This course introduces the academic approach of Sustainability and explores how today’s human societies can endure in the face of global change, ecosystem degradation and resource limitations. The course focuses on key knowledge areas of sustainability theory and practice, including population, ecosystems, global change, energy, agriculture, water, environmental economics and policy, ethics, and cultural history. This subject is of vital importance, seeking as it does to uncover the principles of the long-term welfare of all the peoples of the planet. As sustainability is a cross-disciplinary field of study, this foundation requires intellectual breadth: as I describe it in the class text, understanding our motivations requires the humanities, measuring the challenges of sustainability requires knowledge of the sciences (both natural and social), and building solutions requires technical insight into systems (such as provided by engineering, planning, and management).
Future Populations, Part 2
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Из курса от партнера University of Illinois at Urbana-Champaign
Introduction to Sustainability
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Population
In this module, we will see how human populations have evolved over time and get a sense of where the next century of change will take us.
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Dr. Jonathan TomkinAssociate Director
School of Earth, Society and Environment
I am Jonathan Tomkin from the University of Illinois
So we have looked at the past of Japan and used
it to predict the future.
Let's look at some other countries around the world.
You know, I am going to show you some UN generated data sets
of the population periods for the countries in the different
stages in the demographic transition.
This is a very youthful pyramid
very youthful pyramids tend to be spread out at the base
So they are not exactly pyramid shape, a lot ike triangles
and these things are cases for there is lot of potential for the future population growth.
because there is lots of people who haven't entered the
fertility ages yet, those people below the age of 15.
So, Afghanistan which we have already discussed has a very high
fertility rate has displayed out structure at the base
here Male are show in blue and Female in yellow
and you can see
there is a very large group of people slightly lighter colors
which indicates the people who are just entering
the pre family builiding stage. So there is a lot of potential here for the
population to increase.
A more classic pyramid structure might be a place like the Phillipines.
Its still very youthful. We describe is as youthful population pyramid,
but in this case, the pyramid is not swayed at the base
its a little bit flatter
In fact you can actually see that the age groups of
0-4, 5-9 are actually pretty similar to one another.
So, This is suggesting that perhaps the Phillipines
is also entering a stage of demographic transition
Transitional countries and United States is a good example of that
still experience some population growth.
So They haven't gone through the whole demographic experience
of transition period to stage IV
The fertility rates are still higher than death rates.
But if you look at the younger age groups
you can see that there is that start of that fat structure
so you no longer have that wide period base, but instead as we
see in this example of Mexico that we
can see that the age groups between 0-5, 5-10 and upto 20 in this case
are very flattened stable, so this is suggesting that the future
is building towards one of those more stable
population where death rates and fertility rates are the same
Other countries have gone through this process
We looked at Japan, another good example is Germany
Germany has that wedge or cup shape, so we call
it mature country. These mature countries are
actually experiencing net population decreases.
Some countries like Germany might also experience
an immigration, which might balance that.
But if we look at this just in terms of fertility vs death rates
we can see that the population of future of Germany
will be lower than it is today.
because there are far less people in the pre-family
stage. There are far less people age between 0-20 than there
are in the older age groups. In particular, Here we see
that in Germany the biggest people are in the age group of forties.
These are the people who are leaving their family formation stage
are leaving that additional growth stage
So the thing to watch out for mature countries is
that the base of the pyramid is thinner and is not as wide as
for the older cohorts
So the demographers who use this to predict the future
This graph shows the yearly growth rate of the world
population vs the year. Historically, we can
see this being a big change. There is quite
a bit of variation early on, like just after 60's we
talked about the impact of cold war effects like
Gen X, Baby Boomers and so on. But nevertheless, the world population growth
today is about 1% and it is being historically trending down.
Based on what demographers know about world population
shapes, they expect this trend to nearly continue
Most this means that by about the mid-century
population growth will be about half of what
it is today. So the growth will be slowed
from 1% per year to about 1/2% per year
This is just the same as so many patterns we have
seen in the past. If you look at this graph
you can see that around 1980s i.e. around 30 years ago,
the world's population growth rate was almost double what is today
It was about 1.8% per year
So the world seems to be on the path to lower and lower
rates of yearly increase. This means,however. we will continue
to see more and more people on the earth
over the next few decades.
Note the fattening of this pyramid at this time.
This shows the world population pyramid providing 1950, 2010
and then projections for 2050 and end of the century 2100
So, in the begining 1950s, this was almost 60 years ago
we see a fairly classic shape. Its a wide based
and very pyramidal. The world today is actually in a transitional
shape, the base is quite fat but its also flat.
So In other words, the people who are being born today are
not very different from the number of people who
were born 10 years ago or 20 years ago.
But the population continues to increase
even though this base does not continue to get fatter
If we look at the world in 2050, the number of people
who are in age between 0-10 is about the same as today.
The reason why there are many more people is because
less people are dying.
So the reason we are seeing of this population growth rate
around the world today is not because there is going to be a jump
in number of people being born relative to today, its because
the people who are being born are going to live and are going to live for longer.
So in some ways, the world increase in population
is very hopeful theme because it indicates that
people lives are getting better, more secure and healthier.
The predictions are very difficult beyond 2050
because there could be lot of culture changes, there could be
technological changes. We have made very firm predictions that you will
see that United Nations has a range of ideas about what
the world population might be at the end of
this century.
