8.1 Human populations

• Births and immigration

• Crude birth rate, immigration rate

• Deaths and emigration are outputs from a human population

• Crude death rate (number of deaths per 1,000 people in a population per year) and emigration rate (number of emigrants per 1

• The rates can be used at a variety of scales—from small urban areas, like a town, to a country to a region or to the global population

• Population dynamics can be quantified and analysed by calculating total fertility rate, life expectancy, doubling time and natural increase

• Total fertility rate is the average number of births per woman of childbearing age

• Life expectancy is the average number of years that a person can be expected to live, usually from birth, if demographic factors remain unchanged

• Doubling time is the number of years it would take a population to double its size at its current growth rate; it can be calculated by using the rule of 70

• The global human population has followed a rapid growth curve

• Models are used to predict the growth of the future global human population

• UN projection models indicate three scenarios linked to future fertility rates

• There is uncertainty about how future human fertility rates may change, leading to the three scenarios in the models

• Population and migration policies can be employed to directly manage growth rates of human populations

• These may be anti-natalist or pro-natalist, thereby directly addressing birth rates, or they may address immigration and emigration

• These policies may use a variety of cultural, religious, economic, social and political factors to achieve their aims

• Include: named examples

• Human population growth can also be managed indirectly through economic, social, health, development and other policies that have an impact on births, deaths or migration

• Many development policies addressing areas such as, but not limited to, gender equality, education, improvements in public health and welfare will indirectly affect births

• Include: two named examples

• The composition of human populations can be modelled and compared using age–sex pyramids

• The pyramid is measured in absolute numbers or as a percentage of the total population

• It shows the proportion of the population of either gender in each age group

• DTM describes changing birth and death rates through stages of development

• Used to analyse population change over time

• Increased stress on Earth's systems

• Related to biocapacity disparity and planetary boundaries

• Determine dependency ratio and population momentum

• Dependency ratio: dependent ages vs. productive ages (15-64)

• Population momentum: growth continues despite fertility decline

• Compare countries in different DTM stages

• Historical, cultural, religious, economic, social, political factors

• Climate change, drought, land degradation

• Sudden onset: flooding, fires, storms

• Slow onset: desertification, sea-level rise, saltwater inundation