View source for Simple population model

Here is an exercise for GSCE/A level/UG Geography students I developed for RIS ([https://researchersinschools.org/ Researchers in Schools])

It concerns something called the [https://en.wikipedia.org/wiki/Demographic_transition demographic transition].

I like it because it speaks very directly to students' futures.

:''The UK is overpopulated in the sense that its current [https://wwf.panda.org/knowledge_hub/teacher_resources/webfieldtrips/ecological_balance/eco_footprint/ ecological footprint] is significantly larger than its ecological capacity. This means that its population is consuming more environmental resources than are actually available to it.  Are we all doomed?  Let's find out.''

====Exploring the Data====

The UK's current population represents a high water mark, and is due to go into (possibly steep) decline as its rapidly ageing population dies off over the next 20-30 years leaving diminished numbers of younger people with low birth rates in its wake.  Germany and Japan are already beginning this decline.  The US, Canada and Australia have been staving it off with mass immigration.  Much of the developing world is just one or two generations behind.  This reduction in birth rate is part of a natural transition related to "modernisation".  Coupled with it has been a pretty rapid reduction in environmental impact per unit of GDP production that’s been going on since the 1960's - at least in the developed world.

====Model & Validation====

Students use a spreadsheet to construct a simple stepwise forecast model of the UK's population, [[GDP per capita]] and total ecological footprint, starting at 1900 and lasting e.g. 300 years.  In it average people are born, have babies at a certain age and die at a certain age. Birth rates vary with GDP per capita modified by the [https://en.wikipedia.org/wiki/List_of_countries_by_income_equality GINI coefficient].  Birth and death change the population of subsequent timesteps, and GDP and ecological footprint respond via trends identified in data.  Immigration of people in their 20′s is included, a proportion of whom settle permanently and have children too.  All assumptions can be varied to investigate their impact and the model is validated against data from 1900 to the present.

====Results & Conclusions====

An obvious way through seems to be 
# imminent reduction in income disparity (down to current Scandinavian levels) - to boost GDP ''and'' birth rates
# the rapid convergence on today’s environmental state-of-the-art (also Scandinavian) continues - no new inventions necessary!
# increased short-term immigration - avoids an even bigger slump in population and a slump in GDP per capita
This gives trends that look like this:

[[File:Ukpop+ecofp.jpg]][[File:Ukgdppercap.jpg]]

So by about 2100, the UK could end up roughly ecologically sustainable with a stable population of about 40 million pretty mobile, well off people.  

Of course, everything depends on what students decide to do, in both the model and in life.
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