Simple population model
Here is an exercise for GSCE/A level/UG Geography students I developed for RIS (Researchers in Schools)
I like it because it speaks directly to students' futures.
- The UK is overpopulated in the sense that its current 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 generation 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 construct a simple stepwise forecast model starting at 1900 of the UK's population, GDP per capita and total ecological footprint on a spreadsheet. In it 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 GINI coefficient. Birth and death change the population of the next timestep, and GDP and ecological footprint is estimated from real/forecast 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
For example, provided there is
- imminent reduction in income disparity (down to current Scandinavian levels) - which boosts 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 - to avoid a slump in GDP per capita and an even bigger slump in population
the model trends suggest something like this:
So by about 2100, the UK would end up 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 reality.
