted global starvation and food riots haven’t shown up as he confidently had claimed they would …
… that what that proves is when they do show up in the next decade, they’ll be Worse Than We Expected (™ climate science).
I gotta say, it’s almost embarrassing to see a man who has never made a successful prediction in his dotage, scrabbling to explain a lifetime of successive failures … or it would be embarrassing if his ideas had not already caused so much damage.
Not only that, but people are still using his wacky old numbers to predict that death and destruction is just around the corner. The toad at the bottom of the whole pile of “human appropriation” claims, the 1986 treatise which was the genesis and original source of this whole train of bogus “we consume half the sun’s energy” misperceptions, turns out to be called “HUMAN APPROPRIATION OF THE PRODUCTS OF PHOTOSYNTHESIS” by Peter Vitousek, Paul R. Ehrlich, Anne H. Ehrlich and Pamela Matson (1986)
In this paper, they claim that human “appropriation” of the green growing stuff of the planet, depending on whatever they might choose to say “appropriation” means at a given moment, ranges from their low value of 3% to their high value of 40%.
From 3% to 40%??? This is science?
Now to me, that reflects a poorly defined term. If “appropriation” were properly defined, we’d have one number. Instead, they give the Goldilocks estimate, three widely separated numbers. So now we see why they chose such a vague (yet accusatory) word as “appropriating”—so they could handwave about it. On the other hand, their disdain for humans, evident in the emotional loading of their choice of words, is still unexplained … but I digress.
Further reading reveals that at the 3% level, “appropriation” means just what you might expect it to mean — what we actually eat and wear and build our houses with, the stuff we actually use. You know, what is really consumed and utilized by humans, duh. They run through a number of calculations, and they say that the real number for what humans consume is about 3% of the total captured each year by photosynthesis.
As you might imagine, I’ve run the numbers myself, mine are a little higher here and lower there. At the end I get a bit under 2%, they say 3%, but it’s all dependent on assumptions so I’m not going to argue. For purposes of this discussion, we’ll agree with Ehrlich that humans actually use somewhere around three percent of what the sun produces, the NPP.
… 3% …
So I assume that your question, like mine, is … how the heck do you get from 3%, what we actually use, up to 40%, their claimed level of “co-optation”?
In other words, how do they calculate the forty percent when they claim humans have got the insufferable gall to appropriate 40% of the products of solar energy without the owner’s permission?
The secret is that “appropriate” turns out to be what I call an “accordion word”, one that can play any tune and expand to accommodate any definition. If you want to get humans to plead guilty to appropriating excess NPP, three percent just won’t do it at all. You need to expand that, nobody would worry about three percent. You’ve got to jack that number by an order of magnitude and more to get people properly alarmed.
So they just redefine “appropriate”.
You see, at the 40% level, what we “appropriate” means the 3% of the NPP that we actually use and consume each year, the green growing things we eat and wear and build with, plus:
• every green living thing that grows in any human owned pastures and fields, regardless of whether a human ever touches it, plus
• the annual difference in production between what we grow on a piece of land versus their optimistic theoretical calculation of what could have grown on the same land, plus
• the annual production that might have happened where we put our roads and cities (figured, of course, at the highest possible production rates), plus
• estimated maximum production of agricultural lands lying fallow, plus
• if you eat a fish, include all the smaller fish that fish ate, and all the copepods the smaller fish ate, and all the phytoplankton those copepods ate, plus
• the apples that fall off your apple tree and are eaten by the birds, or rot in the soil, plus
• (I kid you not) we get charged for their calculated annual production lost through “desertification”, whatever they choose for that to mean on a given day.
So when you see a deer grazing in a farmer’s back woodlot, the deer’s not really eating that grass, you are—because it’s happening on land someone is utilizing or letting sit fallow, and by the Ehrlichs’ cockamamie calculation that makes it a human “appropriation” of the products of photosynthesis. It’s simple to get up to 40% when you know how …
Why does Steven Running quote this number? For the same reason that E. O. Wilson and Paul Ehrlich quote this number.
The quote it to “prove” how close we are to filling up the Earth, to try to give some mathematical, measurable weight to their crazy, oft-refuted Malthusian fantasies.
Running: “Will human consumption of primary plant production soon reach its limits?”
Wilson: “If humans utilized as food all of the energy captured by plant photosynthesis on land and sea, some 40 trillion watts, the planet could support about 16 billion people.”
C’mon, folks, Wilson is saying that 2.3 times the number of people currently on earth (7 billion) would consume, not just the production of every single green growing thing on the whole planet, but the raw energy captured by photosynthesis to create that production.
This fails the reasonability test, it is wildly out of scale. Does anyone think we currently eat forty percent of everything that the planet grows?
