I'm Jonathan Tomkin from the University of Illinois. This is the last lecture for this week. We're going to be summing up how overall vision of some of the important concepts behind sustainability by looking at how earlier thinkers worried about population growth. We'll see that their worries are very similar to the worries of today. This is a diagram of the world's population. This does not appear to be a sustainable growth pattern, it looks near exponential. We'll discuss why this is unsustainable in this lecture. But next week we'll find out if it really is. Global population is seven billion now. Most recent growth rates for world population is about one percent, and if that were to continue that would imply that the global population will double in about 70 years. Imagine 14 billion people by 2080. What would happen if this came to pass? It's a tough question, but luckily for us somebody has already been doing the hard thinking on this 200 years ago. Thomas Malthus thought that this kind of growth was not sustainable, and he wrote down his reasoning in 1798. Many of these concerns are very relevant for today. Let's explore his reasoning. Firstly,he noted that any population growth that was exponential, this means that it doubles in any given period of time. So here on this slide, I have a picture of the world population growth and an example of how an exponential growth might happen, for every additional unit of time the population doubles. So population goes from one to two, it doubles to four, it doubles to eight, and it doubles to 16. That is an exponential pattern of growth. If we have a one percent growth rate, as we see in the world today, this implies that there is an annual doubling every 70 years. So you could imagine for this time amount, that every 70 year step would double the amount of population on the planet. Secondly, he assume that agricultural production was arithmetic, and its growth or geometric is enough. That is it increases with time in a straight line. So as you can see through the starter set, perhaps it starts out at two, and then we add two for every time step, so it goes to two, four, six, eight, 10. That's how much food we can produce per population, if you like. Now, take a minute to think about what would actually happen, if we tried to compare these two curves. You can either imagine by filling in the spaces on this graph, or you can actually pull out a node pattern sketch for yourself. On the x-axis put the time, we're doing steps one, two, three, four and so on. On the y-axis, we have the units of either population, or the amount of food produced. So take a minute to either think about this, or sketch it out before you continue. Your two curves should look something like this, population increases at a greater and greater rate, it's exponential. While food production increases at a constant rate. If one unit of food is needed for one unit of population, what happens after the point where the two curves intersect? Again, I want you to take a minute, and either note down, or just think what would happen to the world population, or the population of the example, after this point of intersection. The system breaks down. Famine, war, or disease have to prevent the population are exceeding the food supply. We can't have more people and there is food to supply their need for. This point of intersection was described by, Thomas Malthus says, the point of crisis and it has since, become known as a Malthusian catastrophe. Note that if the population is on the same curve as the food produced, the world is always balanced on starvation. So this means that for the vast majority of people, life is a battle just to put enough food on the table. This is what concerned Malthus the most. That population growth would inevitably lead to a decrease in living standards. There'll be mass impoverishment, as people scrambled to get enough food to eat. So this is a very pessimistic view of the future. In a Malthusian catastrophe, living standards can never increase in the long run. They are always reduced to subsistence level. Let's change the model a little bit to make it a little bit more consistent, with what I spoke about in the last lecture. Instead of an arithmetic growth level, let's move back to that carrying capacity idea. Remember how the reindeer could only grow past this carrying capacity for a certain amount of time for crashing back to Earth? We'll explore this idea in more detail later, but for now think of it as an idea of how much population could be supported. Usually food is the limit, as in the case of reindeer. Other natural limits could be pollution, energy, water, space to live. In this case, there would be a flat line as shown by the green line in the figure. Now, we reach a point of crisis and population crashes, and this time, we're kept to that straight level that carrying capacity. Note that doubling the food supply, so if we have a new technology, a new green revolution, and new ability to create food, merely delays the inevitable. In the world's case, if we're growing at one percent, per year, if we have a new ability, a new technology, to double the food supply available. All we do is postpone this crash into subsistence misery by 70 years. As you can see in this graph, all we do is delay the inevitable, because we shift up the carrying capacity, we double the carrying capacity of the Earth, but because at current growth rates, we're going to have double the population in 70 years. Then all we've done is bought 70 years more time before we reach this catastrophe point, where we're all on the edge of starvation. This inevitably comes from the exponential growth in population. So if population is always exponential, like in that reindeer case until the crash, then we're always destined to hit this wall of starvation. It's even more depressing, If you think that we've gone beyond the carrying capacity. So for example you might say that modern agriculture is too dependent on fossil fuels, and since fossil fuels will eventually run