Exercises

"Suppose the Whole World..."

by Isaac Asimov    

Suppose the whole world became industrialized and that industry and science worked very carefully and very well. How many people could such a world support?

    Different numbers have been suggested, but the highest figure I have seen is 20 000 000 000. This is ten times the population an agricultural world could support, and a thousand times the population a food-gathering world could support.

Let us suppose 20 000 000 000 is the limit, then. How long would it be before the world contained 20 000 000 000 people?

That depends on how the world's population growth rate rises or falls. The growth rate might slow down or even reverse if there are terrible wars, famines, or epidemics. (Naturally, everyone hopes such disasters won't happen.) On the other hand, the growth rate might rise even further. So far in history, the growth rate has been going up steadily from 0.0007 percent or less before the coming of agriculture to 2.0 percent now. Yet a 2 percent growth rate is not the highest possible. There are nations in the world with a growth rate of 3.5 percent, and with population increasing at this rate it will double in only twenty years.

We can't be sure, then, whether the growth rate will go up or down in the future. Just for the sake of argument, and to keep things simple, let's suppose the growth rate will stay exactly what it is now. If it does, how long will it take the world to increase its population to 20 000 000 000?

If the present world population of 3 800 000 000 doubles, that will make it 7 6000 000 000; and if it doubles again, the population will be 15 200 000 000. Since each doubling, at a growth rate of 2.0 percent, takes thirty-five years, it will take seventy years altogether to reach the 15 200 000 000 mark. Then, fifteen more years will bring the world population to 20 000 000 000. At the present growth rate, in other words, our planet will contain all the people that an industrialized world may be able to support by about 2060 A.D.

Some young people who are alive today may someday have children who will live to see the world of 2060. It may be a world of 20 000 000 000 people, over five times as many as there are today. If this is all an industrial world can support, those people will be living at a starvation level—just barely keeping alive. Surely, that is not a pleasant outlook for a time only eighty-five years from now.

    But wait, perhaps we aren't allowing for changes in the way human beings live.

Let's go back to the food-gathering world. At that time, 20 000 000 would have been the population limit of the world, yet long before that figure was reached, the world stopped being just food gathering. Agriculture was developed, and the population zoomed right past the 20 000 000 mark. In stead of people starving, the average standard of living rose.

The population limit in an agricultural world would have been 2 000 000 000, but long before that figure was reached, the world stopped being just agricultural. The Industrial Revolution took place, and the population zoomed right past the 2 000 000 000 mark. Instead of people starving, again the standard of living rose.

Well, then, is there any reason to be worried now? Before the new 20 000 000 000 mark is reached, might we not expect something else to happen that will make it possible for the population to zoom right past it with the standard of living still rising?

Let's see—

At the time that agriculture was first introduced, the world contained about 1/5 of the people it could hold at most. If agriculture had not been invented, it might have taken perhaps 250 000 years for the food-gathering world to reach its limit.

At the time the Industrial Revolution began, the world contained about 1/2 of the people it could hold at most. If the industrialization of the world had not begun, it would have taken about 250 years for the agricultural world to reach its limit.

Now the world has, perhaps, less than a fifth of the people it could hold, if it is really true that 20 000 000 000 is the industrial limit. Yet the growth rate has grown so high that there is only eighty-five years left for that limit to be reached. In short, every time there is a great change that makes it possible for the world to hold more people, there is less time for that change to happen. and there are far more people to suffer if anything goes wrong.

What's more, each new change comes after a shorter and shorter time. Mankind remained in the food-gathering stage for hundreds of thousands of years before agriculture was introduced. Then mankind stayed in the agricultural age for 10 000 years before industrialization began. But the Industrial Age will have lasted only about 300 years before another great change seems to have become necessary. The next age will then perhaps last only fifty years before still another must come about.

Suppose we decide to hope for the best, however. Let us suppose that a change will take place in the next seventy years and that there will be a new age in which population can continue rising to a far higher level than we think it can now. This means that there will be a new and higher limit, but before that is reached, still another change will take place, and so on. Let's suppose that this sort of thing can just keep on going forever.

Is there any way of setting a limit past which nothing can raise the human population no matter how many changes take place?

Suppose we try to invent a real limit: something so huge that no one can imagine a population rising past it. Suppose we imagine that there are so many men and women and children in the world that altogether they weigh as much as the whole planet does. Surely you can't expect there can be more people than that.

Let us suppose that the average human being weighs sixty kilograms. If that's the case then 100 000 000 000 000 000 000 000 people would weigh as much as the whole Earth does. That number of people is 30 000 000 000 000 times as many people as there are living now.

It may seem to you that the population can go up a long, long time before it reaches the point where there are 30 000 000 000 000 times as many people in the world as there are today. Let's think about that, though. Let us suppose that the population growth rate stays at 2.0 percent so that the number of people in the world continues to double every thirty-five years. How long, then, will it take for the world's population to weigh as much as the entire planet?

    The answer is—not quite 1 600 years. This means that, by 3550 A.D., the human population would weigh as much as the entire Earth. Nor is 1 600 years a long time. It is considerably less time than has passed since the days of Julius Caesar.

