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Chapter 3
Migration
Since humans first left Africa sixty thousand years ago, ours has been a story of migration. From our origin on the African continent, we have settled all corners of the world, from within the Arctic Circle in the north to Tierra del Fuego in the south, from the most remote parts of Siberia to the jungles of Brazil. Only Antarctica has been spared human migrations, although even there a small number of scientists live on a temporary basis.
But humans have not been content to stay in place since settling the far reaches of our planet. We continue to move in search of better opportunities for our families or, all too often, as others force us to go elsewhere. Migration affects economies, environments, and cultures in profound ways. Migrants can help boost economic growth, as new workers provide needed labor in agriculture, manufacturing, and service enterprises. They can also send money back home, helping to improve the places they came from. But at the same time, migration can threaten the jobs of native workers, leading to societal tension and political battles, or lead to broken families and a lack of workers in the places they left. The movement of people and the mixing of languages, religions, customs, and beliefs can add vibrancy to places but can also strain social cohesion. Consequently, migration is one of the most important aspects of human geography (figure 3.1).
In Chapter 2, we were introduced to the demographic equation, which was stated as:
Population change = Births – Deaths + Immigration – Emigration
Obviously, birth and death rates help determine population size and population density on the surface of the earth. But that is only half of the equation. To make our explanation of these patterns complete, we must add one more component: migration. Migration is defined as the change in location of one’s permanent or semi-permanent residence. Thus, the population of a particular place is determined by the number of births and the number of deaths, as well as the number of people who migrate in and the number of people who migrate out. Immigration refers to in-migration; thus, we talk about immigrants who come from other countries to the United States. Emigration refers to out-migration, so those leaving, say, Mexico, for work abroad are called emigrants.
Migration (both immigration and emigration) can be analyzed at a variety of scales. International migration patterns are those between countries, such as between Mexico and the United States. But we also discuss national migration patterns, such as from the Northeastern United States to the Southwest. We can also examine local migration patterns, such as from rural areas to cities, known as rural-to-urban migration, and other moves within states or even within counties or cities.
Figure 3.1.US Immigrants, 1910 and 2016. Human migration is an ongoing phenomenon. Immigrants to Ellis Island c.a. 1910 and a naturalization ceremony in Portland, Oregon, in 2016. Photo by Bain, George Grantham. Immigrants, Ellis Island. ca. 1910. Library of Congress Prints and Photographs Division Washington, DC. 20540 USA. Photo by Diego G. Diaz, Royalty-free stock photo ID: 483311986. Shutterstock.
Spatial distributions
Migrant stock and flow
Before we discuss why people migrate, it is useful to look at the spatial distribution of migrants. This distribution can be viewed in terms of stock and flows. Migrant stock is the number of people who reside in a place where they were not born. When viewed as a percentage, it can show the proportion of the population that is not native to a place. While measures of migrant stock reflect the number of newcomers to a place, they do not tell when the people migrated there. Thus, migrant stock includes recent arrivals as well as migrants who may have arrived decades ago as children.
Migrant flows refer to migration within a certain timeframe. A count of the number of people moving into and out of a place within the past year represents a migration flow. Flows can be viewed in different time frames, so