Monday, 19 October 2009

Limits to Growth's version of Dieoff

Debunking the "limits to growth" model of dieoff.

There are five main variables considered in the model (from the early 1970s!). They are:
Population, food production, industrialization, pollution and consumption of non-renewable resources.

Here are the limits:

Nonrenewable resources are assumed to have no possible renewable substitutes and will last 250 years. (A number pulled out of a hat). Further, it is assumed, however, that other non-renewable resources may replace the initial renewable resource. Technology is allowed to raise efficiency of usage by a factor of 4. (So far so good, quibbling about no substitutes for non-renewables by renewables aside, at least the model accepts that efficiency can stretch resources).

The absolute size of the global economy (agricultural and industrial) is assumed to rise linearly. Further it's assumed that raising global pollution 10 times will have a marginal effect on lifetime but raising it 100 times will have a large effect on mortality. (Arbitrary but let's run with it). In addition, it accepts that pollution may be reduced by pollution control technology by a factor of 4. (Again arbitrary but let's run with it).

Agricultural assumptions state more or less that the world cannot feed 20 billion people.
(Again, arbitrary).

Population is assumed to be uncontrollable even with contraceptives, based on the "fact" that the average preferred family size, even for a wealthy and healthy population is 3 children or more always.
(May be based on statistics. I can see flaws but let's run with it.)

With all of these assumptions, we get the population growing to nearly 10 billion by 2060-2070 and then collapsing due to pollution, failure of agriculture and non-renewable resource depletion.

If we take the efficiency combined with pollution control model and assume unlimited resources, the population still crashes, although it gets to nearly 20 billion before doing so, and the economy grows much larger before crashing along with the population.

There are significant flaws with these assumptions.

Population is static or declining in all rich countries with the exception of the United States, which is (barely) above replacement levels. Clearly raising income limits population growth.

Agriculture: There is more than enough to go around even today, but yet, people are starving. Obviously the availability of enough food is not the limiting factor. A realistic assessment shows that incomes are too low. Interestingly it seems that the very poorest countries are the ones with the highest birth rates. Putting these two together, deductive logic shows that raising incomes should therefore limit population. And it does, as is shown by 40 years of data after the model was proposed. In addition, there is significant effort in the non-agricultural area to produce non-conventional food from sources such as algae (which, while not currently affordable for anyone outside the rich world, are in theory, capable of feeding billions of people on non-agricultural land)

Substitutes for non-renewable resources
If we look at the end-use for *necessary* non-renewable resources, they fall under the categories: Heating, Cooking, Fertilizers and Transport.
As JD has shown on his blog (and here too) there are *several* substitutes in all of the areas that do not need non-renewables. In the case of Heating, Cooking and Transport electricity is an adequate substitute. In the case of fertilizer systems changes might be needed at the societal scale for phosphate fertilizer, and nitrogen fertilizer is readily available from electricity and air.

Pollution control.
The assumptions are wildly inaccurate. Pollution can be reduced down to close to zero at considerable expense and reduced to tolerable levels much more inexpensively.

I thus reject the limits to growth model which (like the peak oil dieoff model) is so flawed as to be unusable.


Anonymous said...

You have totally misunderstood the situation of the world. The fact we can think for ourselves doesn't mean we can transcend the laws of a closed system. To much greater beings we must look like a petridish just as we look at a petridish of bacteria and see that their growth must have limits.

Jack Denver

DB said...

Out of the five troll comments posted, yours isn't just a flame so I will respond.

Thank you for pointing out my misunderstanding and then clarifying what you think is my misunderstanding.

You say we can't transcend the laws of a closed system.

What's a closed system?

A closed system has no energy coming in to it.

Is the Earth such a closed system?

It is not.

Anonymous said...

But until we really get into space, which is not looking practical we are essentially a petri dish - there is only so
much space to collect energy from the sun and generate power - there had to be a limit

Jack Denver

DB said...


