Unit 2 Human Geography APHG Explained: Population & Migration

Unit two of AP Human Geography is population and migration patterns and processes. This unit explains where people live, why populations grow or decline, and why people move. It begins with population distribution, the pattern of where people live on Earth. Populations are clustered in areas with fertile soil, water access, moderate climate, and economic opportunity. Sparse populations are common in deserts, mountains, dense forests, and polar regions. Geographers study density to measure how crowded a place is. Arithmetic density is the total number of people divided by total land area. Physiological density is the number of people per unit of arable land showing pressure on farmland. Agricultural density is the number of farmers per unit of arable land showing how efficiently agriculture is organized. These measurements help compare regions and understand resource use. Another key term is carrying capacity, the number of people an environment can sustainably support. Next, students study population composition, which means the structure of a population by age, sex, and other traits. Geographers use a population pyramid, a bar graph that shows age groups and gender. A wide base suggests high birth rates and rapid growth. A more rectangular shape suggests slower growth and longer life expectancy. A narrow base may indicate declining birth rates and an aging society. Population pyramids help governments predict future needs for schools, housing, health care, and retirement systems. Countries with many young dependents may need jobs and education, while aging countries may need more health care workers and pension funding. This connects to the idea of the dependency ratio, the number of people too young or too old to work compared with the working age population. The next major topic is population change over time. Geographers use several statistics. The crude birth rate is the number of live births per 1,000 people each year. The crude death rate is the number of deaths per 1,000 people each year. The natural increase rate is the birth rate minus the death rate, not including migration. If births exceed deaths, population grows. If deaths exceed births, population declines. Other important terms include total fertility rate, the average number of children a woman is expected to have, and infant mortality rate, the number of infant deaths per 1,000 live births, and life expectancy, the average number of years a person is expected to live. These indicators often reflect health care access, nutrition, sanitation, and economic development. The key model in this section is the demographic transition model or DTM. In stage one, both birth and death rates are high, so growth is low. In stage two, death rates fall because of better food and medicine, but birth rates stay high, causing rapid growth. In stage three, birth rates decline as urbanization, education, and women's opportunities increase. In stage four, both birth and death rates are low, creating stable growth. Some geographers add stage five, where birth rates fall below death rates, causing decline. Students then examine theories about population growth. Thomas Malthus argued that population could grow faster than food supply, creating famine and conflict. His ideas are called Malthusian theory. Later scholars developed neo-Malthusian concerns about environmental limits and resource depletion. Others point to technology, innovation, and trade as ways societies can support larger populations. Governments sometimes respond with population policies. Pronatalist policies encourage larger families through tax breaks or child care support. Antinatalist policies attempt to reduce birth rates, such as China's former one-child policy. Students should analyze both intended and unintended consequences of these policies. Migration is the second half of unit two. Migration is permanent relocation to a new place. Internal migration happens within a country, such as rural to urban movement. International migration crosses national borders. Voluntary migration occurs when people choose to move for jobs, education, or family reasons. Forced migration happens when people are compelled to move by war, slavery, persecution, or disaster. Refugees flee across borders for safety, while internally displaced persons remain within their own country. Migration often changes population patterns, labor markets, and cultural landscapes. Students must also know push factors and pull factors. Push factors drive people away from a place, including unemployment, violence, drought, or political instability. Pull factors attract people, such as higher wages, safety, political freedom, and better schools. Chain migration occurs when migrants follow family or community networks already established in a destination. Step migration means moving in stages, perhaps from village to city, then city to another country. Guest workers are migrants allowed to work temporarily. Transhumance is seasonal movement of livestock herders. While nomadism involves regular movement without a fixed home. Migration has major impacts. Sending countries may lose skilled workers in a brain drain, but gain money through remittances, funds migrants send home. Receiving countries may gain labor and innovation, but may also face housing shortages or infrastructure strain. Cities often grow through migration, increasing urbanization. Cultural diffusion spreads language, religion, food, and traditions. Governments may respond with border controls, guest worker programs, or refugee policies. The central themes of unit two are distribution, movement, demographic change, development, and human adaptation. Students should be able to interpret maps, population pyramids, charts, and case studies. Most importantly, they should explain how population growth and migration shape economies, cultures, politics, and the use of space around the world.