Carrying Capacity and the Human Population

Understanding Human Population Growth• The earliest census in the 17th century

estimated human population at 680 million• At that point growth was slow, but then it

began to grow more rapidly and the doubling rate sped up• Time required for the population to double• Why?

Understanding Human Population Growth

Understanding Human Population Growth

Understanding Human Population Growth• Growth rate peaked in the 1960’s at

2.06%• Now is about 1.04%• Growth occurs because crude birth rate

exceeds crude death rate• Crude: based out of 1,000 and are not

adjusted for reproductive age structure• More importantly growth occurs because

the death rate is dropping faster than the birth rate

The Patterns of Births and Deaths• Crude death drops due to:

• Sanitation• Clean water• Readily available nutrition• Clothing • Shelter• Medical advances• Vaccination• Antibiotics• Other treatments

The Patterns of Births and Deaths• Birth rates decline less rapidly• Due to:• Economics• Culture• Politics• Religion

The Patterns of Births and Deaths• Birthrate is also impacted by how many

women are their reproductive years• Total fertility rate (TFR)• Average number of children a woman will

bear over her lifetime• Replacement level fertility• Total fertility rate at which a population

remains constant

The Patterns of Births and Deaths

The Patterns of Births and Deaths• Fertility rates are affected by several

factors• Accessibility to contraception• Education of women• Employment opportunities for women• Costs to raise children • Infant mortality rates• Affluence

Age Structure and Population Momentum• Population growth is also impacted by the

distribution of the population in • Age classes• Number of males and females in an age

group• Age structure• Distribution of population among age classes

Age Structure and Population Momentum• Best understood by looking at population

histograms• Diagrams that represent the number of

males and females in various age groups

Age Structure and Population Momentum• Population momentum• Built-in potential

for population growth due to a large number of individuals entering reproductive age

Age Structure and Population Momentum• Slow or no growth• Baby boomers• People born

in the US between 1946-1964

Age Structure and Population Momentum• Decline

Age Structure and Population Momentum• Each type presents challenges based on

the age-dependency ratio• (number of people under 15 + number of people over

65)number of people between 15 and 65

• Ages 15-60 hold jobs, pay taxes and support others• Higher ratios indicate an aging population• What is that challenge?

Modifying the Idea of Carrying Capacity for People• Does CC apply to the human population?• How do we modify it?

The Malthusian Dilemma• Thomas Mathus wrote Essay on

Population• Described that the environment will limit

human population growth• Has that happened?• Why not?

The Maximum Number of Individuals and the Demographic Transition• Difficult to have accurate CC for human

population• Countries use resources at various rates

and for nonessential purposes

The Maximum Number of Individuals and the Demographic Transition• Demographic transition• Process of moving from high birthrates and

death rates to high birthrates and low death rates to finally low birthrates and deathrates

The Maximum Number of Individuals and the Demographic Transition• Demographic transition• What factors impact a population to go

through this?

A Given Area of the Environment• Humans have modified their environment

to ensure survival• Could we survive as hunters and

gatherers?• What is the major modification that has

allowed our population to continue to grow?• Agriculture• Expanding into unused areas

Maintained Indefinitely• Sustainable development• Economic activities that meet the needs of the present

without compromising the ability of the future to meet their needs• Strong sustainability• Criterion that prohibits human actions degrading the

environment or using environmental goods/services faster than they are generated by the environment

• Weak sustainability• Principle that actions that degrade the environment or use a

natural resource or a waste-processing service faster than it can be generated can be sustainable if these losses are offset by an increase in either economic capital or social institutions • Which one do you think is best?

Identifying the Notion of Limits in Environmental Debates• Cannot look at only the environment, we

must also look at economics• Two views• Resource pessimist• Resource optimists

Identifying the Notion of Limits in Environmental Debates• Resource pessimist

Identifying the Notion of Limits in Environmental Debates• Resource optimists

Identifying the Notion of Limits in Environmental Debates• The answers aren’t easy and can be

debated from both sides• Spend a moment reflecting on your own

perspective