Man lives in balance with other species in a world that has certain limits. In this world, it is impossible to achieve an unchanging, once and for all established ratio - every biological species has periods of growth and decline in population size.
Some species can dominate for a certain time, then others become dominant. If the species are close to each other in their "capabilities", then such "ups and downs" are usually not very significant.
If a predator depends on a certain type of prey, then it cannot eat the entire population, because after that it will be doomed to starvation.
If you depict the changes of two populations graphically, it will be seen that they are constantly changing direction - up and down, as, for example, in this graph:
Figure 2. The Lotka-Voltaire model is used to illustrate the change in the size of the predator and prey population. This chart reflects the situation when these changes are not too significant.
In fact, populations often undergo much more significant changes, as shown in the following example. At the beginning of the study period, the number of baboons is 80 individuals, and the number of cheetahs is 40 individuals:
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If species develop in parallel, then the natural balance between populations remains approximately at the same level. But if predators suddenly find another, better source of food (you can call it a source of energy, since food supplies the body with energy), then the size of the prey population can dramatically increase.
For example, yeast can convert sugar from grape juice into alcohol. The yeast population grows temporarily and then declines as the food source disappears and the fungus dies from alcohol. Or a bacterium can multiply in the human body if it finds the necessary nutrition for itself, and the body's defenses are not working effectively enough.
Often, to illustrate this phenomenon, an example is given with the deer population of St. Matthew's Island, where lichen abundantly grew on the rocks. The expanded population of deer began to eat the lichen at a faster rate than it grew. At some point, the lichen was completely gone, and the deer population curve also fell sharply.
Figure 4. Changes in the number of reindeer herds on St. Matthew's Island, according to a study by David Klein of the University of Alaska
The deer example is similar to the sharp bends in a predator-prey plot. The reindeer ate the renewable food source faster than it could reproduce. There were few other sources of food for animals on the island, so some of them managed to survive, but still the decline in population was very sharp.
Recently, the number of people has changed very significantly:
Figure 5. These changes in human population were taken from the "Atlas of World History" by Makevedi and Jones, 1978
The dramatic increase in numbers coincides with the period of extraction and use of fossil fuels and begins in the early 19th century. However, if we look at an even earlier period of time, we will see that the growth was observed over a very long period. Man learned to use fire over a million years ago. And starting from 75 thousand years BC, the growth of the human population has become quite stable:
Graph 6. Growth of the human population as they master new sources of energy. Horizontally - the number of years to date, vertically - the population size. From left to right: fire control, agriculture, global mining, fossil fuels
The first significant population growth occurred when humans learned to burn biomass and use the resulting fire in order to cook food, warm themselves, improve stone tools and scare away predatory animals.
All this allowed our ancestors to populate new territories of the globe, simultaneously exterminating many species of animals. Biologist and paleontologist Niels Eldridge believes that the first of six periods of mass extermination of animals began when the first people began to spread widely throughout different parts of the world about 100 thousand years ago. The second phase began about 10 thousand years ago, when mankind started farming. Even in these early stages, the energy used by humans allowed them to grow in numbers by decreasing populations of predatory animals.
Between AD 1 and 800, there was a temporary decay in population growth (Figure 6). During this period, there are many disasters in different parts of the world, so growth in one region was balanced by decline in another.
Man has found a new resource for food - people have learned to clear the land from trees and irrigate it. But over time, as the population grew, the resources available were distributed. It was around this time that they began to deplete. The land no longer gave the previous harvest. The wages the workers received fell and it became more difficult to feed. Epidemics began. The period of such decline can be graphically depicted as follows:
Figure 7. Graph of a typical long-term cycle of economic activity, built according to the data of Peter Turkin and Sergei Nefedov: growth - 100+ years, stagflation - 50-60 years, crisis - 20-50 years, transition period
So even between 1 and 800 AD, the population was not stable. In fact, at this time, in different places on the planet, there was either an increase or a decrease in the number so that the general level of the human population on the planet at that time did not change significantly.
Angus Maddison analyzed GDP growth from the 1st to the 1000th century AD. He concluded that GDP per capita declined slightly at the end of this period (453) compared to the beginning (476). According to his calculations, the state of the economy during the period from 1 to 800 A. D. was quite stable (with a large number of disasters), taking into account the lack of growth in the number and GDP per capita.
