PH 304 - Module 2 - Ken Calvert PDF

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2/2/2021

2b - Some Important Terms: P_H304-01: Environment and Public Health

2b - Some Important Terms Population Terms As we begin our discussion of population, it will be important that we learn some commonly used terms and concepts.

Limiting Factors

Are those factors within an environment without which population growth isn't possible. These often appear as basic nutrients or space.

Biotic Potential

Is the maximum growth rate in an ideal environment. This is absent any limiting factors.

Is the difference between the biotic potential of a population and the Environmental actual rate of increase. This difference is due to certain limiting factors Resistance such as food and space availability, disease and predation and accumulation of wastes. Carrying Capacity

Is the limit of population growth imposed by the environment. This includes the impacts of all limiting factors and environmental resistance within the environment.

Homeostatic Controls

Are behavioral changes that occur as a result of certain population pressures like overcrowding or scarcity of food.

Productivity (Support Ratio)

Is a measure of the number of dependents or the ratio of those who are too young or old to work to those who are working. In the US two people work for every one person who is too young or too old. In Mexico one person works for every two persons who don’t.

S-Population Curve Population of any organism can follow one of several growth curves. The S-curve represents an initially exponential growth, then a steep https://sdsu.instructure.com/courses/55652/pages/2b-some-important-terms?module_item_id=606039

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2b - Some Important Terms: P_H304-01: Environment and Public Health

growth followed by exponential decline as growth reaches an upper asymptote. This balance is called the carrying capacity and is the biotic potential mitigated by an increase in mortality due to the influence of limiting factors. Growth slowly approaches the carrying capacity without actually reaching it.

J-Population Curve J-Curve – is essentially identical to the s-curve except limiting factors don’t have effect until the last moment resulting in rapid population die-off. Population might briefly meet or exceed the carrying capacity before die-off.

Growth Age Structure This population chart shows the number of people by age group. Large numbers of young people in developing countries guarantee large population growth.

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2b - Some Important Terms: P_H304-01: Environment and Public Health

Population Momentum - When there are large numbers of young people in a population, even if fertility were to drop below replacement levels, population will continue to increase for many years due to the high percentage of people entering childbearing age. Each generation will be successively smaller to the extent fertility remains below replacement.

Static Age Structure This population chart shows the number of people by age group. Fewer young people in developed countries ensures little population growth or even population decline. Support ratio - The ratio of those working divided by the number of people too old or too young to work. Countries with this age structure will experience declining support ratio's as the average age of the population increases.

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2b - Some Important Terms: P_H304-01: Environment and Public Health

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2c - Demographic Transition: P_H304-01: Environment and Public Health

2c - Demographic Transition Agricultural Economies Humans have been agriculturalists for at least 12,000 years. During that time, our economy and our culture developed surrounding the demands of agriculture. It became the rhythm of our lives. In an agricultural economy, children are always an asset. They represent labor, social security, and a kind of immortality. Ideal family size is culturally and pragmatically defined and socially reinforced.

Demographic Transition Characterized by high birth rate and high death rate. High death rates are Phase 1: due to: warfare, disease, poverty. Characterized by a young population of pre-industrial constant size (Rwanda in the 1990’s was the last country considered to still be in Phase 1)

Phase 2: Boom

Characterized by rapidly declining death rates and slightly declining birth rates. Improvement in death rate and life expectancy is due to improved sanitation, health care, and standard of living. Population booms as death rate declines.

Phase 3: Still Rising

Characterized by slightly declining death rates and rapidly declining birth rates. Birth rates decline as women gain access to education and practice family planning. Momentum from the Phase 2 boom continues to increase population rapidly. Birth rate is still significantly above death rate.

Population stabilizes as births and deaths come into balance. Birthrate Phase 4: drops to replacement and often below replacement. Death rate remains Replacement low or rises due to a growing older population and increase in chronic Fertility disease

Phase 5: Declining Population

Characterized by birth rates well below replacement. Many countries and areas have experienced birth rates well below replacement. As younger population declines the dependency ratio increases resulting in declining standard of living. Migration and prolonged retirement are implemented to off-set social impacts.

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2c - Demographic Transition: P_H304-01: Environment and Public Health

Fertility Total Fertility Rate Total Fertility Rate (TFR) is an important measure of population growth which represents the total number of children each woman, on average, will bare per lifetime. In the past, child mortality was quite high and it required a TFR of 4 or more children to replace both parents. However, as child mortality decreases, women choose to have fewer children in an effort to raise them better, and TFR subsequently decreases. This is considered to be largely economically driven and coincides with improvements in health and the transition from an agricultural to an industrial workforce. There is a direct correlation between: 1. 2. 3. 4.

Child mortality Standard of Living Education of Women And ideal family size.

