Topic 8 opens with the most basic question in environmental science: how many of us are there, and how quickly is that number changing? Everything that follows in this topic, the cities you will study in 8.2 and the air pollution in 8.3, rests on the answer.
You already know how to treat something as a system, with inputs, outputs and a storage between them. A human population works in exactly the same way. People are added, people are lost, and the size of the population at any moment is the balance between the two. What makes human populations interesting is that we can measure those flows precisely, for every country on Earth, and the numbers turn out to be wildly different from one place to another.
Today you will do that measuring yourself, using live data for two countries that could hardly be less alike.
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You are working on your own today.
Everything you need is on this page and on one website: Country Profiles.
Duplicate this page first, into your own ESS folder, and work on your copy.
Work through the four phases in order. They build on each other, so do not skip ahead.
Type your answers straight into your copy: there is a blank bullet under every question, and the tables have empty cells waiting for you.
Stuck on a calculation? Try it twice, then open the Check your answers toggle near the bottom of this page.
Site will not load, or no laptop? Open the If the site will not load toggle near the bottom. Everything you need is in there.
Hand in at the end of the period: your answer to the exit question in Phase 4.
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This is a data visualisation from the American Museum of Natural History. It plots human population as dots on a world map and runs a counter of the total, from early human history to the present day and on into projections.
The link starts you at 3 minutes 20 seconds, which is roughly where the counter begins to climb steeply. Watch from there to the end.
Have your copy of this page open while you watch. You will use these figures again in Phase 2.
https://www.youtube.com/watch?v=vJ5p3pZlBi4&t=200s
Task 0.1 Note these down as you watch.
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8.1.1 Births and immigration are inputs to a human population.
Crude birth rate (number of live births per 1,000 people in a population per year) and immigration rate (number of immigrants per 1,000 population per year) are the quantitative measures of population input. The rates can be used at a variety of scales—from small urban areas, like a town, to a country to a region or to the global population.
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8.1.2 Deaths and emigration are outputs from a human population.
Crude death rate (number of deaths per 1,000 people in a population per year) and emigration rate (number of emigrants per 1,000 population per year) are the quantitative measures of population output. The rates can be used at a variety of scales—from small urban areas, like a town, to a country to a region or to the global population.
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A population has two ways of gaining people and two ways of losing them. The population itself is the storage, and its size at any moment is the running balance of the flows in and the flows out.
All four are expressed per 1,000 people, which is what makes them comparable. Niger has roughly three times as many people as Switzerland, so comparing raw counts of births would tell you almost nothing. Rates strip the population size out and let you compare the intensity of each flow.
The word "crude" is a warning label. It means the rate takes no account of the structure of the population, only its total size. A country full of young adults and a country full of pensioners can have very different death rates for reasons that have nothing to do with how healthy either country is. You will come back to this in Phase 3.
One practical point before you start. The Country Profiles site reports net migration, a single figure in persons per year, rather than separate immigration and emigration rates. Net migration is the immigration input minus the emigration output. A positive figure means more people arriving than leaving; a negative figure means the reverse. It tells you the balance of the two flows, but it cannot tell you how large either flow is on its own.
Your two countries today are Niger and Switzerland. Open both profiles in separate tabs and leave them open, you will use them all lesson:
Niger · Switzerland
On each profile, click Changing population to expand it. Every figure you need today is in there.
Task 1.1 Fill in the table below from the two profiles. Record the year shown next to each figure.
| Indicator | Niger | Switzerland | Input, output or balance? |
|---|---|---|---|
| Total population | |||
| Crude birth rate (per 1,000) | |||
| Crude death rate (per 1,000) | |||
| Net migration (persons per year) |
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8.1.3 Population dynamics can be quantified and analysed by calculating total fertility rate, life expectancy, doubling time and natural increase.
Total fertility rate is the average number of births per woman of childbearing age. Life expectancy is the average number of years that a person can be expected to live, usually from birth, if demographic factors remain unchanged. Doubling time is the number of years it would take a population to double its size at its current growth rate; it can be calculated by using the rule of 70. To do this, divide 70 by the growth rate (as a percentage). Natural increase is birth rate minus death rate, expressed as a number per 1,000 or as a percentage (the birth rate minus the death rate is divided by 10).
Application of skills: Work out natural increase rates and doubling times from given data.
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