© 2010 pearson education canada lecture 4: human population dynamics outline: ecology –...

© 2010 Pearson Education Canada

Lecture 4: Human Population Dynamics

Outline:

•Ecology – Population Dynamics

•Human Population Demographics

Live Estimate of Human Population:http://www.worldometers.info/world-population/


Learning Outcomes:

• At the end of this week, you should be able to:

• Describe logistic growth, carrying capacity, limiting factors, and other fundamental concepts in ecology

• Assess the scope and historical patterns of human population growth

• Evaluate how human population, affluence, culture and technology affect the environment

• Explain the fundamental concepts of demography and outline the concept of demographic transition

• Characterize the dimensions of the HIV/AIDS pandemic and its impacts on population, the environment, and sustainability

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Population characteristics

• All populations show characteristics that help scientists predict their future dynamics

• Population size = the number of individual organisms present at a given time

- Numbers can increase, decrease, or remain the same

• Population density = the number of individuals within a population per unit area

- High densities make it easier to find mates, but increase competition, and vulnerability to predation

- Low densities make it harder to find mates, but individuals enjoy plentiful resources and space

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• Sex ratio = proportion of males to females

• Age Structure = the relative numbers of organisms of each age within a population

- Age structure diagrams (pyramids)

Population characteristics

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Birth and death rates

- Type I: More deaths at older ages

- Type II: Equal number of deaths at all ages

- Type III: More deaths at young ages

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• Crude birth/death rates = rates per 1000 individuals

• Survivorship curves = the likelihood of death varies with age


Populations may grow, shrink, or remain stable• Natality = births within the population

• Mortality = deaths within the population

• Immigration = arrival of individuals from outside the population

• Emigration = departure of individuals from the population

• Growth rate = (Crude birth rate + immigration rate) - (Crude death rate + emigration rate)

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Unregulated populations

• Steady growth rates cause exponential population growth

- Something increases by a fixed percent

- Graphed as a J-shaped curve

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• Exponential growth cannot be sustained indefinitely

- It occurs in nature with a small population and ideal conditions


Limiting factors restrain growth

• Limiting factors = physical, chemical and biological characteristics that restrain population growth

- Water, space, food, predators, and disease

• Environmental resistance = All limiting factors taken together

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Carrying capacity

• Carrying capacity = the maximum population size of a species that its environment can sustain

- An S-shaped logistic growth curve

- Limiting factors slow and stop exponential growth

• Carrying capacity changes

Humans have raised their carrying capacity by decreasing the carrying capacity for other species

FIGURE 3.15

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The influence of some factors depends on population density

• Density-dependent factors = limiting factors whose influence is affected by population density

- Increased risk of predation, competition for mates, and disease occurs with increased density

• Density-independent factors = limiting factors whose influence is not affected by population density

- Events such as floods, fires, and landslides

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Human Population distribution

FIGURE 6.9

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Human Dispersal and AdaptationBiologically, humans are only suited to warm climates, temperatures > 20oC.

Historically confined to tropical wet and tropical wet/dry climates, 30% of land.


Human Dispersal and AdaptationHuman diffusion out of Africa required adaptation:•cultural adaptation, hunting, gathering and shelter.


Human Dispersal and AdaptationMost diffusion took place between 40,000 and 10,000 years ago.

20,000 years ago


Human Dispersal and AdaptationUntil ~12,000 years ago, human populations were very small and had little impact on the environment.

People lived in small mobile groups and survived by hunting and gathering.


The Rise of Human PopulationsAgriculture: allowed for higher rate of food production.

•Humans were able to settle and support larger populations. •Led to cleared land, soil erosion, water diversion and pollution.


The Rise of Human PopulationsGlobal Power Centres:•1500-1800: England, France and Spain.

•Established global trade routes that gave rise to modern industrial economies and consumerism.


The Rise of Human PopulationsGlobal Power Centres:•1900s: Europe and North America

•Relied on exploitation of resources.

Original Forest Cover


The Rise of Human PopulationsGlobal Power Centres:•1900s: Europe and North America

•Relied on exploitation of resources.

Current Forest Cover


The Rise of Human PopulationsGlobal Power Centres:•Exploitation has lead to vast waste pollution, air pollution and soil degradation.


Human population: 7 billion by 2013• It took all of human history to reach 1 billion

• In 1930, 130 years later, we reached 2 billion, and added the most recent billion in 12 years

FIGURE 6.26-21


Human population: 7 billion by 2013

FIGURE 6.26-22


Population Patterns and TrendsWhy are we spread unevenly across the continents?

People per km2


Population Patterns and TrendsTemporal and Spatial Variations in Population:

Physical environment: 60% of all land is unfavorable.•Dry lands•Cold lands•Mountains•Wet tropics



Physical environment: 60% of all land is unfavorable.

Human modification of the environment: irrigation …



Today: population movement is mainly due to economic hardship, political unrest and war.


Population Patterns and TrendsInternational Comparisons of Population Size and Density:

Relative Population Size


Population Patterns and TrendsInternational Comparisons of Population Size:

Source: Wikipedia “World Population”



Population Density: number of people divided by land area.

People per km2



Physiologic Density: number of people divided by area of cropland. Reflects intensity of agriculture in developing countries.


Population Patterns and TrendsVariations in Population Density Patterns:

In industrialized countries, 80% of people live in cities.

1 to <10

>=50

0.4 to <1

Sparsely populated

10 to <50


Population Patterns and TrendsMechanisms responsible for temporal and spatial population changes:

• Birth rates• Death rates• Migration

• Migration between countries has become less import but migration within countries is still significant.


Population Patterns and TrendsNatural population changes:

Crude birth rate: number of yearly births per 1000 people.

