Friday, 8 January 2021

Collapse you say? Part 5, Over Population

Geese and Gulls on Lake Huron

Last time I talked about growth, overshoot and dieoff, and promised to continue with a look at human over population in this post. So here we go.

Figure 1: Human Population level and growth rate 1700 CE to 2100 CE (Current Era)

The diagram above is helpful since it charts not just total population (the green areas), but also the yearly rate of growth (the red line). I believe that, by referring to the various sections of this graph, I can make most of the points I want to make here.

Over on the left side you will note this statement, perhaps not readable on your screen, ".04% was the average growth rate between 10,000 BCE and 1700 CE." From some of the reading I have been doing lately it seems that the growth rate for hunter gatherers before 10,000 BCE was similar.

It turns out that humans are like other species—our population grows when there an abundance of food and shrinks when there is a shortage. For typical species, ways of getting more food include expanding their range, successfully competing with other species and evolving to occupy new niches. This sort of change, based on genetic evolution, tends to happen very slowly. But, unlike other species, we have evolved the ability to have a culture, which acts as a medium for change, and language as a way of passing that change on to future generations. During our approximately 2 million years as hunter gatherers we developed many new ways to access more food and get more good out of it. And we spread to all the continents except Antarctica.

I suspect that by about 10,000 years ago we had just about filled up the world, given the amount of food that was available to hunter-gatherers. Only a few islands, mostly in the Pacific, remained to be discovered and settled. It was not too long after that, in various places around the world, that we began to practice agriculture.

It surprises me that the extra food available from even pre-industrial agriculture didn't cause an increase in our growth rate. Apparently it didn't, but it did allow our population to continue growing at about .04% per year, increasing the population density in areas that were suited to agriculture.

In the millennia that followed the invention of agriculture, we went on to develop irrigation, draft animals, animal and plant breeding, using manure and compost to improve fertility and so forth, all of which increased yields and increased the areas where we could practice agriculture, enabling further population growth.

With a growth rate of .04% per year, a population doubles about every 1700 years. This sounds pretty slow, but give it a couple of million years with no interruption and that population will have doubled nearly 1200 times. No, that's not increased by a factor of 1200, but doubled 1200 times. It would only have to double 10 times to increase by a factor of more than 1000, or 30 times to increase by a factor of more than a billion.

The population around 10,000 BCE was only somewhere between a million and 10 million. It is clear that our past population growth was interrupted frequently, when we exceeded the local carrying capacity, when natural disasters reduced that carrying capacity, or perhaps when diseases reduced our fertility rate. For concrete examples, read Chapter 3 of Jared Diamond's Collapse, which details complete dieoffs on Pitcairn and Henderson Islands in the Pacific and a partial dieoff on the neighbouring Mangareva Island.

This is one of the points I want to make—even with only pre-industrial technology and a relatively small growth rate, the eventual result is that we exceed the carrying capacity of the region where we are living and experience dieoff. The only long term solution is to aim for a steady population with no growth. Again, referring to Diamond's Collapse, read Chapter 9 on sustainable societies in the New Guinea highlands, the island of Tikopia and in Japan during the Tokugawa period. It has been done and without modern technology.

But, with those few exceptions, what actually happened is that around 1700 CE our population growth rate began to increase. I am not certain exactly what caused this, but two things happened at around that time that I suspect had something to do with it. First, we started using fossil fuels to industrialize our economies, greatly increasing the per capita amount of energy available, which drove what we think of as "modernization". Second, Europeans expanded into the so-called "empty" continents of the New World (including Australian, Oceania and parts of Africa). For the indigenous peoples this was not a pleasant experience, with a 90% death rate in many areas after the arrival of Europeans. But it did allow the people of Europe to spread out into new areas, accessing new resources and space to grow. And grow we did.

Around 1900 the growth rate started to increase even more and kept it up with only a couple of bumps until 1968.

A number of advances drove this increased rate of growth. Heat engines burning fossil fuels replaced much of the muscle power used in agriculture, and meant that we no longer had to grow food for draft animals. The invention of processes for converting atmospheric nitrogen into ammonia made synthetic nitrogen fertilizers available in large quantities. Before that nitrogen in a form accessible to plants was created only by bacteria and this was a serious limitation on the amount of food that could be grown. And advances in medical care significantly reduced infant and child mortality.

By the 1960's essentially all the land suitable for agriculture was already in use and a food supply problem was looming on the horizon. The green revolution "solved" this problem by developing varieties of the major cereal grains whose yields respond very well to irrigation and fertilization, and by using pesticides to control competition from weeds and crop damage by insects and fungi.

The people responsible for the Green Revolution saw it as a temporary solution that would allow us to get our population growth problem under control without a major dieoff. In the years since then it has actually been used a means to support an ever growing population with little serious thought of getting it under control.