Replacement Fertility: Currently replacement fertility is considered 2.1 meaning that for most of the world child mortality is low. Currently 2.1 children per woman per lifetime will replace both parents. However, prior to the industrial revolution replacement fertility was higher and it required 4 or more children to replace both parents because so many children were lost before the age of 5. Note that roughly half of the countries in the world are declining in population https://sdsu.instructure.com/courses/55652/pages/2c-demographic-transition?module_item_id=606040

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2c - Demographic Transition: P_H304-01: Environment and Public Health

(TFR below 2.1) and half are increasing (TFR above 2.1). However, TFR rates are rapidly declining in all countries.

Demographic Transition by Country The main measure of where a country might be, in terms of its demographic transition, is the Total Fertility Rate (TFR). The chart on the right shows the percentage of countries in the various stages of transition. TFR rates are currently declining in all countries. Phase 1: TFR 5+ Phase 2: TFR 3.5-5 Phase 3: TFR 2-3.5 Phase 4 TFR 1.5-2 Phase 5 TFR below 1.5

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2d - Projected Rate of World Growth: P_H304-01: Environment and Public Health

2d - Projected Rate of World Growth Current and Projected World Population The population that exists today, like every population that has ever existed, is historically unprecedented. The prospects of feeding that population is likewise unprecedented. The challenges of a warming climate, declining water reserves, and a decline of soil productivity make this challenge formidable, but not impossible. There is inherent uncertainty in population projections that depend on assumptions about plausible future trends in specific demographic variables. Those assumptions include: 1. A continuing decline of fertility in countries where large families are still prevalent. 2. A slight increase in fertility in countries where women have fewer than two live births. 3. That death rates will continue to decline in all countries. Recently, the World Bank and World Health Organization have demonstrated increasing accuracy in predicting world population giving them increased credibility in forecasting future trends. In addition, more countries have consistently provided better data than in the past. The world’s population numbered nearly 7.8 billion as of mid-2020, implying that the world has added approximately one billion inhabitants over the last twelve years. World population is projected to reach 8 billion before 2023.

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2d - Projected Rate of World Growth: P_H304-01: Environment and Public Health

The Past In historical terms, 1804 was yesterday. Population growth looks more like a left turn than a geometric growth. Even so, the rate at which1 billion people are added is declining. However, there's no way to look at these numbers without alarm. Year

Population

Years to add 1 billion people

1804

1 billion

200,000 years +

1922

2 billion

118 years

1959

3 billion

37 years

1974

4 billion

15 years

1987

5 billion

13 years

1999

6 billion

12 years

2011

7 billion

14 years

The Malthusian Trap This 2018 video by Joe Scott is a little dated but I think the issues he addresses are still relevant today.

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2d - Projected Rate of World Growth: P_H304-01: Environment and Public Health

Today World population is distributed in dramatically different ways 60% of the world’s people live in Asia (4.6 billion). 17 % in Africa (1.3 billion) 9.6 % in Europe (747 million) 4. 7 % in Latin America and the Caribbean (653 million), 5.2 % in Northern America (369 million) and Oceania (43 million). China (1.43 billion) and India (1.37 billion) remain the two most populous countries of the world, comprising 18.5 and 17.7 per cent of the global total, respectively.

The Future India will surpass China’s population in 2027. According to UN data, with a certainty of 95 per cent, the size of the global population will stand between: 8.4 and 8.7 billion in 2030 9.4 and 10.2 billion in 2050 9.6 and 13.2 billion in 2100 Continued increase in global population is considered the most likely outcome: There is roughly a 27 % chance that the world’s population could stabilize or even begin to fall sometime before 2100. https://sdsu.instructure.com/courses/55652/pages/2d-projected-rate-of-world-growth?module_item_id=606043

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2d - Projected Rate of World Growth: P_H304-01: Environment and Public Health

Uneven Growth

More than half of the anticipated growth in global population between now and 2050 is expected to occur in Africa. Asia is expected to be the second largest contributor to this future growth, adding just over 750 million people between 2017 and 2050. Africa and Asia will be followed by Latin America and the Caribbean, Northern America and Oceania, where growth is projected to be much more modest. Europe is the only region with a smaller population in 2050 than today. Beyond 2050, Africa will be the main contributor to global population growth.

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2e - A Decline in the Rate of Increase: P_H304-01: Environment and Public Health

2e - A Decline in the Rate of Increase Universal Population Decline Although the world’s population is expected to continue growing until the end of the 21st century, the rate at which this growth will occur is expected to continue to fall.

