# Population, Urbanization, and the Environment

## Demography and Population

Between 2011 and 2012, we reached a population milestone of 7 billion humans on the earth’s surface. The rapidity with which this happened demonstrated an exponential increase from the time it took to grow from 5 billion to 6 billion people. In short, the planet is filling up. We'll have 8 billion people in this decade. While the population is increasing overall, there are certain countries and regions where growth is slowing. Relocation and migration also change the makeup and quantity of people in an area. In order to properly understand these dynamics and make decisions regarding them, we turn to demography, or the study of populations. Three critical aspects of demography are fertility, mortality, and migration.
The fertility rate of a society is a measure noting the number of children born. The fertility number is generally lower than the fecundity number, which measures the potential number of children that could be born to women of childbearing age. Sociologists measure fertility using the crude birthrate (the number of live births per 1,000 people per year). Just as fertility measures childbearing, the mortality rate is a measure of the number of people who die. The crude death rate is a number derived from the number of deaths per 1,000 people per year. When analyzed together, fertility and mortality rates help researchers understand the overall growth occurring in a population.
Another key element in studying populations is the movement of people into and out of an area. Migration may take the form of immigration, which describes movement into an area to take up permanent residence, or emigration, which refers to movement out of an area to another place of permanent residence. Migration might be voluntary (as when college students study abroad), involuntary (as when Syrians evacuated war-torn areas), or forced (as when many Native American tribes were removed from the lands they’d lived in for generations). 
A functional perspective theorist might focus on the dysfunctions caused by the sudden influx of underage asylum seekers, while a conflict perspective theorist might look at the way social stratification influences how the members of a developed country are treating the lower-status migrants from less-developed countries in Latin America. An interactionist theorist might see significance in the attitude of those protesting the presence of migrant children. Which theoretical perspective makes the most sense to you?

### Population Growth

Changing fertility, mortality, and migration rates make up the total population composition, a snapshot of the demographic profile of a population. This number can be measured for societies, nations, world regions, or other groups. The population composition includes the sex ratio, the number of men for every hundred women, as well as the population pyramid, a picture of population distribution by sex and age ().
Comparing the three countries in  reveals that there are more men than women in Afghanistan and Finland, whereas the reverse is true in the United States. Afghanistan also has significantly higher fertility and mortality rates than either of the other two countries. In all three cases, the fertility rates have dropped in recent years, but Afghanistan's drop (from 5.4 children per woman to 4.4) will likely be the most impactful (World Bank 2019). Do these statistics surprise you? How do you think the population makeup affects the political climate and economics of the different countries?

### Demographic Theories

Sociologists have long looked at population issues as central to understanding human interactions. Below we will look at four theories about population that inform sociological thought: Malthusian, zero population growth, cornucopian, and demographic transition theories.

### Malthusian Theory

Thomas Malthus (1766–1834) was an English clergyman who made dire predictions about earth’s ability to sustain its growing population. According to Malthusian theory, three factors would control human population that exceeded the earth’s carrying capacity, or how many people can live in a given area considering the amount of available resources. Malthus identified these factors as war, famine, and disease (Malthus 1798). He termed them “positive checks” because they increase mortality rates, thus keeping the population in check. They are countered by “preventive checks,” which also control the population but by reducing fertility rates; preventive checks include birth control and celibacy. Thinking practically, Malthus saw that people could produce only so much food in a given year, yet the population was increasing at an exponential rate. Eventually, he thought people would run out of food and begin to starve. They would go to war over increasingly scarce resources and reduce the population to a manageable level, and then the cycle would begin anew.
Of course, this has not exactly happened. The human population has continued to grow long past Malthus’s predictions. So what happened? Why didn’t we die off? There are three reasons sociologists believe we are continuing to expand the population of our planet. First, technological increases in food production have increased both the amount and quality of calories we can produce per person. Second, human ingenuity has developed new medicine to curtail death from disease. Finally, the development and widespread use of contraception and other forms of family planning have decreased the speed at which our population increases. But what about the future? Some still believe Malthus was correct and that ample resources to support the earth’s population will soon run out.

### Zero Population Growth

A neo-Malthusian researcher named Paul Ehrlich brought Malthus’s predictions into the twentieth century. However, according to Ehrlich, it is the environment, not specifically the food supply, that will play a crucial role in the continued health of the planet’s population (Ehrlich 1968). Ehrlich's ideas suggest that the human population is moving rapidly toward complete environmental collapse, as privileged people use up or pollute a number of environmental resources such as water and air. He advocated for a goal of zero population growth (ZPG), in which the number of people entering a population through birth or immigration is equal to the number of people leaving it via death or emigration. While support for this concept is mixed, it is still considered a possible solution to global overpopulation. 

