Human populations and urban systems practice questions.

A country records a crude birth rate of 34 per 1000, a crude death rate of 11 per 1000, and sanitation and food supply are improving rapidly. In the demographic transition model this country is in

• stage 1, where both rates are high and fluctuate from year to year
• stage 3, where birth rates fall while death rates remain low
• stage 2, where death rates have fallen but birth rates remain high
• stage 4, where both rates are low and the total population is close to stable

Answer: stage 2, where death rates have fallen but birth rates remain high

Stage 2 is defined by the death rate falling ahead of the birth rate, which opens the widest gap between the two curves and gives the fastest natural increase in the whole model. Stage 3 begins only once the birth rate itself starts to fall.

A high-income country has a total fertility rate of 1.4 and a life expectancy that continues to rise. The most likely demographic consequence over the following decades is

• an expansive pyramid with a very broad base of young children
• a rising old-age dependency ratio and a shrinking working-age population
• a natural increase rate that climbs steadily above two per cent per year without migration
• a fall in the mean age of the population as fertility continues to decline

Answer: a rising old-age dependency ratio and a shrinking working-age population

A total fertility rate of 1.4 is well below the replacement level of about 2.1, so each cohort reaching working age is smaller than the one retiring, while rising life expectancy adds people at the top of the pyramid. Falling fertility raises the mean age, it does not lower it.

A city has an ecological footprint of 5.2 gha per person, while the biologically productive land inside its own boundary amounts to 0.1 gha per person. This comparison shows that

• the city runs an ecological deficit and depends on productive land elsewhere
• the city has a biocapacity surplus that it exports to the surrounding region
• the footprint must have been measured in the wrong unit, since footprints are given in tonnes
• the city's per-capita resource use must be below the global average

Answer: the city runs an ecological deficit and depends on productive land elsewhere

The footprint is the area demanded to supply resources and absorb waste, while biocapacity is the area available; where demand exceeds local supply the shortfall is imported through trade and global sinks. The unit is always area (gha), never mass.

A government introduces extended paid parental leave, subsidised childcare and a cash payment on the birth of a third child. This set of measures is best classified as

• an anti-natalist policy, since the incentives discourage births
• an immigration policy, since it targets net migration rather than births
• a policy designed to lower the youth dependency ratio within a decade
• a pro-natalist policy, since the incentives encourage more births

Answer: a pro-natalist policy, since the incentives encourage more births

Pro-natalist policies use incentives to raise the total fertility rate; anti-natalist policies use disincentives or limits to lower it. In the short term extra births raise the youth dependency ratio rather than lower it, because the children are dependants for years before they join the workforce.

Across a wide range of countries, the change most consistently associated with a fall in the total fertility rate is

• an increase in national income spent on road infrastructure
• an increase in the level of female education and paid employment
• an increase in the crude death rate among the elderly population
• an increase in the proportion of the population living in rural areas

Answer: an increase in the level of female education and paid employment

Female education delays first births, raises the opportunity cost of leaving paid work and improves access to family planning, so fertility falls even where average income changes little. A shift towards rural living tends to raise fertility rather than lower it.

A city imports food, water, fuel and construction materials and discharges sewage, solid waste, waste heat and flue gases. Its urban metabolism is best described as

• circular, because the outputs are returned as inputs to the same system
• closed, because the city boundary prevents matter from crossing it
• linear, because resources pass through the system and leave as waste
• isolated, because neither matter nor energy crosses the city boundary at all

Answer: linear, because resources pass through the system and leave as waste

A linear metabolism draws in raw materials at one end and discharges waste at the other; a circular metabolism would feed outputs such as composted organic waste and reclaimed water back in as inputs. No city is closed, because matter crosses its boundary continuously.