Do you suppose that perhaps in the course of the next 1 600 years, it will be possible to colonize the Moon and Mars and the other planets of the solar system? Do you think that we might get many millions of people onto the other worlds in the next 1 600 years and lower the population of the Earth itself?

Even if that were possible, it wouldn't give us much time. If growth rate stays at 2.0 percent, then in a little over 2 200 years, say, 4220 A.D., the human population would weigh as much as the entire solar system, including the sun.

    We couldn't escape to the stars, either. Even if we could reach them, even if we could reach all of them, population would reach a limit. If the growth rate stays at 2.0 percent, then in 4 700 years, by about 6700 A.D., the human population would weigh as much as the entire known universe.

So you see we can't go on forever at the rate we are going. The population rise is going to have to stop somewhere. We just can't keep that 2.0 percent growth rate for thousands of years. We just can't, no matter what we do.

Let's try again, and let's be more reasonable. Suppose we go back to considering the density of population on Earth.

Right now, the average density of population on Earth is 25/km². If the population of the world doubles, then the average density of population also doubles, since the area of the world's surface stays the same. This means at a population growth rate of 2.0 percent per year the average density of population in the world will double every thirty-five years.

In that case, if the growth stays where it is, how long will it take for the average density of population to become 18 600/km²? Such a density is almost 750 times as high as the present density, but it will be reached, at the present growth rate, in just about 340 years. Of course, this density is reached only if human beings are confined to the land surface of the world. Perhaps human beings will learn to live on the bottom of the ocean or on great platforms floating on the sea. There is more than twice as much ocean surface as there is land surface, and that would give more room for people.

That wouldn't do much good, however. At the present growth rate, it would take only forty-five additional years to fill the ocean surface, too. In 385 years, the average density of population would be l8 600/km² over land and sea both. That would be by about 2320 A.D. But a density of 18 600/km² is the average density of population of the island of Manhattan.

Imagine a world in which the average density everywhere—over land and sea alike, everywhere, in Antarctica and Greenland, over the oceans and along the mountains, over the entire face of the globe—was equal to that of Manhattan. There would have to be skyscrapers everywhere. There would be hardly any open space. There would be no room for wilderness, or for any plants and animals except those needed by human beings. Very few people would imagine a world like that could be comfortable, yet at the present growth rate we will reach such a world in only 385 years.

But let's not pick Manhattan. Let's try the Netherlands. It is a pleasant, comfortable nation, with open land and gardens and farms. It has a standard of living that is very high, and yet its average population density is 400/km². How long would it take for our population to increase to the point where the average density of the surface of the world, sea and land, would be 400/km².

The answer is 200 years, by about 2175 A.D.

You see, then, that if you don't want to go past the average population density of the Netherlands, we can't keep our present growth rate going even for hundreds of years, let alone thousands. In fact, we might still be arguing in an unreasonable way. Can we really expect to have a worldwide Netherlands in the next 200 years?

No one really believes that mankind can spread out over the ocean bottom or the ocean top in the next 200 years. It is much more likely that he will stay on land. To be sure, there may be some people who would be living offshore in special structures, on the sea or under it. They would make up only a small fraction of all mankind. Almost everybody will be living on land.

Then, too, not every place on land is desirable. It isn't at all likely that there will be very many people living in Antarctica or in Greenland or in the Sahara Desert or along the Himalaya Mountain range over the next 200 years. There may be some people living there, more people than are living there now, but they will represent only a small fraction of the total population.

In fact, most of the Earth's land surface isn't very suitable for large populations. At the present moment, most of the Earth's population is squeezed into that small portion of Earth's land surface that is not too mountainous, too dry, too hot, too cold, or too generally uncomfortable. In fact, 2/3 of the world's population is to be found on a little over 1/13 of the land surface of the planet. About 2500 000 000 people are living on 11 000 000 square kilometers of land that can best support a high population. The average density on the 11 000 000 square kilometers of the best land is 230/km², while the average density of the rest of the land surface is just under 10/km².

Suppose the population continues to increase at the present growth rate and the distribution remains the same. In that case, after thirty years, the average population density of the less pleasant parts of the earth will reach the 19/km² figure, but the density of the 11 000 000 square kilometers of best land will be 400/km².

In other words, we will reach a kind of worldwide Netherlands density figure, for as far as we can go, in about only thirty years.

    But will all the world be as well-organized and as prosperous as the Netherlands is now? Some of the reasons that the Netherlands is as well off as it is now is that it has a stable government, a highly educated population, and a well-organized industrial system.

This is not true of all nations, and they need not expect to be as well off as the Netherlands when they are as crowded as the Netherlands. Indeed, if they have an agricultural way of life and a poorly educated people, who don't have long traditions of stable government, then a population as dense as that of the Netherlands now is would only bring misery. In other words, the world can't keep going at the present growth rate, even for tens of years, let alone for hundreds or thousands.

The matter of a population limit is not a problem for the future, then. We might as well realize that the world is just about reaching its population limit now.

      (2 369 words)

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