Of course, they are using their 40% “appropriated” figure to make that estimate that the earth could only support 16 billion people. But as their own paper says “We estimate that humans use approximately 7.2 Pg of organic material directly each year—about three percent of the biosphere’s total annual NPP”. That’s their real number, not the 40%.
If we calculate it by their figures, then, they say 3% of the products of photosynthesis are being eaten, worn, or lived in by the 6 billion people on the planet. If we consumed all the products of photosynthesis as he suggests, then we would be able to support an absolute minimum of 6 billion people divided by 3 percent, or 200 billion people.
Or we could calculate it another way. In the Ehrlichs’ paper, they list the total growing matter produced to be 224.5 billion tons per year, (gotta love the “.5″, especially as it is the fourth significant digit on a worldwide guess) which is in general agreement with other estimates of total world production.
For a rule of thumb estimate, we could use the fact that the earth, with 7 billion people, produces about 6 billion metric tons of food and fiber per year (including shells, husks, waste, etc). Conveniently, that means each person consumes a little less than a metric ton of food and waste per year. 225 billion tons of captured photosynthesis would therefore support the food habit of 225 * 7/6 = 260 billion people. Cut it in half to be conservative and allow for use of wood and the like, call it 130 billion people. (Remember, just as Wilson did, I’m just calculating the possible population using NPP alone, and ignoring dealing with the waste streams, overcrowding, and the rest.)
Finally, to calculate more directly the number of people who could be sustained if we could directly eat all the energy captured by plants, we can figure it a third way.
Humans need say 2,500 kcal/day, which very conveniently is about 10 megajoules per day. “40 trillion watts” is what Wilson says is captured by plants, which is 3.5 trillion megajoules per day. Dividing that incoming energy by 10 Mj/day, we find that if we could “utilize as food all of the energy captured by plant photosynthesis” we could feed 350 billion people. Cut that in half for all the uncertainties, call it 175 billion people with room to spare.
Just so we’re clear on this:
Wilson says if humans utilized as food all of the energy captured by plant photosynthesis on land and sea, then the earth could support 16 billion people max.
The true figure (based on NPP alone, just as is his figure) is well over a hundred billion people, depending on your assumptions. I’ve figured the number using three different methods. He’s out by an order of magnitude.
Sadly, this same nonsense is now being peddled in Science magazine by Steven Running. He is once again selling the Ehrlich idea that we’re almost up to the planetary limits, based on the same bogus figures. Here’s Running again:
If global NPP is fixed by planetary constraints, then no substantial increase in plant growth may be possible. Hence, the obvious policy question must be whether the biosphere can support the 40% increase in global population projected for 2050 and beyond.
For this question, it doesn’t matter whether the “global NPP is fixed by planetary constraints”, or is amenable to human expansion as I would argue has already been proven in semi-arid regions around the planet. It doesn’t matter because at 3% actual utilization of NPP, we are so far from running up against constraints based on the NPP we can let our great, great grandchildren worry about it.
Finally, Running makes another misleading claim:
Agriculture now consumes 38% of the global land surface, with major new expansion only available in underdeveloped parts of South America and Africa.
He makes it sound like the world is running out of land to farm. This is not the case at all. In reality, the amount of un-utilized rain-fed cropland is staggering. The unused cropland in Sudan alone, 75 million hectares, is more than enough to feed all of Africa.
There is more unused cropland in Africa (394 Mha) than there is under cultivation in Europe and Russia combined. (314 Mha)
And there is much more unused cropland in South America (413 Mha) than there is land under cultivation in North America (225 Mha).
In addition, there is 117 Mha of unused cropland in North America, and another 150 Mha available in Europe and Russia.
The only area with no available unused cropland is Asia, so they will have to farm smarter rather than more, and may need to import food … which is one reason why the Chinese are so interested in gaining influence in Africa. Details are at the GAEZ website.
The good news is that most of Asia is not using modern farming methods. Average rice yield in North America is 7.9 tonnes/ha … while in Asia overall it’s only 4.5 t/ha, in China it’s 6.7 t/ha, and in India it’s a pathetic 3.5 tonnes/ha. So large increases in productivity are assuredly possible.
And remember, the population is projected to level out somewhere around nine billion people, so we only need ~30% more food production to stay even. A thirty percent increase is easily within reach.
Figure 4. GAEZ study results, suitability for rain-fed crops. SOURCE
So in summary, despite Mr. Running’s best efforts at Malthusian alarmism, he’s come up empty …
• No, we’re not up against planetary limitations, whether based on NPP or on available cropland.
• No, we’re not anywhere near running out of food.
• And no, Paul Ehrlich’s claim that we “appropriate” 40% of the NPP is still not true, no more than when he made it back in 1986.
All the best,
PS – Does this mean that there are no problems, that we can be complacent? No; the steady improvement over the last half century in the nutrition, health, shelter, and clothing of the people of the world has happened precisely because people have not been complacent …