So this months (or maybe last) issue of Wired magazine has a great series of articles on the history or apocalyptic predictions and doomsayers. One of the more interesting facets was the timeline of past predictions from supposed experts on the overpopulation of Earth and our inability to grow/harvest food to support the populace.
From lack of technology, deforestation, water shortages and extinction of domesticated meat and over fishing the seas… the predictions go back hundreds of years to as recently as a few decades.
While they have all been proven inaccurate and theories debunked… I think we can all agree that their IS A LIMIT to the amount of people this planet can support; be it 10,50 or 500 billion. The question is, what is that number?
What do you think? What is maximum capacity of our planet before we see REAL worldwide extinction type impacts?
What’s your definition of a REAL worldwide extinction impact? Aren’t we in an era of extinction, as it were?
Certainly there is a limit, but it’s a function of technology. How many people could we cram, Matrix-style, into a one-mile thick shell around the surface of the earth?
I guess what I might be getting at is that if we are elbowing other species out of the biosphere, possible ramifications might occur at a steadily increasing pace.
Yeah I thought of this and admit the definition is ambiguous at best. I would guess the definition I personally would use would be when a production cannot sustain the planet meaning that nearly everyone in a first world country would be severely impacted by the shortage.
This would be through a combination of skyrocketing food prices and availability have negative impacts on the economy as a whole. National emergencies, failing policies and hording all in effect.
Still ambiguous I know but I think we will all really know when our society is in peril.
The answer depends on the period; are we talking about maximum capacity for a limited period–say, a few generations or centuries–or ultimate sustainable carrying capacity of the Earth?
Even given the technology of grain cultivation that gave rise to modern high density civilization, the current human population has unambiguously exceeded the natural carrying capacity of the Earth in terms of food production. The Haber–Bosch process, which binds atmospheric nitrogen into ammonia, is used to manufacture the artificial fertilizers that permit the large scale modern agriculture of the Green Revolution. This allows the nitrogen to be metabolically available for building proteins by plants and animals, including ourselves. To give a sense of scale, this process uses approximately 2% of the annual production of natural gas. Without the process of artificial nitrogen fixation, reserves of nutritionally available nitrogen (primarily from manure and guano) would not sustain current levels of agriculture. A similar limitation are naturally occurring phosphates.
Another fundamental limitation are natural sources of potable water. The statistics on water reserves for sustainable are less clear, as agriculture and industrial usage (especially steel and aluminum production, and textile manufacturing) compete for usage of water, and for many of these processes ‘grey’ (fresh non-potable) water would be usable. However, modern agriculture currently uses unsustainable volumes of ‘fossil water’ from underground aquifers well beyond rates of replenishment, and the overuse is actually compacting the aquifers so that they cannot carry the same future capacity. These aquifers are critical to the hydrological cycle which filters and mineralizes the water. The natural carrying capacity depends on how efficiently the water is used and recycled; currently it is mostly treated as a common resource, with the resulting tragic wastage, but efficient use could reduce waste in industrial and agricultural processes by at least half an order of magnitude.
Of course, one can posit some future technology that could replace both of these in a truly sustainable fashion; for instance, methane production from industrial agriculture and waste treatment could recapture nitrogen for use in the Haber–Bosch process without using non-renewable sources, and water can be filtered and cleaned for reuse by reverse osmotic processes. These would allow essentially infinite growth (subject ultimately to fundamental material resources and space for the population to live) but all of this takes more energy and (especially in the case of water) transportation to the user site, which places additional burdens on a fuel economy currently dominated by non-renewable sources.
This also depends on the lifestyle requirements of the population; currently, a small fraction of the world population enjoys the luxuries of urban society essentially without limit, and the rest of the world gets the cast-offs residue and lives in marginal sustainability. If the entire population of the world lived at the same quality of life and attendant wastage as North America and Western Europe (as many developing nations are currently aspiring to do) there would be extreme burdens on current resources, especially agriculture and fossil fuel usage.
For ultimate sustainability without assuming near-magic recycling and energy production technology, a population of somewhat less than one billion people living in modern urban lifestyle is probably a realistic estimate.