out, then we're artificially living above our carrying capacity. So we can imagine then, that if we have a population that lives above the carrying capacity, according to the Malthusian model, we are destined for a crash. So in other words, the population will collapse. Of course, a population collapse of a large magnitude would probably collapse society as well. Could civilization survive, if we only had half enough food to go around. There are lots of things that could follow this pattern beyond population. Of course, we might think about mined goods including energy, like fossil fuels, but also essential resources, or some would say well that we're mining top soils in modern agriculture. So you can use this sort of Malthusian model, not just for population but for lots of other potentially unsustainable systems. Now it turns out, that we did not have the sort of collapse that Malthus predicted over the last 200 years. But in defense of Malthus, his model was essentially correct up until the point of time in which he wrote it. This is an image of urban poverty in 18th century Britain. At this point in time, the masses of Britain were very poor. The increases in agricultural productivity seen over the last couple of centuries in Britain, had done very little to alleviate this poverty because population growth had indeed matched this increase in the carrying capacity of the country. In fact, it's been argued that living standards in 18th century Britain, that is for the average person living in the country, were lower than they were for the stone age peoples that they replaced. The stone age peoples were much less numerous. They were far less people, but they actually had more calories, and they had more protein, and they had more meat. So it has been argued that being a median person, that is the middle person in 18th century Britain meant that you had a worse life, than you would if you were a Stone Age hunter and the gatherer. So Malthus's model was a very good description of what had happened, over the past few thousand years in Britain. In fact, the only times that the average Britain was better off, was when there was a catastrophe from other reasons. So for example, when there was the Black Death, about a third of all the people on the island were killed, and this suddenly meant that there was much more land available, and so the demand for labor went up, and at that point in time, the average peasant farmer enjoyed a higher standard of living than they did previously, or afterwards once the population came back up to that carrying capacity level. This is all very consistent with a Malthusian worldview. So we should remember that, when we're thinking about this model. The reason why I bring this up is because otherwise, Malthus made a spectacularly wrong prediction about the future. This is England's population. The blue line represents the population change over time, and the yellow dot is when Malthus published his model. As you can see, what happened directly after Malthus published the model, was that there was an enormous increase in the population of England, the more the population doubled, then doubled once more, and has almost doubled again, in the last 200 years. Not only that, the average Britain is far wealthier today than they were 200 years ago. The Industrial Revolution meant, that the average person in the country has about 15 times as much wealth today as they did 200 years ago, when Malthus wrote his predictions. So rising populations has not led to mass starvation. Not only that, rising populations has not made people poorer. In fact in both of these cases, the reverse has happened. People in Britain are more numerous and wealthier, than they were 200 years ago. People make Malthusian predictions today. This is often called Neo-Malthusian, it's new Malthusian prediction. Recent Neo-Malthusian predictions have been as bad as the predictions made by Malthus 200 years ago. For example, Paul Ehrlich, wrote in 1967 that the battle to feed all of humanity is over in the 1970's and 1980's, hundreds of millions of people will starve to death, in spite of any crash programs embarked upon now. Now, this statement was made in 1967, and I've marked this with a yellow dot on this graph. The blue line is the world population since then, the population has doubled since the prediction was made, as has the world income per person. So people are both wealthier and more numerous than they were when this prediction was made. As you can see the very opposite of what a Malthusian would predict has happened across the world. This thinking may indirectly influence a lot of other sorts of documents we read when we think about sustainability. This is from one of the very early texts that considered sustainability issues, it's for the Agenda 21 document from the Rio Earth Summit. Baye suggested in this document than a less significant changes were made to the world economy and social systems. This was in 1992, we can expect to have the same sorts of issues Baye talked about, perpetuation of disparities between nations, or worsening of poverty, more hunger, ill health, and literacy. Now on all of these measures, the reverse has happened. Globally, there's more wealth, there's less illiteracy, there's better health. So we have to be aware that when we hear about these Malthusian predictions that it is following a model that sometimes works, and sometimes doesn't. Now it is possible that we are living on borrowed time, and that the only reason why these predictions have failed, these more recent predictions, is because they're just a little bit too early. Maybe we're living on unsustainable practices, just like the reindeer were for so many years. Surely there must be some limit to how much population growth we can have. I think that's probably true, but in the next set of lectures, we're going to talk about population growth, and we're going to find out that it's not all doom and gloom. Produced by OCE Atlas Digital Media at the University of Illinois Urbana Champaign.