But if the world population of developing countries
follows the same pattern as we saw in developed
countries, we would expect to see this transition
to more mature age structure and this means
we will get what we will see here in 2050 and 2100
where we have this very flat block shaped structure
where the world population is relatively stable
and the death rate is really have been abated until people reach
old age. So the sort of thing that killed people
in the past pandemics, communicable diseases, poor diet
and lack of nutrition are things that are being eliminated
and that's why people are living so much longer.
and if this is the case, we expect to see this flat
maturized structure.
So the UN then has several different world population
projections made depend on different presumptions.
You can read more about this from the readings.
But I'll tell you that the favorite model has
about century in population so
that is the number of people at the end of this century
of about 10 billion people
Don't forget there are 7 billion today.
So that's a fairly significant increase.
The other thing this favorite model which is
the orange line, if we look at this dataset we can see the
historical trend data going back is the black and
you have very good data in blue from the modern era
and the three different colors - red, yellow and green
are the different in-member scenarios
the United Nation looked out that the preferred model
yellow one - growth really becomes flat by mid-century and the end of the century
So we might see a popualtion of around 10 billion
by 2050 and then population might not change by end of
the century. So this suggests that if we look
at that yellow curve, which is their most favorite
curve, that we have an S shaped population growth pattern
So that's a stable population growth pattern which wouldn't
an opportunity to go through a crash, unless of course, we are
already be on the world's carrying capacity.
The red line assumes the population
doesn't follow the trend that we have seen in the past
that fertility rates go up rather than come down in
the countries. In this case we might see at one point 16 billion people
at the end of the century.
On the other hand, if the demographic transition is
more agressive, because we have this faster pace loss in the
21st century than we had at 20th cnetury or 19th,
Its possible that population will contunue forward.
This would imply that lot of countries would follow
path of Germany and Japan, having rich people with few kids
and under this scenario, we want to expect less
people at the end of the century than they
are today. Less than 7 billion. So there is a range of futures out there.
but if we look at this - The most favorite model, the most predictions
based on what we have observed so far over the last 100 years
would indicate that the population will slowly increase
and this population increase will be largerly due to
the extended life expectancies and not due to
explosions in the rates of births.
I have spoken a lot about population growth.
The one thing to be very aware of
and this is what all the demographers agree
that it is not going to be even everywhere.
Some countries will see significant population growth
and some countries will see no population growth and even an decline
Here we have data from 1950 and 2010 of the
biggest countries in the world.
so today as it was true in 1950, China has the highest
population (that's the red line).
and India has the second largest population.
Between 1950 and 2010, both these countries saw
enormous increase in number of people.
The third largest country is United States
which is also saw big increases in population.
and perhaps If you look at one of those countries who existed below
however, it is not expected that future population
growth will follow the same pattern.
Because a lot of these countries are going through demographic transitions.
India is expected to continue to see significant
population growth. because its yet to experience
this demographic transition.
China, on the other hand, has experienced a very
significant demographic transition. In fact the birth rates
in China today are below replacement rate.
so the world's most populous country is not expecting
to see large increases in the population of future.
If we look at other countries such as the United States
this transitional country, which has high immigration
we might see modest increases in the future
populations. And for lots of other countries on this list
you will see that these populations trends increase and some otherwise
significant countries such as Russia and Germany
will drop out of this list of the largest world population
because they don't see peak population growth and in fact,
for one of these countries we see decline is expected of this coming century
I like to point out that China is a very
good example of the county which is surprising
in that we think about as developing country
the culure of the pass through demographic transition
we expect the world population of China to be lower
at the end of the century than its today
Most of the world population growth between today
and end of the century is predicted to occur in
Africa. Let's look at this graph.
Africa sees a net population increase over the 90 years
between 2010-2100 of 2.5 billion. Other areas in the
world such as Latin America, North America
Asia will see increases. Some of these will be
relatively modest. Asia will see almost 1/2 billion increase
Other countries in places such as Europe in particular
will see decreases. So there actually will be
less people in Europe at the end of the century
than there are today based on the demographic
trends we spoke about in today's lecture.
Given that the people of Africa are much poorer than
most other places in the world - on average.
and so consume less. It might be, unless there is
a significant catchup economic growth, the impact of these
additional people will be on the world environment
will be lower than you might expect.
I will give you an example.
Let's look at Green House Gases.
Average Sub-Saharan African emits less than 1 ton of CO2 (Carbon Dioxide) each year
The average American emits over 20 tonnes per year
In the absence of significant economic change
in these countries, it implies that 192 additional
North Americans could have a much bigger impact
on global climate than 2.5 additional billion
Africans. So we have to be careful when we
think about predicting the future for the environmental impact
that these changes of population are. It could be
that rather than the population change having the
biggest impact on World's climate or other environmental
processes or other sustainability issues, it could be
standard of living that is the most of imporant
So we see increases in consumption to match these
increases in the population.
that's when we will see the need for new forms of energy, improvised
dealing with polluition such as CO2 in the atmosphere.
So population growth may not be the horror it could be
population growth rates are decreasing and they
are on track to stablize this century.
It might infact be that for environmental sustainability
consumption patterns have a much more bigger impact than
population change will.
There are some problems that are not resolving
themselves however. In the next week set of lectures,
we will talk about an entire class of problems
known as "Tragedy of the Commons" and this explains why
things such as global atmosphere, the world fisheries
or even the shared bathroom down the hall are not in state we might wish them to be
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