Crude death rate: number of yearly deaths per 1000 people.

Annual Growth

2.4%

1.6%

1.3%

1.1%

0.6%

0.6%

-0.2%

Birth rate

Death rate


Rates of growth vary with region

• At today’s 2.1% annual growth rate, the population will double in 33 years

• If China’s rate had continued at 2.8%, it would have had 2 billion people in 2004.

FIGURE 6.36-34


Population Patterns and Trends

Natural population changes:

Life expectancy: average age at death.


Population Patterns and Trends

Natural population changes:

Infant mortality: deaths per 1000 live births.


Break Time!


BUT, population growth is seen as a temporary phenomenon

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Movie (~58 mins)“Don’t Panic: Facts about Population”

• Data current to 2013

• Hans Rosling – M.D., statistician, academic, founder of Gapminder Foundation

• Take notes on the main points and graphs he makes

• Documentary film credits/info: http://www.gapminder.org/videos/dont-panic-the-facts-about-population/

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https://www.youtube.com/watch?v=FACK2knC08E


The demographic transition

• Demographic transition = a model of economic and cultural change to explain the declining death and birth rates in industrializing nations

• high birth and death rates change to low birth and death rates

• As mortality decreases, there is less need for large families

- Parents invest in quality of life

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The demographic transition’s four stages

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Population size


Is the demographic transition universal?

• It has occurred in Europe, U.S., Canada, Japan, and other nations over the past 200-300 years

• But, it may or may not apply to all developing nations

• The transition could fail in cultures that

- Place greater value on childbirth

- Grant women fewer freedoms

For people to attain the material standard of living of North Americans, we would need the natural resources of four and a half more Earths

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Age structure affects future population dynamics• Having many individuals in young age groups

results in high reproduction and rapid population growth

FIGURE 6.10

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Total fertility rate influences population growth

• Total fertility rate (TFR) = average number of children born per female member of a population during her lifetime

- Developed = 1.5

- Developing = 3.1

- Africa = 5.2

• Replacement fertility = the TFR that keeps the size of a population stable

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Factors affecting total fertility rate

• Increasing urbanization decreases TFR

- Children go to school, and increase costs

• With social security, elderly parents need fewer children to support them

• Greater education allows women to enter the labor force, with less emphasis on child rearing

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Female literacy is associated with birth rates

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• Poorer societies have higher growth rates than wealthier societies

- Consistent with the demographic transition theory

- They have higher fertility and growth rates, with lower contraceptive use

• 99% of the next billion people added will be born in poor, less developed regions that are least able to support them

• Poverty often results in environmental degradation (e.g. soil degradation, hunting of large mammals)

Poverty is strongly correlated with population growth

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The wealth gap and population growth contribute to conflict

FIGURE 6.19

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Population growth affects the environment

• The IPAT model: I = P x A x T x S

- (I) Our total impact on the environment results from the interaction of:

- (P) Population = individuals need space and resources

- (A) Affluence = greater per capita resource use

- (T) Technology = increased exploitation of resources

- (S) Sensitivity = how sensitive an area is to human pressure

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Population distribution• Humans are unevenly distributed around the globe

- Unpopulated areas tend to be environmentally sensitive (high S value in the IPAT equation)

FIGURE 6.9

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Summary• The human population is larger than at any time in the past

• However, the rate of growth has decreased because of:

- Demographics

- Better rights for women

• How will the population stop rising?

- demographic transitions

- governmental intervention

- disease

- social conflict

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QUESTION: ReviewWhat has accounted for the majority of the world’s population growth in recent years?

a) Women are having more babies

b) Death rates have dropped due to technology, medicine, and food

c) More women are using contraceptives

d) Nothing, the population has dropped in recent years

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QUESTION: Review

According to the I = P x A x T formula, what would happen if China’s 1 billion people had a lifestyle like Canadians?

a) Their population would automatically drop

b) Their population would automatically increase

c) Their affluence and technology would increase

d) Their impact on the environment would even out

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QUESTION: Review

How have humans been able to raise the environment’s carrying capacity for our species?

a) Through technology

b) By eliminating limiting factors

c) Through increased consumption

d) Spending more money on non-essential resources

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QUESTION: Review

Areas that lack significant numbers of people, and have a low population density are…

a) No longer available

b) Best able to support higher densities of people

c) Sensitive areas least able to support high densities of people

d) Located around tropical and grassland areas

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QUESTION: ReviewDescribe the relationship between growth rates and population size.

a) Falling growth rates automatically mean a smaller population

b) Falling growth rates automatically mean a larger population

c) Falling growth rates means we no longer have a population problem

d) Falling growth rates does not mean a smaller population, but that rates of increase are slowing

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QUESTION: Weighing the Issues

Would you rather live in a country with a larger population or smaller population?

a) Small population, so there will be more resources for me

b) Small population, so there will be more resources for others, including wildlife

c) Large population, so I can find a date

d) Large population, because people are our biggest resource

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QUESTION: Interpreting Graphs and Data

a) High birth and death rates rise cause population increases

b) High birth and death rates, but population is stable

c) High birth rates with low death rates cause population to increase

d) Low birth and death rates cause the population to decrease

What happens during the “pre-industrial” stage of the demographic transition?

FIGURE 6.14

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QUESTION: Interpreting Graphs and Data

According to this age pyramid, Madagascar’s future population will be…?

a) Balancedb) Largerc) Much largerd) Smallere) Much smaller

FIGURE 6.10

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QUESTION: Interpreting Graphs and DataAccording to these graphs, which countries had access to family planning?

a) Iraq and Pakistanb) Malawi and Haitic) Malawi and Kenyad) Kenya and Bangladesh

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© 2010 pearson education canada lecture 4: human population dynamics outline: ecology –...

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