The 1 billion estimate is perhaps a little conservative. How many people could our planet really support? We have plenty of carbon, oxygen, hydrogen and nitrogen, and enough of the trace elements so that biomass requirements shouldn’t be a real problem. The real limiting factor is how efficiently we can produce food for human consumption. Producing food requires energy- but how much?
First we could look at the energy requirements of a typical human body. This seems to be about 125 joules per second, or 125 watts. That is the minimum energy requirement of a human body.
The Earth receives 174 petawatts of energy at the upper atmosphere; the albedo of our planet is about 37%, so we don’t want to use more than 63% of that incoming energy or we risk heatiing it up beyond current temperatures.
(174 petawatts x 67%) /125 watts = 932,640,000,000,000.
That is to say, if we could find a way of converting sunlight into human metabolic energy with 100% efficiency, we could support 932 trillion people on Earth without risking overheating.
Obviously that wouldn’t be possible, but I would point out that limiting the world’s population to one billion represents a energy efficiency of about 0.0001 percent. If we could convert sunlight into human metabolic energy with an efficiency of only 1 percent, then, using only the sunlight that falls on our planet, we could support 932 billion people on our world.
That should be;
If we could convert sunlight into human metabolic energy with an efficiency of only 0.1 percent, then, using only the sunlight that falls on our planet, we could support 932 billion people on our world.
Obviously this would mean that the Earth would be converted into a machine dedicated to supporting human biomass, and the existing biosphere would have no way of surviving; but the OP didn’t specify that elephants, tigers and ants need be included in the equation.
I may be misinterpreting your post but I get the sense that you see urbanism as an obstacle to sustainability. Currently some urban lifestyles have a higher consumtion and enviromental impact than some rural lifestyles, but that is caused by the fact that urban areas are much more productive and greater at generating welth. In themself they are more efficient than rural ones in that you get more “quality of life” per “resource spent”.
Urban people in India have a bigger footprint because they have a much higher quality of living than the people in rural areas. But in more developed countries, this does not hold true. Someone living on Manhattan has a much smaller footprint than someone living in the rural midwest, because they have simmilar levels of welfare but Manhattan can sustain it much more efficiently.
The reason I bring this up is because as a (former) politician and city planner, I’ve had to deal with the perception that city life for some reason would be less “enviromentally friendly” than rural life, when the truth is the exact opposite.
In answer to the OP I would say that the Earths capacity for human life is very dependent on how we construct our living enviroments and where we choose to live. If everyone were to live in dense and integrated urban areas where the climate is mild, the capacity would be huge. If everyone instead chose to live in suburban or rural areas, the capacity is much smaller.
Not only does suburban and rural living enviroments require much more energy, especially for transportation, but it also reduces the amount of productive farmlands.
In reality I doubt that overpopulation will ever be a problem, since there is a strong correlation between the amount of education, quality of living and gender equality that a nation achieces, and a drop in birthrates. Many western nations would now be shrinking if it weren’t for immigration from poorer countries.
I agree that urban organization, of certain descriptions, is more efficient than sprawl. But the footprint of Manhattanites is far larger than Manhattan.
But lets assume people in Manhattan eat the same amount of food, water and other goods as anyone else. It takes less energy to deliver that those goods to Manhattan than it does to deliver the same amount of goods to the same number of people spread over a wider area.
Back of the envelope: If the entire land surface of the island of Dominica were built up to accommodate the same urban population density as the city in which I live now, it could house the world’s entire current population.
I am using “urban” as a shorthand for the lifestyle expectation of modern industrial societies as compared to sustainance lifestyles of pre-industrial cultures, not in the planning or societal architecture sense of the term; in other words, a society that subsists largely on industrial scale agriculture, manufacturing, logistics, and waste disposal. There are, of course, significant graduations in just how much waste is endemic in urban (and suburban) developments and signifcant gains can be made in renewability of products and resources such as energy and water. However, the fact remains that there are unavoidable costs in both the distribution of manufactured goods and the inevitable demands on scarce resources. Greater wealth does, of course, allow sufficient leisure to optimize such systems in comparison to inefficient sustainance lifestyles, but that also promotes greater population growth due to allowable population density. There is also the issue that, as urban populations are largely disconnected from the actual production and manufacture of goods, much of the real costs (especially in terms of use of non-sustainable resources) are hidden. For instance, it takes more than 3500 liters of fresh water to produce a pair of Levis jeans. Note that this figure isn’t from some tree-hugging water conservation group; it is from the ICAC, which is very much concerned about resource availability and conservation of resources to support the cotton agricultural and textile industries, and is spending considerable research dollars to develop cotton cultivars and growing methods to increase yield per volume of water consumed.
