Populations
Objectives
•To define important terms
•To identify impacts of a large human population
•To relate problems to human populations
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Population growth
There are approximately 6.9 billion people in the world and
over 80 million babies are born per year – that is almost
three babies per second!
The human population is said to be growing exponentially.
This means that the larger the population, the faster it grows.
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Exponential growth
An increase in average life expectancy is largely responsible
for the rapid increase in population. Why do people live longer
than they did hundreds of years ago?
⚫ better healthcare (hospitals, medicines, vaccines)
⚫ more and better food
⚫ cleaner water
⚫ better sanitation.
The biggest increase in population is in economically
developing nations, rather than economically developed
nations. Why do you think this is the case?
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The changing population
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The changing population
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The changing population
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The changing population
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The changing population
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Human populations
• Identify the reasons for the increase in life
expectancy
• Compare the shape of the graphs in
economically developed and economically
developing countries
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The human population
There are currently more than 6 billion people on Earth.
population (billions)
The human population has
grown exponentially since
the industrial revolution
when new technology
increased the carrying
capacity of the Earth.
The population growth rate can be calculated by subtracting
death rate from birth rate, or using the following equation:
population at population at
population –
= end of period start of period × 100
growth rate
population at start of period
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Demography
Demography is the study of the size and structure of
populations, including a population’s age and sex distribution.
Demographic rates, such as population growth rate, birth
rate and death rate can be used to describe how a population,
or a subset of a population, changes over time.
births deaths
population
immigration
emigration
A population’s demographic rates are determined by the
environmental conditions. Human populations are greatly
affected by their level of economic development.
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Ecosystem services
Ecosystems provide clean air, water, soil,
minerals, plants, animals, etc. on which
humans depend. These factors are
called ecosystem services.
Sustainability is important to ensure
that the needs of the present are met
without affecting the ecosystem
services for future generations.
However, the growth in population is putting more pressure
on our natural resources. When plants, water, fuel, etc. are
consumed more quickly than they are replaced, this leads to
environmental degradation and a loss of biodiversity.
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Sustainability
Humans will always need resources.
Our use of resources can be
sustainable or unsustainable.
Sustainable practices can continue
year after year without depleting the
resources for future generations.
However, the unsustainable use
of resources could lead to
environmental degradation, where:
⚫ resources are depleted
⚫ habitats are destroyed
⚫ the levels of pollution increase.
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More people use more resources
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More people use more resources
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More people use more resources
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More people use more resources
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Growth rate and food security
The population growth rate has an impact on the global
food security. With more people to feed, the likelihood of
food shortages will increase.
In natural ecosystems, all of the
energy in food (plants and
animals) comes from the Sun.
Moving up each stage in the
food chain, less material and
less energy are contained in the
biomass of the organisms.
One way to increase the efficiency of food production is
to reduce the number of stages in food chains.
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Deforestation
The removal of forest habitats to make
use of the land is called deforestation.
Harvesting the timber, and replacing
vegetation with agricultural crops and
livestock, can have damaging effects
on the ecosystem.
⚫ Burning timber releases carbon
dioxide into the atmosphere.
⚫ Forest habitats are lost, leading
to a reduction in biodiversity.
⚫ The level of photosynthesis is
reduced, meaning less carbon
dioxide is used up in this process.
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Deforestation
The destruction of a woodland habitat may mean species
are unable to find the resources they need to survive.
They may become endangered or even extinct.
In Borneo, the orangutan population is slowly declining as
forests are slowly being removed to make way for other crops.
1950 1985 2000 2005
In some areas, woodland is cleared to grow crops that can
be used to produce biofuels.
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What are pollutants?
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What are pollutants?
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What are pollutants?
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What are pollutants?
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What are pollutants?
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What are pollutants?
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What are pollutants?
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What are pollutants?
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Land pollution
Land and soil can be polluted by two main types of
substance:
⚫ solid waste – such as plastic,
metal, paper and other man-
made substances
⚫ chemicals – such as
herbicides and pesticides,
crude oil and waste from
industrial processes.
Land pollution often leads to
water pollution, as chemicals are
washed into rivers and lakes.
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Water pollution
Sewage, industrial waste, oil, pesticides and fertilizers all
pollute water.
Fertilizers and sewage can easily be washed into rivers,
streams and lakes. The nutrients, phosphates and nitrates in
these substances cause eutrophication.
Eutrophication is the
accumulation of nutrients
in water, which causes
excessive algal growth.
This leads to a reduction
in oxygen levels and the
death of aquatic life.
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Air pollution
Human activity produces two
main types of air pollutant:
⚫ noxious gases, i.e. carbon dioxide
(CO2), sulfur dioxide (SO2) and
nitrogen oxides (NOx)
⚫ particulates, which are tiny
particles suspended in air.
Air pollution is increasing with population growth because:
⚫ the burning of fossil fuels increases to provide more energy
⚫ an increase in rice and cattle farming to supply more food
generates methane, which is 7.5 times more effective as a
greenhouse gas than carbon dioxide.
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Who uses the most energy?
This map shows world energy consumption per capita.
Do countries that are more or less economically developed
use the most energy?
kg of oil
equivalent
Over 10,000
5,001 to 10,000
2,501 to 5,000
1,001 to 2,500
501 to 1,000
0 to 500
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Who produces the most CO2 emissions?
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Who produces the most CO2 emissions?
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Global warming and greenhouse gases
One of the greatest threats caused by air pollution is
global warming. Global warming is caused by a build-up
of greenhouses gases, which leads to an increase in the
Earth’s temperature.
A greenhouse gas is an atmospheric
gas that absorbs infrared light.
Key greenhouses gases include:
⚫ carbon dioxide (CO2)
⚫ methane (CH4)
⚫ water vapour (H2O)
⚫ nitrous oxide (N2O).
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The greenhouse effect
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The greenhouse effect
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The greenhouse effect
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The greenhouse effect
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The greenhouse effect
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The greenhouse effect
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