population max

November 13, 2007 9:18 AM

Does anyone know of a serious attempt to calculate the maximum potential global population (human)?

I assume this would entail a complex computer model that would calculate changes among a large number of interrealted variables.

posted by bluedogg27 to science & nature (14 comments total)

is cannibalism permitted in your model? the limiting factor would be the land area of earth; if cannibalism is prohibited, then you have to allocate more of the land area to food production, otherwise, you can stack 'em deep and eat 'em cheap. when you and i become one flesh, i will be sure to post about it on metafilter afterward.
posted by bruce at 9:45 AM on November 13, 2007 [3 favorites has favorites]

Carrying capacity is the term for that's often used.

A lot of this type of thing (from Malthus to the Club of Rome) focuses more with the implications of population growth.
posted by milkrate at 9:50 AM on November 13, 2007

It's a hard question. A big variable is time, or rather technological advancement. For instance, if not for our recent understanding and manipulation of genetics, then the limit would have been about 10% of the population ago, for the food dimension. And, we never know when breakthroughs come, so for food at least, the limit might be 5 years of growth or 100000 years.
posted by cmiller at 10:02 AM on November 13, 2007

I can tell you how to come up with a theoretical maximum, irrespective of actual considerations: a human being takes, what, about a half-meter on average (note, number made up based on best guess)? The surface area of the globe is 510,065,600 km², including the oceans. Convert to meters, multiply by 2: 1,020,131,200,000 people.
posted by klangklangston at 10:09 AM on November 13, 2007

It's an unanswerable question as you ask it, because there are too many variables. Standard of living is one of the biggest; if the standard of living is a 1700-square-foot house with two cars, and 2500+ calories a day, it will be far lower than if everyone is living in dorms and eating 1500 kcal/day.

Usable resources is another; using coal, oil, and nuclear power, we can sustain human population for a very long time. If we develop the technology to mine the solar system, we could probably do it for millennia.

If we develop workable fusion power, the carrying capacity of the planet will be how many people we can physically pack onto the surface.
posted by Malor at 10:11 AM on November 13, 2007

As milkrate suggests, if you google population carrying capacity you will get plenty of work on this to chew over. Inevitably it's based on a lot of guesswork and assumptions and in my opinion the research is always ideologically driven and so needs to be taken with a grain of salt.

I'd call the question unanswerable: past efforts (as our old pal Malthus, mentioned above) demonstrate that, among other things, a factor you can't realistically account for quantitatively is future technological development.

Plenty of people think we're well past a sustainable population limit and that a massive die-off is inevitable - ethanol skeptic David Pimentel at Cornell is one of them, for example. His work in this field of study is usually labeled "population ecology" which might be another useful term to explore.
posted by nanojath at 10:55 AM on November 13, 2007

Convert to meters, multiply by 2: 1,020,131,200,000 people.

Except that 1 km^2 is 1,000,000 m^2, so your number should be larger by a factor of 1,000.
posted by dixie flatline at 11:01 AM on November 13, 2007

Oh, that's right. Except that I forgot to mention that my assumptions call for everyone to be 1000 bigger in the future.
posted by klangklangston at 11:05 AM on November 13, 2007

(1000 bigger what? Just 1000 bigger.)
posted by klangklangston at 11:05 AM on November 13, 2007

The difficult question: how much space does a human need? This question becomes exponentially more difficult when you consider whole life spans, and the needs associated.

bruce: "when you and i become one flesh, i will be sure to post about it on metafilter afterward."

How in hell will you do that? You'll be dead.
posted by koeselitz at 12:00 PM on November 13, 2007

Your assumptions also don't take into account that you can building upwards, klangklangston. We could stuff bazillions of people into arcologies.

This question is impossible to answer and depends on gobs and gobs of things that we don't have good numbers for.
posted by Justinian at 12:34 PM on November 13, 2007

Allan Rosenfield, the recently-retired dean of the Columbia School of Public Health, studied this question as part of his studies on world populations. In his introductory class he presented the question as a range of possibilities depending on unknowns and choices about resource allocation.

The pessimistic prediction of carrying capacity was about 4.5 billion, meaning we've already far exceeded it and are due for dieback of hundreds of millions of people now living. The median prediction was 12 billion, and the most optimistic prediction was 17 billion. All three models predicted that the peak would have occurred by 2050.
posted by ikkyu2 at 12:59 PM on November 13, 2007

The Club of Rome attempted a serious effort at this, as milkrate pointed out. Their predictions were detailed in a small book, The Limits to Growth, in the 1970's.

They used 1960's computer modeling, and I am sure even a little google work would dig up a similar efforts with more current and refined models.

It is NOT impossible to generate a number for carrying capacity of the planet, but the number you get will be based on your baseline assumptions, and it will vary so widely that it would be ALMOST useless.

Technological innovation has been humanity's savior (sorry jesus), mostly in plant breeding. There are a bunch of metrics that suggest we can very quickly have a major problem on our hands if we encounter unexpected global food production shortfalls.

It could be that technology solves our current problems with food production, energy supply, pollution control/elimination in time to avoid what looks like a certain train wreck, but many of humanity's problems would be a lot more managable if there were fewer of us.

Even equalizing lifestyles for just the people we have now would contribute some sizeable pressures. Imagine if China's population had America's number of cars per household, etc. Multiply that by the thousands of other things that make up a good life in USA and you can see that it's extremely probablematic.

Personally, I'm not optimistic at 6 billion and downright fatalistic at 10-15 billion.
posted by FauxScot at 2:20 PM on November 13, 2007

Imagine if China's population had America's number of cars per household, etc. Multiply that by the thousands of other things that make up a good life in USA and you can see that it's extremely probablematic.

This was brought up in the same class. Every authority on the subject agrees that it can never happen. The 6 billion people now living can never achieve the standard of living that the average US citizen enjoys, because of scarcity of resources. Rosenfield pointed out that technological advances - better living with less resources - will make up some of the shortfall, and the rest of it will be a real shortfall - the entire world is not destined to live as well as the First World does.
posted by ikkyu2 at 3:47 PM on November 19, 2007