All this leads to another of the points I wanted to make. Looking at the human race's history with food and population growth, a trend starts to become pretty obvious. Again and again we have increased our food supply, which has led to an increase in population, which required an increase in the food supply, which once provided led to a further increase in our population. That population currently (January 2021) stands close to eight billion, and the majority of people still believe that we'll be able to pull more rabbits out of the hat as needed, using technology to feed an ever growing population, into and beyond the foreseeable future.

To me this seems unlikely. We are using ten calories of fossil fuel energy to produce a single calorie of food these days. This includes large amounts of natural gas for the production of synthetic nitrogen fertilizer. The other two primary plant nutrients, potash and phosphorous, are non-renewable mineral resources. And much of the water used for irrigation is pumped from fossil aquifers that are essentially non-renewable. So, modern agriculture is critically dependent on resources which are becoming depleted as we speak, and for which there is no renewable substitute. Further, climate change threatens to put an end to the mild and predictable weather that has made agriculture easier to do for the last few millennia.

The good news is that the growth rate of our population peaked out at 2% per year in 1968, and has been declining since then. But population growth itself, as opposed to the rate of growth, is still a long way from stopping. For a long lived species such as ours there is a big delay built into the process—our population has continued to get bigger and will continue to do so before it finally peaks out. There are a lot of people alive today who have quite a few years left to live, and our population cannot significantly decrease until they have died. And there are a great many women of child bearing age, who could bear more children and increase our growth rate if circumstances encouraged them to do so.

The right-most section of the graph, covering from 2019 to 2100, is seen by many as pointing to a solution.

This solution comes in the form of the "demographic transition", which according to Wikipedia is: "a phenomenon and theory which refers to the historical shift from high birth rates and high infant death rates in societies with minimal technology, education (especially of women) and economic development, to low birth rates and low death rates in societies with advanced technology, education and economic development, as well as the stages between these two scenarios."

This phenomenon is largely due to the affluence made possible by fossil fuels and the fact that in modern, rich societies children are more of a burden than a blessing, encouraging smaller family sizes. The graph's authors make the assumption that affluence will continue to spread to the developing areas of the world and the rate of population growth will continue to drop, causing our population to peak out at almost 11 billion by the turn on the century. While the graph doesn't show it, those who support this optimistic scenario assume that our population will actually decrease and settle out at a more manageable level in the next century. Our population growth rate would have to go below zero to achieve this. Admittedly, in many developed nations it already has done so.

Many people embrace this scenario enthusiastically, assuming it means that "business as usual" can continue on with no problems. It is especially attractive to the rich and powerful, who are looking for a "guarantee" that they won't have to give up their privileges to get us through the problems that lie ahead.

As you can no doubt imagine by now, I am not convinced. The trouble with this graph is that it is based on the assumption that there will always be adequate resources to support the existing population and to continue with the development that drives the demographic transition.

So many of the resources we rely on are non-renewable and are already becoming depleted, but even if we could somehow manage to switch over to renewable resources, things don't look good.

We are at around 165% of carrying capacity with a population of 7.7 billion (in 2019). With 10 billion people and no increase in average levels of consumption, we would be at 214% of carrying capacity in 2100. But in order for the demographic transition to happen in the developing nations, their level of affluence must increase significantly, taking us even further into overshoot. This is a bottleneck that is going to be very difficult to get through. I expect that we will experience a significant dieoff long before 2100. That dieoff will serve to correct our over population and over consumption problems, but it will not be a process that we have any control over, nor any wish to take part in.

Has anyone done a study which took into account resource and pollution limits along with population growth? Well yes, actually, just such a study was done in the early 1970s, and repeated twice since then: The Limits to Growth. This study used a computerized simulation of our world which produced results in its base run (Business as Usual) that have turned out to bepretty accurate.

Figure 2, The Limit to Growth: Business as Usual version

I did a series of posts about The Limits to Growth a few years ago if you want more details without having to read the book. But the main thing to note here is that the population grows until around the middle of this century then decreases dramatically , along with the food supply and our industrial output, with resources becoming depleted and pollution spiking just before population drops off.

Unfortunately, very few people have taken The Limits to Growth seriously. Criticisms generally take the form of, well, if we just do this or that, it will nicely get us around those limits. This makes me think most people stopped reading after the chapter that describe the "Business as Usual" run of the simulation. I say this because the authors anticipated what people would suggest and did many more runs of the simulation that tried those solutions to see if they would help. They did not. What did help was reducing our level of consumption and living within the limits imposed by the planet and its ecosystems. But of course almost no one wants to do that, so we have continued to head deeper into overshoot and closer to dieoff.

To see in more detail how this dieoff may happen, we need to be aware that thus far we have been discussing the situation in global averages. But we live on a large planet, with many different regions that experience change at different rates.