### Cornucopian Theory

Of course, some theories are less focused on the pessimistic hypothesis that the world’s population will meet a detrimental challenge to sustaining itself. Cornucopian theory scoffs at the idea of humans wiping themselves out; it asserts that human ingenuity can resolve any environmental or social issues that develop. As an example, it points to the issue of food supply. If we need more food, the theory contends, agricultural scientists will figure out how to grow it, as they have already been doing for centuries. After all, in this perspective, human ingenuity has been up to the task for thousands of years and there is no reason for that pattern not to continue (Simon 1981).

### Demographic Transition Theory

Whether you believe that we are headed for environmental disaster and the end of human existence as we know it, or you think people will always adapt to changing circumstances, we can see clear patterns in population growth. Societies develop along a predictable continuum as they evolve from unindustrialized to postindustrial. Demographic transition theory (Caldwell and Caldwell 2006) suggests that future population growth will develop along a predictable four-stage model.
In Stage 1, birth, death, and infant mortality rates are all high, while life expectancy is short. An example of this stage is the 1800s in the United States. As countries begin to industrialize, they enter Stage 2, where birth rates are higher while infant mortality and the death rates drop. Life expectancy also increases. Afghanistan is currently in this stage. Stage 3 occurs once a society is thoroughly industrialized; birth rates decline, while life expectancy continues to increase. Death rates continue to decrease. Mexico’s population is at this stage. In the final phase, Stage 4, we see the postindustrial era of a society. Birth and death rates are low, people are healthier and live longer, and society enters a phase of population stability. Overall population may even decline. For example, Sweden is considered to be in Stage 4.
The United Nations Population Fund (2008) categorizes nations as high fertility, intermediate fertility, or low fertility. The United Nations (UN) anticipates the population growth will triple between 2011 and 2100 in high-fertility countries, which are currently concentrated in sub-Saharan Africa. For countries with intermediate fertility rates (the United States, India, and Mexico all fall into this category), growth is expected to be about 26 percent. And low-fertility countries like China, Australia, and most of Europe will actually see population declines of approximately 20 percent. The graphs below illustrate this trend.

### Changes in U.S. Immigration Patterns and Attitudes

Worldwide patterns of migration have changed, though the United States remains the most popular destination. From 1990 to 2013, the number of migrants living in the United States increased from one in six to one in five (The Pew Research Center 2013). Overall, the United States is home to about 45 million foreign-born people, while only about 3 million U.S. citizens lived abroad. Of foreign-born citizens emigrating to the United States, 55 percent originated in Latin America and the Caribbean. However, over the past few years, more people from Asian countries have entered than from Latin American ones (Budiman 2020).
While there are more foreign-born people residing in the United States legally, as of 2017 about 10.5 million resided here without legal status (Budiman 2020). Most immigrants in the U.S. live in either Texas, Florida, or California.
Even before policy changes and COVID-19 affected refugee admittance, a relatively small number of people formally entered the country as refugees. In 2016, about 85,000 refugees were admitted to the U.S. (of over one million total immigrants), with the largest portion arriving from the Democratic Republic of Congo; in 2020, the number of refugees was reduced to 18,000.
Most citizens agree that our national immigration policies are need adjustment. More than two-thirds (69 percent) of those in a recent national survey believed illegal immigrants should have a path to citizenship provided they meet other requirements, such as paying taxes and passing a background check. Even more people (72 percent) supported passing a DREAM Act, which would allow people who immigrated as children to earn citizenship. In both parts of the survey, majorities of both Republicans and Democrats as well as independents supported the pathway to citizenship (Vox and Data for Progress 2021).

### Summary

Scholars understand demography through various analyses. Malthusian, zero population growth, cornucopian theory, and demographic transition theories all help sociologists study demography. The earth’s human population is growing quickly, especially in peripheral countries. Factors that impact population include birthrates, mortality rates, and migration, including immigration and emigration. There are numerous potential outcomes of the growing population, and sociological perspectives vary on the potential effect of these increased numbers. The growth will pressure the already taxed planet and its natural resources.

### Section Quiz


### Short Answer


### Further Research

To learn more about population concerns, from the new-era ZPG advocates to the United Nations reports, check out the Population Connection web site.
Explore an interactive version of the population pyramid for each country, and to see updates and changes over time: at this website.

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