We are different than a petri dish because we are capable of stopping ourselves from breeding.
Since the original model was created in the early 1970s the average number of children born to each family has plummeted all over the world. There are only a few countries where this is not so.

In addition, though you are correct that there is only so much energy to be collected from the sun, wind, waves, tides et cetera, it's far greater by hundreds of times than what civilization is currently using.
In short the "energy crisis" is an infrastructure problem. More properly it's an engineering problem.


Anonymous said...


While I agree in broad sweep that the model in limits to growth is incorrect, it does not negate the problem of pollution which is very evident from the industrialization of China. There is also the problem of agricultural runoff which is poisoning the oceans.

What is your answer to that?

Alex H

GreenNeck said...


Good to see a cornucopian debunking of TLTG who actually appears to have read the book.

With that said, your main argument seems to be that population growth will stop by itself before we hit some hard limits, as a result of higher incomes. Therefore no growth = no dieoff.

Julian Simon, the patron saint of cornucopians, said that population could grow forever. Do you agree? If not, why not?

DB said...


Thanks for your comment.

It's interesting that you equate growth with population growth.

I tend to agree with this position.

As to whether I believe population can grow forever?

In theory, and I'm about to jump off the edge here, population could grow forever given enough energy.

In practise though, I think we're pretty much limited to the Earth unless we solve our cultural problems and overcome our primate instincts.

That said: how high do I think population can grow?
I think it could conceivably go a lot higher than now, but not with the current distribution of income or infrastructure.

We'd need something like I discussed over on JD's blog: a highly urbanized, highly regimented industrial civilization pulling in a huge amount of energy and with a significant amount of industrially produced food by mechanized means (e.g. the green gloop thing).

Is it practical to think we can get there from here?

I don't know.

If we look at the current level of population, it's very clear that even our current industrial civilization is having a big effect on the environment in terms of simplying the ecosystem.

The question is how much of an effect this is going to have on the human population.

I suspect that in the rich countries the answer is: not much.
They can make up for environmental deficits by artificial industrial means.

In the poorer countries which are hugely overpopulated compared to their capacity to produce or buy food, a massive percentage of the population depends on subsistence agriculture.

Clearly they will be greatly affected if pollution affects the soil ecosystems to such a degree that the soil cannot produce the food they need.

From that perspective there are two ways out:
The All Natural Way, which is that population declines through famine etc or the technological way in which incomes are raised and technical means are found to shore up environmental deficits.

And lastly, do I think population will grow much more?
I think yes and no. Right now we see vindication of both the dieoff crowd and the technical crowd.

In Japan, Europe, ex-warsaw-pact countries and to a lesser extent North America, population growth has effectively stopped and even reversed in some parts, so we are following the technical path to population stabilization.

Elsewhere the answer is not in yet. Population could stabilize by declining birth rates or else it could stabilize by increasing death rates if they fail to raise income enough to be able to produce more food.

I think that about covers my position.


DB said...

Alex H,

Thanks for your comment and your question.

It's true that pollution particularly from the industrialization of China is a problem, and evidence clearly shows this. We have the East Asian brown cloud of pollution, sometimes blocking out sunlight and we have massive gyres of waste hundreds of miles wide of junk floating in the pacific.

Conversely we have a reversal of pollution in North America and Europe to such an extent that salmon are returning to once heavily polluted rivers and the total forest cover is greater now than 100 years ago.

There are significant (but not insurmountable) challenges still ahead.

Historical evidence shows that once a society reaches a particular level of income per head, the spending on environmental control measures rises significantly.

Much of the new pollution is coming from the newly industrialized East and Japan is a good model. Initially Japan was very polluted as China and other East Asian countries are today. As they became more wealthy, they spent on environmental control measures and Japan is similar to Europe and North America.

We need this to happen for China and other rapidly industrializing countries.

