8.2 - population models, population momentum and environmental migrants

features of rapid growth age-sex pyramid

• poor healthcare

• short life expectancies

• usually in under developed countries

features of slow/stable growth age-sex pyramid

• good healthcare

• long life expectancies

• stable governments

• mostly in developed countries

features of negative/ declining growth age-sex pyramid

• good healthcare

• long life expectancy 

• stable governments

• lower than replacement rate births

• found in developed countries 

demographic transition model (DTM)

shows how population transitions from pre-industrial stage to an economical advanced stage

strengths of DTM model

• simple framework

• broad applicability

• helps predict future trends

weaknesses of DTM model

• assumes linear progression

• overlooks external factors

  • doesn’t account for migration, policies and global events

• stage 5 uncertainty

• ignores inequalities

  • differences urban vs rural

impacts of populations

• biocapacity deficit = cnsumption> regeneration

• greater greenhouse gas emission

• social and economic inequality

• increased risk of crossing planetary boundaries 

total dependency ratio

ratio of dependents (people typically not in the labor force) to the number of working-age individuals

• TDR = (14 > x > 64 population / working age population) x 100

importance of dependancy ratio

• allows for future economic, social and health needs prediction

• high ratio = high nr. of people dependant on working population

limitations of TDR

• many children under 14 work in LEDs

• age of retirement is very fluid

population momentum

continued population growth that occurs even after fertility rates decline

• due to large base of young people

• wide base = high momentum = future growth

environmental migration causes

• sudden onset events

• slow onset events

environmental migration impacts

• on livelihood

• on food security

• on habitat

environmental emergency migrants

temporary migrants

environmental forced migrants

leave areas due to environmental deterioration or degradation

environmental motivated migrants

avoid expected climate induced threats in the future