Ecology: biology of interaction. 6.03. Demographic transition

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6.02. Demographic explosion

D. Shabanov, M. Kravchenko. Ecology: biology of interaction Chapter 6. Human ecology and nature conservation

6.04. Can the size of the Earth’s population be limited?

6.03. Demographic transition What is the cause of the population growth described in the previous paragraph? One might think that higher birth rates mean that because there are more people, more are being born. Strangely, the opposite is true: the growth is linked to a change in the pattern of mortality. Naturally, everyone who is born will eventually die, but for population dynamics it is crucial when this occurs. The “burst” of humanity’s numbers at the end of the 20th century is associated with the replacement of pre‑reproductive (before the age of reproduction) mortality by post‑reproductive (after leaving offspring) mortality. In other words, a century ago most newborns died in the first days and months of life, whereas in recent decades most survived to reproductive age and left some offspring. The change in the birth‑mortality ratio that is accompanied by rapid population growth and then its stabilization is called the demographic transition. The concept was introduced by the American demographer Frank Notstein, who in 1945 synthesized both his own results and those of his predecessors. To understand why the population grows, it is necessary to determine under what conditions it remains constant. Population size does not change if each successive generation is the same size as the previous one. This is possible if, on average, each mature woman has one daughter who reaches maturity (or, assuming equal sex ratios, each pair of parents has two children who reach maturity). If all newborns survived to adulthood and eventually had children, two children per parental pair would be sufficient. Because at least a small fraction of people never reach reproductive age, and some never have children, even in societies with very low pre‑reproductive mortality more than two children per parental pair are needed to maintain a constant population size. In societies with underdeveloped medicine and high child mortality, many more children per pair are required. When only one in five newborns reaches reproductive age, a constant population corresponds to more than ten children per married couple (and per woman). As surprising as this number may seem for modern humans, it is normal for our species! A century ago such family sizes were quite typical. Medical advances have sharply reduced child mortality—first in “developed” countries and later in “developing” ones. Fortunately, child mortality is now falling rapidly, but this has little effect on birth rates. People born into large families also tend to have many children. Births far outpace deaths, and the population grows rapidly. Technological progress makes it possible to feed the much larger population. In the pre‑industrial era the overwhelming majority of people lived in villages. As the population grew, land allotments became insufficient for everyone; many peasant children moved to cities and began new lives. The break with traditional values and peasant culture leads people to have relatively few children. Finally, birth rates fall to a level that matches mortality. The population stabilizes, but at a much higher level than that characteristic of patriarchal societies. The described sequence of changes corresponds to the four stages of the demographic transition shown in Fig. 6.3.1. In the former Russian Empire and the USSR the transition occurred from 1885 to 1965. Overall, the demographic transition worldwide will be completed by 2050. [IMG_1] Fig. 6.3.1. Simplified scheme of the demographic transition (changes in mortality and birth rates due to social “maturation” and modern technologies). Compare with Fig. 6.3.2! Naturally, the scheme in Fig. 6.3.1 is simplified to the extreme. The dynamics of each human population are also influenced by other factors; even after mortality declines due to the medical revolution, it does not remain constant. Nevertheless, the real dynamics of mortality and fertility in actual human populations follow the demographic transition scheme (Fig. 6.3.2). [IMG_2] Fig. 6.3.2. Estimates of mortality and fertility (per 1 000 people per year) for England and Wales (1541–2015). The overall mortality and fertility trends (ignoring less significant tendencies) correspond to the scheme shown in Fig. 6.3.1 (source). In Phase I of the demographic transition, which corresponds to traditional societies, human populations are characterized by high mortality and high fertility. Because the population grows in Phase I, a typical case is when fertility on average exceeds mortality. Thanks to technological development, medical successes and the benefits of civilization, mortality declines, primarily through reduced child mortality. This