Human population Ecology

Ch 5.

Human Population

How has human population grown?Slowly over time

Scarce food and incurable diseaseDeath rate highFamilies had many childern

500 years agoRaid growthWhy?

Agriculture, industrial; revolution, better food supply, shipping methods improved, improved sanitation, healthcare, improved medicine

Led to expanded human growth

Science Behind Human PopulationThomas Malthus

English EconomistHuman population cannont grow

exponentiallyLimits: Famine, disease, war

DemographyScientific study of human populationStudy a variety of social and economic

factors that effect human populationExamines characteristics of human

population and attempts to explain how and why human population changes over time

Things that help predict different population growth ratesBirth rate Death rateAge structure

HypothesisThese countries have completed a

“demographic transition”, a dramatic change in birth and death ratesHistorically: humans have high birth and

death ratesNow: High birth rate and LOW death rate

Because of better conditions of living

Demographic TransitionDramatic change in birth rates and death ratesLow Death rate, High Birth rate

From 1760 to 1910Society modernizes

Increase level of educationRaise standars of livingFamilies have fewer children

Birth rate decreasesPopulation growth slowsDemographic transition complete when:

Birth rate falls to meet death rate and population growth stops

Only complete in a few countries India and China high birth rate

Age StructurePopulation depends partly on how many

people of different ages make up a population

Age-structure diagramsPopulation profiles used to predict future

population growthShow population of a country broken down

by gender and age group

Age structure in USEqual # of people in each age groupSlow and steady growth rate for near future

Age Structure in Nigeria

• More young children than teenagers• More teenagers than adults• Population will double in 30 years

Controlling Human PopulationIndia

Compulsory sterilizationChina

Family planning programBenefits and bonuses

Forced abortions

Predicting Future Population GrowthMany factors

Age structure of countriesPrevalence of life threatening diseases

By 20509 billionGrowth will level off or decrease if countries

growing rapidly go through demographic transition

Lower growth rate means population growth is slowing by it is STILL growing

How does this effect environment?Ecologists predict that if this growth does not

slow even more there will be Serious damage to EnvironmentGlobal economy

Other ecologists predict that science, technology, and changes in society will control those negative impacts on economy and environment