Africa In recent years, the population of Africa has had the fastest growth among all regions, increasing at a rate of 2.6% annually in 2010-2015; however, this rate is beginning to fall and is projected to reach https://sdsu.instructure.com/courses/55652/pages/2e-a-decline-in-the-rate-of-increase?module_item_id=606045

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2e - A Decline in the Rate of Increase: P_H304-01: Environment and Public Health

1.8% in 2045-2050 and 0.66% in 2095-2100. After 2050, it is expected that Africa will be the only region still experiencing substantial population growth. As a result, Africa’s share of global population, which grew from roughly 17% in 2017, and is projected to increase around 26% in 2050, could reach 40% by 2100. At the same time, the share residing in Asia, currently estimated as 60 per cent, is expected to fall to around 54% in 2050 and 43% in 2100. The population of Africa will continue to increase in future decades, even if the number of births per woman falls instantly to “replacement-level fertility”. Growth continues due to the average age of the population. Children and youth will enter childbearing age in future decades, further increasing population, even assuming that they will bear fewer children on average than their parents’ generation. In all plausible scenarios of future trends, Africa will play a central role in shaping the size and distribution of the world’s population over the next few decades.

The Least Developed Have the Biggest Challenge Population growth remains especially high in the group of 47 countries designated by the United Nations as the least developed countries (LDCs), including 33 countries in Africa. Although the growth of LDCs is projected to slow from its current annual rate of 2.4%, the population of this group is projected to nearly double in size from 1 billion inhabitants in 2017 to 1.9% billion in 2050, and to increase further to 3.2 billion in 2100. Between 2020 and 2100, the populations of 33 countries, most of them LDCs, have a high probability of at least tripling in size. Among them, the populations of Angola, Burundi, Niger, Somalia, the United Republic of Tanzania and Zambia are projected to be at least five times as large in 2100 as they are today. The concentration of population growth in the poorest countries will make it harder for those governments to eradicate poverty, reduce inequality, combat hunger and malnutrition, expand and update education and health systems, improve the provision of basic services and ensure that no-one is left behind.

Eastern Europe In sharp contrast, the populations of another 51 countries or areas of the world are expected to decrease between 2020 and 2050. Several countries are expected to see their populations decline by more than 15% by 2050, including Bulgaria, Croatia, Latvia, Lithuania, Poland, Republic of Moldova, Romania, Serbia, Ukraine and the Virgin Islands.

Europe https://sdsu.instructure.com/courses/55652/pages/2e-a-decline-in-the-rate-of-increase?module_item_id=606045

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2e - A Decline in the Rate of Increase: P_H304-01: Environment and Public Health

Fertility in all European countries is now below the level required for replacement of the population in the long run (around 2.1 births per woman, on average) and, in most cases, has been below the replacement level for several decades. Fertility for Europe as a whole is projected to increase from 1.6 births per woman in 2010-2015 to nearly 1.8 in 2045-2050. Such an increase, however, will not prevent a likely contraction in the size of the total population.

The Big 6 Much of the overall increase in population between now and 2050 is projected to occur either in high fertility countries, mostly in Africa, or in countries with large populations. From 2020 to 2050, it is expected that nearly half of the world’s population growth will be concentrated in just six countries: India, Nigeria, Congo, Pakistan, Ethiopia, and Tanzania.

India and China The new projections include some notable findings at the country level. For example, in roughly six years, the population of India is expected to surpass that of China. Currently, the population of China is approximately 1.44 billion compared with 1.38 billion in India. Thereafter, India’s population is projected to continue growing for several decades to around 1.5 billion in 2030 and approaching 1.66 billion in 2050, while the population of China is expected to remain stable until the 2030s, after which it may begin a slow decline.

Nigeria Nigeria’s population, currently the seventh largest in the world, is growing the most rapidly. The population of Nigeria is projected to surpass that of the United States shortly before 2050, at which point it would become the third largest country in the world. In 2050, the populations in six of the ten largest countries are: India, China, Nigeria, United States, Indonesia, and Pakistan.

Declining Rate of Growth Growth Rate – expressed as a percentage is equal to (birth rate – death rate) * 100. Most industrialized countries have growth rates well under 1 and range from -.5 (Russia) to .6 (USA).

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2e - A Decline in the Rate of Increase: P_H304-01: Environment and Public Health

Non-industrialized countries have growth rates from 1% (China) to 3% (Nigeria). Nigeria has a doubling time of 24 years. A growth rate of just 1% means that population will double in about 70 years.

Globally, the growth rate of the human population has been declining since peaking in 1962 and 1963 at 2.20% per annum. In 2009, the estimated annual growth rate was 1.1%. The current world growth rate is 1.08% or a doubling time of 70 years. Annual Growth - The actual annual growth in the number of humans fell from its peak of 88.0 million in 1989, to a low of 73.9 million in 2003, after which it rose again to 75.2 million in 2006. Since then, annual growth has declined. Future Decline in Growth - In 2009, the human population increased by 74.6 million, which is projected to fall steadily to about 41 million per annum in 2050. Each region of the globe has seen great reductions in growth rate in recent decades, though growth rates remain above 2% in some countries of the Middle East and Sub-Saharan Africa, and also in South Asia, Southeast Asia, and Latin America.

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