Resource depletion and climate change, the driving forces behind the coming dieoff, are just getting underway in many parts of the world, and it is still easy to ignore their effects. But in others areas—the Middle East, sub-Saharan African and Central America certainly come to mind—they are already disrupting human habitation patterns. The economy suffers first, with volatile energy prices and increases in prices of food and water. Many people are left unemployed and governments are less capable of supporting social safety nets. Agriculture suffers due to some combination of droughts, floods and heat waves. People from farming communities are forced to pack up and move to the cities, where more people looking for jobs and food are not welcome. Civil strife and sometimes outright war ensues and refugees start to stream out of the areas affected. Most of the refugees are absorbed in nearby countries who are not themselves in the best of shape.

In the past when a society collapsed, it's members had little choice but to tough it out with no outside help. Today, in our smaller, more connected world, some help is usually available from outside an area that is experiencing trouble. And it may be possible to move to an area that is not yet affected. That's good, but it also means that trouble in one area is more likely to spread to others in a domino effect. I expect that this will intensify during the coming decades and gradually lead to the almost complete collapse of our industrial civilization.

So, this has been a lot of information. What conclusions do I reach from it?

Is overpopulation the main problem we should be trying to solve? I would say no, but it is certainly part of the problem. Increasing the size of our population makes coping with over consumption harder, and vice versa. The thing to remember about trying to control overpopulation is that, because of the large delay between reducing population growth rates and eventually reducing our population, this project is not likely to bear fruit in time to get us through the bottleneck we face. Unless we tackle consumption at the same time.

As a successful species we have the built in tendency to multiply if resources are available and to expand until we overuse the resources. Can anything be done about this? The demographic transition is tied to affluence in many ways, so it seems likely to make things worse by increasing consumption. Greater awareness of our situation could lead to cultural influences which would make smaller families more desirable in areas where the growth rate is still high. Educating women can do much to help with that, without requiring excessive consumption. Like so many of the problems we face, the solution is probably doable, but not likely to be implemented in a timely fashion for ideological and political reasons.

Reducing the food supply would definitely reduce our population, and this is likely to be what happens in the event of dieoff, whether we want it to or not. But to deliberately quit feeding people should be morally repugnant. Especially if forced on poor people by rich people who are exempt. The term "eco-fascist" has been coined for people who are in favour of this sort of thing.

I am not one of those people, and I should make it clear that I am not blaming the problems I've been talking about here on the poorer and more heavily populated areas of the world. Indeed, the high level of affluence in the developed nations is directly supported by their exploitation of the developing nations. And the ridiculously high level of consumption by the rich everywhere is a major factor in the overshoot that I've been talking about. Ten percent of the population of the world does over 50% of the consumption.

Next time we'll take a closer look at affluence, the "A" term in the I=PAT equation, and the way our world is organized to drive the continued growth of consumption.

Links to the rest of this series of posts, Collapse, you say?


Joe Clarkson said...

It is my understanding that most of the growth in the human population has been since the beginning of the Holocene. Prior to the warm and stable climate that appeared then, the population fluctuated around a fairly constant value, with some bottlenecks during ice ages. I've read that genetic studies have revealed that the population of humans got down to a few thousand breeding pairs at least once.

I read the study you linked to and believe that their assessment starts about the beginning of the Holocene, 13,000 years ago. What is fascinating is the similarity of the growth rates between agrarian populations and HG populations since then. If there was no particular advantage to agriculture in allowing an increase in population, one wonders why agriculture eventually prevailed. It may be that once the world became full, the social organizations that resulted from agriculture enabled agrarian populations to militarily outcompete HG populations who were forced into conflict by having no place to which they could flee.

Your larger point about the low probability we will be able to control our population overshoot is spot on. I also believe that the human population will crash well before the end of this century, which means it will not be from falling birthrates but rather from rapidly rising death rates.

There are many things that could prompt very rapid and large increases in death rates (in addition to the slower certainties, like climate change and resource depletion), which is why we should all be preparing to avoid them as much as possible. I think you have covered them all at one time or another but I'll list the ones I am aware of (in no particular order):

Financial crises resulting in supply chain collapse
Nuclear war
Carrington event (Coronal mass ejection)
Abrupt and dramatic increase in civil disorder and conflict - civil war (local population collapse only)

Of course there are other potential killers out there that we can't do anything about, like an asteroid strike or a nearby supernova, but since nothing can be done, I don't worry about them.

Irv Mills said...

@ Joe Clarkson
Yep, I'm with you on pretty much all of that.
I think the advantage of agriculture was that it allowed our population to continue growing when spreading out further was no longer an easy option. This being because farming can support higher population densities.

Irv Mills said...

@ Joe Clarkson
But of course the thing to remember about farming is that it places a much higher load on the environment--it's footprint may be smaller, but it is much deeper.
You cut down the trees, work up the soil and kill off most of the native species, replacing them with just a few domesticated ones. And it is a challenge to do this in a sustainable way.