Happily we are going to be forced to move world wide to less atmospheric polluting means of transportation because we will shortly have to substitute out declining oil supplies for a combination of natural gas and electricity derived from various sources. Electric transportation is much less polluting than direct fossil fuel powered transportation even if it's powered by coal due to much greater efficiency.

In terms of agricultural runoff, there is clearly a need for a systems change. We are currently putting on much too much fertilizer in order to compensate for the natural fertilizer that exists in soils (symbiotic bacteria, rhizomes, fungi etc) and much of this is ending up in the oceans as you say.

One method may be industrial production of the necessary soil microbes themselves, combined with less intrusive methods of planting. Adding charcoal to the soil seems to help this.

Other methods might be better analysis and precise modeling of how much fertilizer is really needed and have this enforced by the EPA or other equivalent bodies.

Perhaps a technical solution at least in terms of dammed rivers might be some kind of filter to extract phosphates or nitrogen based fertilizers from the flow.

A systems based approach might be to recycle significant amounts of the large phosphate reservoir inside human beings in the form of extraction from the billions of tons of human urine flushed down the toilet every year.

What's missing is a way to monetize these solutions so there is an incentive to implement.


Anonymous said...

More points to consider:

Population increase rates in industrialized countries are decreasing but populations are also ageing. Meanwhile, populations in poor countries are still rising, leading to more human migrations. It's possible that young people from poor countries will have to care for people who grow older in rich ones.

Not all aspects of contemporary middle class lifestyles can be replaced with alternative sources of energy, including aviation fuel, plastics, and various petrochemical products needed for mass agriculture and manufacturing. On top of that, there may also be shortages in minerals (as shown in a *New Scientist* article) and water.

Those latter points put the issue of food into question, especially given high prices due to the price of oil, lack of water, etc.

There's also increasing per capita demand for resources. Right now, two-thirds of human beings live on barely a dollar or two a day, and have been for years, so anyone who thinks that we won't "die horribly" should consider that grim fact. On the other hand, per capita demand is rising (e.g., China's meat consumption was 24 kg per capita per annum twenty years ago; now, it's more than 50 kg) and products demanded, including cars and appliances, require much more resources. If China alone consumed at the same rate per capita as the U.S. (which had around 250 million of 850 million cars worldwide, and for a population that made up only 5 percent of the world), we'd at least another earth. Imagine if more people worldwide became part of the middle class.

DB said...

"Not all aspects of contemporary middle class lifestyles can be replaced with alternative sources of energy, including aviation fuel, plastics, and various petrochemical products needed for mass agriculture and manufacturing."

In fact, aviation fuel can be replaced in limited quantities from bio-fuels and most short hop flights can be replaced by rail or ship.
There have been significant breakthroughs in producing plastics from sustainable biological sources and several uses of plastics can readily be substituted out by renewable or easily accessibly minerals.
In agriculture, nitrogen based fertiliser is often made from natural gas as a feedstock rather than oil, of which we have plenty. In a fallback case, it can be made from air and electricity.

"On top of that, there may also be shortages in minerals (as shown in a *New Scientist* article) and water."
There are significant efforts underway to substitute out fresh water usage for e.g. air in some applications (notably cooling) or else by salt-water or gray-water.
It's a question of cost.
In terms of mineral shortages you're probably referring to e.g. "rare" earths and in particular dysprosium which is "needed" for permanent magnets.
There are lower grade resource available in quantity in Canada, the US and Australia although currently the Saudi Arabia of rare earths is China. In many cases, again, there are substitutes. An example of this is neoprenium, another rare earth, used in the gears for wind turbines. There is work underway to eleminate the gearbox entirely, thus negating the need for neoprenium.

"Those latter points put the issue of food into question, especially given high prices due to the price of oil, lack of water, etc."
As shown, in most cases there are substitutes, which, while being more expensive (currently) than oil based solutions, are nevertheless available.

"If China alone consumed at the same rate per capita as the U.S. "
China will consume *other* products which are substitutes for the products currently consumed in the U.S.
So will the U.S. as the current products become priced out of the market.