characterizes Phase II of the demographic transition. Children survive more often, but the number of newborns remains the same, as it is determined by stable cultural ideas about the “right” family. Phase III of the demographic transition is marked by declining fertility. People gain the possibility to live for themselves, to plan families… and realize that having many children is not necessary. Fertility falls—sometimes to a level matching mortality, sometimes even below it. Finally, in Phase IV fertility and mortality stabilize at a new level. The events that follow one another during the demographic transition can also be described as the “melting” of rural populations into urban ones. In a peasant family, children are largely new labor hands. Older children help with agricultural work, middle children look after the younger ones. Large families prove more successful. In the urban environment, children begin to earn money later, usually after leaving their parents’ home. Prolonged childhood, schooling, and often higher education require substantial parental investment in each child. As a result, children become a burden. Even more important is that access to education for women and the spread of feminist values change each woman’s life priorities; she begins to think less about conforming to traditional notions of her role (“KKK: Kinder, Küche, Kirche”—children, kitchen, church) and more about her own development and career. Women increasingly give birth not when they are physiologically ready, but when they feel socially mature and ready for motherhood. The availability of contraceptives and family‑planning technologies allows sexual life to begin long before the first pregnancy. Ultimately, women start giving birth later and have far fewer children. “Child‑free” families or those deliberately limiting themselves to a single child become common in cities (a phenomenon unimaginable in traditional agricultural societies, where childless or small families are almost always the result of disease). Recently, when describing the demographic transition, scholars have added a V phase to Notstein’s scheme: a stage of new, “conscious” growth (Fig. 6.3.3). This only partially reflects current dynamics in the most developed countries and is probably mainly a nod to political correctness. Slow growth is the desired population state for most countries, and models are adjusted to fit this preferred outcome. Alternative concepts propose viewing the fifth phase as a period of mortality dominance and population decline. [IMG_3] Fig. 6.3.3. Demographic transition scheme with five stages (en.wikipedia.org) Despite the controversy over defining a V phase, Fig. 6.3.3 successfully shows the link between transition dynamics and demographic changes. Thus, in Phases II and III the population “youthens” strongly—its significant share consists of young people. Conversely, after reaching Phase IV the share of elderly people in society begins to rise rapidly. The global human population is distributed very unevenly across the planet. Population density is roughly illustrated in Fig. 6.3.4. The top‑10 countries by population size (as of 2020) are: China (1.439 billion), India (1.380 billion), United States (331 million), Indonesia (274 million), Pakistan (221 million), Brazil (213 million), Nigeria (206 million), Bangladesh (165 million), Russia (146 million) and Mexico (129 million). [IMG_4] Fig. 6.3.4. Population density (according to the English Wikipedia). The colour scale, calibrated in people per square kilometre, is shown in the inset. Uneven distribution of humanity also appears when comparing different countries (Table 6.3.1). Table 6.3.1. Comparison of demographic indicators for selected countries (Worldometers project data, 2020) | Country | Population (million) | Annual growth | Population density (people/km²) | Area (thousand km²) | Migrants (million/year) | Avg. children per woman | Median age (years) | Urban population % | |---|---|---|---|---|---|---|---|---| | China | 1439 | 0.39 % | 153 | 9388 | –0.349 | 1.69 | 38 | 61 % | | India | 1380 | 0.99 % | 464 | 2973 | –0.533 | 2.24 | 28 | 35 % | | USA | 331 | 0.59 % | 36 | 9147 | 0.955 | 1.78 | 38 | 83 % | | Nigeria | 206 | 0.72 % | 226 | 910 | –0.060 | 5.4 | 18 | 52 % | | Bangladesh | 165 | 1.01 % | 1265 | 130 | –0.370 | 2.05 | 28 | 39 % | | Russia | 146 | 0.04 % | 9 | 16377 | 0.182 | 1.82 | 40 | 74 % | | Japan | 126 | –0.30 % | 347 | 364 | 0.071 | 1.4 | 48 | 92 % | | Germany | 84 | 0.32 % | 240 | 349 | 0.544 | 1.6 | 46 | 76 % | | Ukraine | 44 | –0.59 % | 75 | 579 | 0.010 | 1.4 | 41 | 69 % | | Poland | 38 | –0.11 % | 124 | 306 | –0.029 | 1.4 | 42 | 60 % | | Somalia | 16 | 2.92 % | 25 | 627 | –0.040 | 6.1 | 17 | 47 % | | Belarus | 9.4 | –0.03 % | 47 | 203 | 0.008 | 1.7 | 40 | 79 % | | Israel | 8.6 | 1.60 % | 400 | 21 | 0.010 | 3.0 | 30 | 93 % | | Singapore | 5.8 | 0.79 % | 8 | 725 | 0.027 | 1.2 | 42 | — | | Finland | 5.5 | 0.15 % | 18 | 303 | 0.014 | 1.5 | 43 | 86 % |