In the periods of history closer to us, people managed to master new sources of energy (including peat moss, wind and water mills). Well-equipped ships appeared, capable of transporting people to new lands, forming colonies and developing agriculture in new places, extracting resources and transporting them to their country.
Since 1800, thanks to the growth of fossil fuel extraction, there has been a sharp jump in the number of people and a significant increase in the standard of living.
Figure 8. World consumption of energy resources per year per person (blue - biofuel, red - coal, green - oil, lilac - natural gas, blue - hydro-electricity, orange - nuclear energy)
Is it possible to achieve a stable state, and how?
There are not many options at all:
1. If we go back to the period when our ancestors had not yet learned how to use fire, 100-200 thousand of us could live in a warm climate, eat raw food and live about the same life that baboons or chimpanzees live today. In this case, the human population would probably fluctuate within certain limits.
At present, human internal organs have adapted to cooked food, and how they would react to being completely raw is not entirely clear. However, it is quite possible that life in areas with an abundance of soft food (berries, fish) would be tolerable. In addition, the climate must be warm, so that we do not freeze without fur coats. For these conditions to be met, the population must be even smaller.
2. The absence of people in general, strictly speaking, can also be regarded as a stable state. However, the prospect of such stability is unlikely to suit any of us.
3. If we did not strive for globalization and stopped producing new reserves of energy, then the situation could be leveled out by local shocks like those that took place from 1 to 800 AD. This would also be a kind of steady state. However, in our global world, problems easily move from one part of the world to another.
4. If we want the 7 billion people to continue living, we need to provide them with a supply of energy at least at the most basic level. If we assume that for survival, today's person needs energy consumption at least at the level of 1820 (judging by the data shown in Fig. 8), then for each person there should be at least 22 gigajoules. This is approximately 7 percent of today's consumption. That is, we would have to do without transport, electricity, running water and sewage, so for us it would be a huge step back.
Even with an energy consumption of 1820, we would still have to partially use fossil fuels, because there are too many of us and biofuels alone would not be enough (Marked in blue in Figure 8)
In addition, renewable sources, including modern hydroelectric and solar panels, are also manufactured and transported using fossil fuels. Therefore, in order to use what we today consider as renewable sources, we must continue to extract fossil fuels.
In addition to all of the above, we will have to:
(a) reduce population growth
(b) prevent the use of available energy reserves (in excess of the designated 22 gigajoules per person) and achieve a fundamental change in lifestyle.
Often, measures such as raising the level of education for women and more opportunities for birth control are proposed as measures to keep the growth of the world's population within certain limits. Unfortunately, these measures are also related to energy consumption. In the conditions in question, a woman will have to work in the field from morning till night, and she simply will not have time for education.
Some cultures manage to keep the level of their population within certain limits by means that are not associated with the consumption of additional energy. In China, for example, strict birth control is imposed from above. In other countries, there are cultural and religious restrictions - delaying marriage, for example, or long breastfeeding.
It will be even more difficult to keep people from using available energy sources and change their lifestyle. To be limited to 7 percent of the energy that a person has consumed so far would mean losing almost everything to which he is used.
There is a common misconception that avoiding personal transportation can have a significant impact on the total amount of energy consumed. In America, for example, gasoline accounts for about 44 percent of oil consumption. If we subtract this resource from the total (including police cars, ambulances, and delivery of goods), we get a savings of only 16 percent. In the rest of the world, where not everyone has a personal car, the savings will be even less - on average 10-12 percent.
Should we strive for a sustainable economy?
At the present time, most likely, we are moving towards demographic collapse, since the growth of the human population has long been incomparable with the growth of populations of other species. In addition, we have many other constraints today, including the cost of producing oil, the availability of fresh water, and the level of air pollution.
The only stable state that would make sense is if humanity could voluntarily retreat in its development back to some lower level - as an alternative to collapse. Unfortunately, it is difficult to even imagine how to do this. The only period of relative stability in history is between 1 and 800 AD, when the growth of the human population in some regions of the place was balanced by a decrease in others. The periods when there was no increase in population at all, apparently, did not exist.
If, after the collapse, civilization slides to a lower level (but not to zero), then, most likely, it will repeat the same development model, over and over again. Man will again increase both the population size and the consumption of the resources available to him. This system is in our instincts and it seems useless to fight it.
Whatever we do, sooner or later a collapse will inevitably occur, and humanity will slide to a lower level of its development.