Human Population: Approaching 7 Billion
Nation population continue to grow, we are at 6.7 billion
o China working to slow population growth
o The rate of global growth is slowing
The Human Population is growing nearly as fast as ever
Population increases as a quantity by a fixed percentage
per unit time, like a compound interest accrues（积累）
in a savings account.
o A given percentage of a larger number is > than an
equal percentage for a small number
Population growth hasn’t remained steady
o Vary greatly from region to region
China instituted its one child population, as its growth was
o 2.8% = 25 years doubling time of population.
Perspectives （远景）on human population have changed
In the 1700s population growth was regarded as a good
o Parents thought of a high birth rate as more children
to support them at an old age
o For society, it meant a greater pool of labour for
Malthus (british economist) said the population growth
had to be limited by laws or social controls or the number Chapter 6
of people would outgrow（出生） the food supply until
starvation, war, or disease arose and reduced it.
o Published essay on the principle of population
Is population growth really ‘problem’ today?
The ongoing population growth has been made possible by
technological innovations, improved sanitation, better
medical care, increased agricultural output, and other
factors that have led to a decline in death rates,
particularly a drop in rates of infant mortality（死亡率）.
o Enormous increases in crop yields and advances in
agricultural technology associated with the Green
Births have outpaced（超过。。的速度） deaths for
many years now
o Creating population problem.
Cornucopian（丰富的） thinkers believe we can find a
way to replace depleted resources.（资源枯竭）
Not all resources can be replaced or reinvented（改造）
once they have been depleted
o Once species is extinct it is gone.
o We can’t expand earth like a balloon.
Resource availability must keep pace with population
o Otherwise in the future each person will have less
space to live, eat and material wealth
In todays world population growth is strongly correlated
with poverty than with wealth. Chapter 6
Outside of Europe 56% of national governments feel their
birth rates are too high, and only 8% feel they are too low
o In Europe 3 of every 5 European national
governments say their birth rates are too low
Global population growth and resulting environmental
scarcity have played a central role in causing famine,
disease and social & political conflict around the world.
Population is one of several factors that effect the
Impact is thought of in various ways
o Pollution or resource consumption
Increased population means more
individuals take up space, use natural
resources and generate waste
Increased affluence magnifies（放大）
environmental impact through the greater
per capita resource consumption that
generally has accompanied enhanced
May decrease or increase human impact on
the environment. Chapter 6
Can decrease impact if we reduce
smokestack emissions, harness
Increase if we enhance our abilities to
exploit minerals, fossil fuels, ocean
We can add a sensitivity factor (S) to the equation
Denote how sensitive given environment is
to human pressures
o Disturbance of regions may slow down
Technology advances to increase global agricultural
production faster than our population his risen.
China is a window on what much of the rest of the world
could soon become
o World’s developing countries try to attain the level of
material prosperity that industrialized nations enjoy.
The application of population ecology principles to the
study of statistical change in human populations is the
focus of the social science of demography
The environment has a carrying capacity for humans
Environmental factors set limits on our population growth,
and the environment has a carrying capacity for our
species. Chapter 6
4 Significant periods of societal change appear to have
fundamentally altered the human relationship with the
environment and increased the carrying capacity,
triggering remarkable increases in population size.
o Paleolithic period (stone age旧石器时代
Humans gained control of fire and began to use
stones as tools to modify the environment.
o Nomadic Hunter-Gatherer lifestyle (agricultural way
Agricultural Revolution (new stone
People began to grow their own crops, raise
domestic animals and live settled,
sedentary lives in villages, found it easier to
meet nutritional needs.
Lived longer and had more children who
survived to adulthood.
Began in mid 1700s
Shifted rural life, animal powered
agriculture and manufacturing by craftsmen
to an urban society powered by fossil fuels
Introduced improvements in sanitation and
Introduction of fossil fuel enhanced
o Powered equipment, steam engines,
and synthetic fertilizers. Chapter 6
We are in the midst of a fourth major transition
o Medical-Technological Revolution
Involving the globalization of modern medical
and technological advancements.
Marked by developments in medicine,
sanitation and pharmaceuticals
Hopefully this transition will BE MORE
SUSTAINABLE, RENEWABLE ENERGY
SOURCES AND away from dependence on
Demography is the study of human population
Demographic data helps us understand how differences in
population characteristics and related phenomena (e.g.
decisions about reproduction) affect human communities
and their environments.
Demographers study population size, density, distribution,
age structure, sex ratio, and rates of birth, death,
immigration, and emigration of humans, just as population
ecologists study these characteristics in other organisms.
The size of the population doesn`t tell a whole story
o A populations environmental impact depends on its
density, distribution, and composition, as well as on
affluence, technology level of consumption, and other
factors outlined earlier.
Population density and distribution Chapter 6
People are distributed very unevenly over the globe.
Population density is the number of people per unit of
o High in regions with temperate, subtropical, and
China, Europe, Mexico, Southern Africa, and
o Low in regions with extreme climate biomes
Desert, deep rainforest and tundra
o Dense along seacoasts and rivers
Less dense at locations far from water.
This means that certain areas bear far more environmental
impact than others.
Areas with low population density are often vulnerable to
o The reason they have low population in the first place
is because they are sensitive(S In IPAT) and cant
support many people.
Deserts have low availability of water.
o The artic tundra is another environment highly
sensitive to environmental change and human
Disturbance of vegetation (something as simple
of a set of car tracks) can cause deep melting of
permafrost and collapse of soil, the scars of
which may last for years or even decades.
Age structures Chapter 6
China guaranteed its population age structure would
change by causing dramatic chnges the number of children
o Shift in age structure as the number of people older
than 65 will rise from 100 million in 2005 to 236
million in 2030.
o Dramatic shift will challenge chinas economy, health
care systems, military forces because fewer working
age people ewill be available to support socil
programs that ssist the increasing number of older
Shift in age structure also reduces the proportion
of dependednt children.
Decrease in crime rate may occur because
of reduced number of young adults.
For every 100 female infants born, 105-106 male infants
o Men are slightly more prone to death making it equal
Women then predominate as the population
ages leading to a ratio of males to females that is
slightly less than one-to-one.
A greatly distorted ratio can lead to problems
but a slightly uneven is beneficial.
Lately, a male dominance in new born babies. (some
provinces are 138 boys for every 100 girls)
o Might be because females may abort foetuses after
learning the child`s sex from ultrasound. Chapter 6
China want to have their only kid a son so he
could carry on the family name.
This is the sex skewed ratio.
Population growth depends on rates of birth, death,
immigration and emigration.
Rates of birth, death, immigration, and emigration help
determine whether a human population grows, shrinks or
Crude Birth Rate & C