Country

Population, million.

Table 6.3.1. Comparison of demographic indicators for selected countries (Worldometers project data, 2020)

Population density, people/km²

Area, thousand km²

Number of migrants, million per year

Average number of offspring per woman

Average age, years

Proportion of urban population

China

1439

0,39%

153

9388

-0,349

1,69

38

61%

India

1380

0,99%

464

2973

-0,533

2,24

28

35%

USA

331

0,59%

36

9147

0,955

1,78

38

83%

Nigeria

206

0,72%

226

910

-0,060

5,4

18

52%

Bangladesh

165

1,01%

1265

130

-0,370

2,05

28

39%

Russia

146

0,04%

9

16377

0,182

1,82

40

74%

Японія

126

-0,30%

347

364

0,071

1,4

48

92%

Germany

84

0,32%

240

349

0,544

1,6

46

76%

Ukraine

44

-0,59%

75

579

0,010

1,4

41

69%

Poland

38

-0,11%

124

306

-0,029

1,4

42

60%

Сомалі

16

2,92%

25

627

-0,040

6,1

17

47%

Belarus

9,4

-0,03%

47

203

0,008

1,7

40

79%

Ізраїль

8,6

1,60%

400

21

0,010

3,0

30

93%

Singapore

5,8

0,79%

8

725

0,027

1,2

42

Finland

5,5

0,15%

18

303

0,014

1,5

43

86%

Tabular data are not easy to digest, but Table 6.3.1 provides valuable opportunities for comparing our country with others and understanding our specific features. Regarding population decline (despite migrant inflows), our country is one of the world leaders. Unfortunately, this is linked not so much to our high level of development as to the perception of the situation by our citizens. Declining living standards and abandonment of previously set goals can lead to a depressive worldview. Since Ukraine is a priority target for the world’s most powerful brain‑washing systems, catastrophic perception of reality is typical for the average person who judges the world by what is shown on television. From an economic standpoint, countries are usually divided into developed and developing. This division is rather conventional; there are no strict criteria for distinguishing such countries. “A developed country is one that enables all its residents to enjoy a free and healthy life in a safe environment.” – Kofi Annan. Today many “developing” countries have powerful and dynamic economies, and the most characteristic features of this group are the traits of their populations. “Developed” countries have stable or declining populations with a significant share of elderly people (Fig. 6.3.5). Populations of “developing” countries remain young and grow rapidly (Fig. 6.3.6). [IMG_5] Fig. 6.3.5. Change in the share of young and elderly people on average for humanity as a whole. Future data correspond to UN forecasts. [IMG_6] Fig. 6.3.6. Demographic pyramids typical for “developed” and “developing” countries The technologies that have enabled the current growth of humanity were developed in “developed” countries. The success of these nations is a consequence of introducing such technologies in health care, industry and agriculture. After modern technologies transformed “developed” countries, they were exported to “developing” ones, which caused a significant rise in their populations. Differences in population dynamics only increase the global economic disproportion: the overwhelming majority of economic assets belong to “developed” countries; these same countries consume the vast majority of resources used by humanity. Naturally, such disproportion leads to growing tension between poor and rich nations. For now, “developed” countries can maintain their status thanks to a substantial military advantage. However, over time this situation may change. The share of the population of “developed” countries in the world’s total will continue to decline. The nature of modern conflicts also changes. Greater importance will be attached not to clashes of regular armies but to the ability to deliver swift and precise strikes against the enemy. Such strikes can be carried out with high‑precision weapons or by using terrorist groups. Could this mean that an increased level of aggression among different human groups will slow population growth? No. At the current stage, in “developing” countries with their large young populations, catastrophes and wars have little impact on population growth! Today 3–6 million people die each year from hunger and inadequate nutrition, but these losses are compensated by births within a few days. “Social and cultural factors more than anything else determine fertility levels. The most important is the role women play in the family, the economy and society as a whole. The fertility rate declines as women’s opportunities for employment outside the home and farm expand, as their access to education increases and the age of marriage rises… Poverty generates high population growth rates. Families with low incomes and insufficient social security need children, first to involve them in work and then to feed their parents.” (Report of the UN International Commission on Environment and Development, 1987). Uneven food production can be partially offset by redistribution, for example through so‑called humanitarian aid that wealthy countries provide to the poor. However, humanitarian assistance can create new problems. One such issue is called the “extremely sad theorem.” Cheap food surpluses from developed countries sent to starving regions provide short‑term relief but long‑term aggravation of hunger by undermining local producers. The leading aid concept adopted now by Western countries is “appropriate technology.” Its components are: — direct satisfaction of population needs without destroying existing social structures; — low requirements for education and skill levels; emphasis on methods that citizens can teach each other; — use of abundant and cheap local resources; — reliance on existing material support and small‑scale producers. By solving the most acute problems, such aid preserves the differences between “developed” and “developing” nations. A typical reaction of citizens in “developing” countries to this aid is fear of being locked in the past. Conversely, in the long term it may turn out that an economy of “developed” countries, which relies on massive consumption of fossil energy, will be more vulnerable to inevitable restructurings than the relatively primitive economies of “lagging” nations. 6.02. Demographic explosion

D. Shabanov, M. Kravchenko. Ecology: biology of interaction Chapter 6. Human ecology and nature conservation

6.04. Can the size of the Earth’s population be limited?

6.04. Чи можна обмежити чисельність населення Землі?