While it is true that industrial societies tend to have reduced or even negative population growth correlating with increased educational and vocational opportunities (as the opportunity cost of having children increases) but the population of such societies also has a signficantly larger overall footprint, which again, is largely invisible to the population. When you drink a glass of fresh-squeezed orange juice, grown in a Arizona citris grove irrigated with water from the Colorado river, and delivered within a few days from the point of origin to point of use, there is an extensive total footprint of cost and resource usage that is not visible to the consumer or reflected in the actual price (largely due to how water usage is effectively subsidized). And nearly every product that an urban inhabitant consumes or uses every day has the same extensive logistical and resource footprint, which is completely unavoidable regardless of how efficient you make the systems for distribution, waste disposal, and reuse.
Again, the question is whether the o.p. is interested in the maximum carrying capacity for a limited period–for which we can clearly expand almost without limit, albeit with catastrophic consequences once we exceed resource limits–or sustainability for an indefinite period. That the majority of the world population depends on agriculture and manufacture that requires artifical production of basic resources to support argues that, short of positing the technology to generate such resources without limit, there is not only a limit on the size of a populaton for a given “lifestyle footprint”, but that we have exceeded the “natural” capacity of the Earth to provide such resources in a sustainable manner.
If we assume that technology to generate such basic resources will continue to outpace the use of those resources–say, building and refining basic compounds on a molecular level, or extracting resources from extraterrestrial sources, et cetera–then of course there is no practical upper limit. But one has to understand the basic assumption of that premise, to wit, the faith that technology will provide all that we need. There is no natural law that says that this must be so.
This seems to end up in a strange circular argument: Urban areas are efficient, which means they can sustain larger populations, which means they are unsustainable… Several flaws in that reasoning but the most obvious one is about efficiency.
If we agree that in order to achieve maximum sustainability we preferably want our resources to be renewable, and we always want them to be used as efficiently as possible. Urban areas are simply vastly more efficient than suburban or rural ones already, and have an even greater potential for more efficiency moving forward.
And even though urban envrioments can sustain greater populations, they don’t actually produce them. Urbanism leads to increased levels of education and welfare, which leads to lower birth rates. Rural areas produce the population growth, urban areas simply attract them.
This sounds nice, but is in fact kind of misleading. Everyone is disconnected from the actual production and manufacture of almost all goods, no matter where you live. That’s the inevitable result of a complex network economy. Unless you’re completely self reliant this is true for everyone. And I don’t mean the cute self reliance that middle class greenies aspire to, I mean true self reliance. If you produce all your own food, clothing and shelter as well as handle your own medical problems, then you are no longer disconnected from what is now your one-person economy.
The truth is that someone living on a farm in Arizona is as disconnected as someone living in Brooklyn or Mong Kok. Say you grow maize in Arizona. I’m guessing you eat more than maize. I’m also thinking you didn’t build the TV or produce the WWII documentaries you watch on it. You drive a car, wear clothes and use medicin that was all made in urban areas. You know about your microscopic part of the economy, that of maize production, but are disconnected from everyone elses. You have no idea what the life of the factory worker who was part of building your TV is like, he or she has no idea what your life is like. You’re both equally disconnected.
Actually I think it’s more like 6000. And that holds true whether you’re wearing your jeans riding a tractor in a farm field or on the metro in Paris.
And when the orange grower drinks a beer or a glass of wine… Honestly, you keep coming back to how urban consumption would somehow be less sustainable than consumption elsewhere. That is simply not true. If anything, it’s the opposite, since dense urban areas allow for much more efficient distriution.
