3-3: Human Population and the Environment
After this lecture you should be able to… Explain why human population growth is a central
concept in understanding environmental problems.
Identify factors that influence human population growth.
Analyze and describe the impacts of the demographics of a population on its environment.
Explain factors that determine the difference in human population growth patterns based on standard of living.
Population Dynamics
Popula'on dynamics is the general study of how popula'ons change.
A popula'on is a group of individual of the same species, living in the same area and/or that are interbreeding and sharing gene'c informa'on.
Demography refers to the sta's'cal study of human popula'on.
Demographers analyze popula'ons based on:
Abundance
Birth Rate
Death Rate
Growth Rate
Age Structure Includes Life Expectancy/
Longevity
Demographic Terminology
Crude Birth Rate Crude Fer'lity Rate Total Fer'lity Rate Age-‐Specific Birth Rate
Crude Death Rate Morbidity Incidence (per 100) Prevalence Cause Specific Death Rate
Specific Cause/10,000
Crude Infant Mortality Rate
Crude Growth Rate Rate of Natural Increase Doubling Time
Life Expectancy At Birth Life Expectancy Gross Na'onal Product
Per capita
NOTE: “Crude” numbers are measured per 1000 individuals.
NOTE: “Total” number are measured for the popula'on as a whole.
The History of Human Population Growth
There are dis'nct periods of growth/change in the history of the human popula'on. Hunter/Gather (< a few million) Rise of Agriculture
Popula'on density increase = popula'on growth
The Plague Decrease in concentrated
popula'on in Europe.
Industrial Revolu'on Improvements in health and
food supply Today (6.7 Billion in 2008)
Growth slowed in industrialized areas, but same historical pa]erns emerge in developing regions
Human Population as Exponential Growth Curve
The human popula'on (globally) con'nues to grow exponen'ally, but sub-‐popula'ons do not all increase at the same rate.
GROWTH RATE EXAMPLES: United States= 0.6%
Doubling Time = 117 years
Northern Europe = 0.2% Doubling Time = 350 years
Nicaragua = 2.0% Doubling Time = 26 years
Human Population as Logistic Growth Curve
Earth provides all the resources needed for the human popula'on to survive.
The resources are not unlimited and resource reduc'on can have an impact on popula'on growth.
Data indicates that while the human popula'on con'nues to grow (flow), it is doing so at a slower rate (flux).
Inflec&on Point
Age Structure
Popula'on growth curves show only popula'on size, and ignore factors that affect different segments of the same popula'on.
Disease, food/water availability, social, economic, and many other factors have a dispropor'onate effect on some age groups
Age Structure graphs show the distribu'on of ages within a popula'on.
Influential Factors on Human Demographic Transition
Resource Limita'ons As resources run out,
popula'ons are forced to reduce growth rates.
EXAMPLE of Posi've Feedback: increased popula'on increased starva'on increased death rate.
EXAMPLE of Nega've Feedback: Decrease popula'on increased resource availability increased survival.
Improved Technologies As we have developed new
technologies we have increased or ability to adapt to certain condi'ons.
EXAMPLE of Posi've Feedback: increased popula'on increase disease incidence decrease in drug availability increase morbidity
EXAMPLE of Nega've Feedback: increase medical treatment decrease disease incidence increase longevity decrease birth rate.
Life Expectancy (Longevity)
Maximum life'me is defined as the maximum possible age of a member of a popula'on.
Life expectancy is the average number of years an individual can expect to live.
Different demographic factors play a role in determining the life expectancy of an individual.
Compare to Average Residence Time!
Population Size vs. Environmental Impact
To determine the effect the size of a popula'on has on its environment, simply mul'ple the size of the popula'on by its measureable impact.
The measureable impact must include not only the ini'al impact of each individual, but also the dura'on of the impact.
As popula'ons evolve, the resources they used and the amount they use change.
Addi'onally, the results of using certain resources can generate new, even unexpected impacts EXAMPLE: CFC’s from aerosols, refrigerators, and air condi'oners.
T = P X I
Human Carrying Capacity
The human popula'on, while the most innova've and adaptable species on the planet, is s'll subject to environmental pressures.
Human carrying capacity will be ul'mately be determined by the impact that the human popula'on has in the environment. Short-‐Term Factors: distribu'on of food Intermediate-‐Term Factors: environmental altera'on, resource
availability, technology distribu'on. Long-‐Term Factors: soil erosion, decline in ground water supply,
decrease in low profile/high need supplies (water, land).
End of Lecture Objectives
Explain why human population growth is a central concept in understanding environmental problems.
Identify factors that influence human population growth.
Analyze and describe the impacts of the demographics of a population on its environment.
Explain factors that determine the difference in human population growth patterns based on standard of living.