ISSUES
: Our Changing Population
Chapter 2: Global population issues
25
Can the Earth feed 11 billion people?
Four reasons to fear a Malthusian future
An article from
The Conversation
.
By James Dyke, Lecturer in Complex Systems Simulation, University of Southampton
H
umanity is on course for a population greater
than 11 billion by the end of this century,
according to the latest analysis from the UN’s
population division.
In a simple sense, population is the root cause of all
sustainability issues. Clearly if there were no humans
there would be no human impacts. Assuming you don’t
wish to see the complete end of the human race – a
desire that is shared by some deep green thinkers and
Bond super-villians – then the issue is whether there is
an optimal number of humans on the planet.
Discussions on population growth often start with
the work of Rev. Thomas Robert Malthus whose
An
Essay on the Principle of Population
published at the
end of the 18th century is one of the seminal works of
demography. Populations change in response to three
driving factors: fertility – how many people are born;
mortality – how many people die; and migration – how
many people leave or enter the population.
Malthus observed that more births than deaths would
lead to exponential growth which would always outpace
any improvements in farming and increases in yields.
Consequently, unchecked growth was doomed to end
in famine and population collapse. Malthus was right
about exponential growth, but he was famously wrong
about his dire predictions for the consequences of such
growth.
At a global level we can ignore migration (no
interplanetary migration happening just yet) and so the
tremendous rise in the total numbers of humans is a
result of an imbalance between fertility and mortality
rates.
Over longer timescales, the recent increases look
practically vertiginous. We seem to be on a trajectory
that would surely exceed whatever the carrying capacity
of the Earth is. However, 11 billion could be the high
water mark as the UN forecasts population to slowly
decrease after the end of this century.
This brings us to Malthus’ first error: he wasn’t able
to appreciate that the process of industrialisation and
development that decreased mortality rates would, in
time, decrease fertility rates too. Higher living standards
associated with better education, in particular female
education and empowerment, seem to lead to smaller
family sizes – a demographic transition that has played
out with some variations across most of the countries
around the world.
This may explain how populations can overcome
unsustainable growth, but it still seems remarkable
that the Earth can provide for a 700% increase in the
numbers of humans over the span of less than a few
centuries. This was Malthus’s second error. He simply
couldn’t conceive of the tremendous increases in yields
that industrialisation produced.
How we fed seven billion
The ‘green revolution’ that produced a four-fold increase
in global food productivity since the middle of the 20th
century relied on irrigation, pesticides and fertilisers.
You may describe yourself as an omnivore, vegetarian,
or vegan – but in a sense we all eat fossilised carbon.
This is because most fertiliser is produced through the
Haber process which creates ammonia (a fertiliser) by
reacting atmospheric nitrogen with hydrogen under