People having a glass of fresh-squeezed orange juice will simply have less enviromental impact the closer they are to eacother when they’re having their organge juice. If everyone lived in an urban area of Mong Koks density, the whole worlds population would take up about 10% of Swedens area. And I am pretty confident that we would not have to worry about climate change, biological diversity etc because our enviromental impact would only be a fraction of what it is today.
Kurt Vonnegut wrote a short story about this long ago; I think it was published in “Wampeters, Foma, and Granfaloons”. The protagonist was the sole remaining zookeeper, and the day was when the last non-human biomass was scheduled to be terminated in order to reach the planned maximum human population. After all, why keep lions and elephants, if that same energy could go towards human beings?
The limit was based on energy from “insolation”, the amount of sunlight that hits the planet. With fusion, we could go higher. Goodness knows what the limit would be then. Carbon?
I wish I had a cite, but I remember reading that by far, the biggest fuel requirement for food delivery was “the last mile”, or the trip from supermarket to home, which dwarfs the fuel costs even for transcontinentally shipped foods.
I think it might have been in the book, “The Undercover Economist”, which is a great read for anyone looking for a first clue about macroeconomics.
Malthus was the original doomsayer. His arguments were valid, but his facts were wrong or misleading. He asserted that population grows exponentially while development of land for agriculture was increasing linearly. The result would be a large class of people who could barely sustain their lives. This lead to Scrooge’s cry of “Reduce the surplus population!” which was a reflection of a popular (among upper-class) movement in England to disavow charity since it only exacerbated the problem.
What Malthus didn’t take into account was that productivity of arable land grew exponentially, and at an even higher rate than the population growth. We now have more food per capita. This fact is evidenced by the abundance of poor fat people (in developed economies, certainly not everywhere.)
The growth in productivity was due to technology. All scientifically-based doomsayers since then have underestimated the wild-card of technology. In “A Step Farther Out”, Jerry Pournelle gives plenty of examples of this. The work is quite dated now, but probably still worth a read. He basically says that with sufficient energy we can solve any problem – overcome any currently forseeable limits to growth.
At the time I wondered what he’d do with all that excess heat, but no doubt the same solution: with enough energy, we can cool the planet if we need to.
However, I worry about relying too much on the goose that lays the golden eggs. It still behooves us to see problems ahead before they smack us in the face, like anthropogenic climate change.
Yes, that is true. It’s one of the reasons why cities have such a huge sustainability potential, one that can be achieved quite easily if you just work towards two strategic goals simultaneously: Density and diversity.
The most sustainable living enviroments are the city cores that were planned before the invention of cars. Before cars made transportation so inexpensive (or rather, externalised much of the costs) urban living areas were both dense and diverse. This combination minimizes the need for transportation.
All city cores that are planned before the 20:th century have this in common. Housing is integrated with workplaces and commercial areas. This means that you can satisfy almost all your transportation needs by walking. I live on the main street in a 600 year old city, and I can access the whole cities range of functions with a less than 5 minute walk. The only time a car would save me time is if I have to go to the hospital, which used to be centrally located but was relocated to the outskirts of the city in the 80’s according to the functionalist/modernist planning principles that have unfortunately saturated city planning since the 20’s.
Nowadays the more competent city planners work towards sustainabilty through density and diversity when planning new areas, but the big challenge is to create it in the already existing areas that have been built with the oppsite goals. It’s challenging, but not impossible. Basically you have to create structures that support new functions within the existing framework.
Unfortunately the ideology of modernist/functionalist planning is by design very resistant to change. When we planned cities in the pre-industrial era, there was a firm structure that allowed for vast flexibility. But modernist/functionalist planning was aimed towards creating a “finished” and “perfect” structure, one that isn’t ment to change. Whether it is a suburban sprawl or a “project”. The very way that streets and houses were constructed makes the areas inflexible.
Don’t believe we will ever reach maximum habitation of the earth. God will always be there to create catastrophes like war, disease, earthquakes, floods, volcanoes and such to keep the population down. Don’t worry-be happy!
