Geoffrey McNicoll

Australian National University and

Major demographic fluctuations over large populations are historically rare. Changes that are locally drastic disappear in global aggregates. Even the greatest demographic catastrophe in modern history - the 1959-61 famine in China associated with the Great Leap Forward policy, which resulted in 30 million excess deaths and a 35 million deficit in births - had a barely perceptible impact on the curve of world population growth. Simulations of India's population trajectory show that introducing sharp mortality peaks at regular intervals has only a slight effect on the course of India's population growth. Thus it makes sense for demographers to work generally with "surprise-free" projections - making assumptions of smooth trends in mortality and fertility.

Over the long run, small differences in fertility are enormously consequential. The United Nations (UN) long term population projections demonstrate this sensitivity.

As Figure 9.1 shows, a fertility rate that stabilizes at 2.06 children per woman ("replacement level") results in a world population of 11 billion in the year 2150 (UN medium projection); at the slightly higher level of 2.17 children per woman, the 2150 population reaches 21 billion (UN medium-high), and at the slightly lower level of 1.96 children per woman, the population reaches a peak of 8 billion in 2050, then falls back to 6 billion in 2150 (UN medium-low projection).

Commenting on the efforts to model population-environment interactions, McNicoll noted the estimate by Bongaarts that population growth accounts for one-third of the projected rise in CO2 emissions by 2100. However, since this calculation already assumes a falling rate of population growth (in line with the UN medium projection), it does not offer a new demographic route to lower emissions. McNicoll was skeptical of the feedbacks on mortality from population-caused pollution and soil degradation introduced in the models of Meadows and colleagues (Limits to Growth, 1972, Beyond the Limits, 1992). However, he did not rule out possibilities for demographic collapse in the future - not necessarily associated with feedbacks from population growth.

He offered a six-part categorization of "demographic surprise" scenarios that might lead to regional or global population collapse:

1. atmospheric dust/aerosols impede photosynthesis and cool Earth's surface, triggering crop failure and perhaps killing other vegetation; ex.: major volcanic eruptions; "nuclear winter"
2. disease: new or newly virulent pathogens affect humans or crops; ex. in the past: smallpox, measles; in the future: new viruses, perhaps some more infectious variant of HIV.
3. climate change, exceeding adaptive capacity of agricultural systems or supporting ecosystems; ex.: shift in ocean currents affecting coastal temperatures, new pest regimes, forest die-off.
4. environmental degradation from human impact, yielding population overshoot and collapse; local examples are common but global analog seems implausible (except through climate change).
5. breakdown of physical infrastructure, such as distribution systems supplying major cities, irrigation systems, etc., typically resulting from war.
6. institutional breakdown: erosion of legitimacy or performance of institutions of state and economy; ex.: "failed states" such as Liberia, Sierra Leone, Somalia.

McNicoll viewed the first three as potentially global phenomena, the last three as more likely to be regionally confined.

What scope is there for deliberate modification of the demographic future through policy intervention? McNicoll argued that the policies that have proven effective are:

1. rapid economic growth, leading to "demographic transition" along the lines that occurred in the industrialized world; affluence and equity lead to lower fertility.
2. authoritarian control by a government able to enforce compliance with its demographic goals and not much concerned with human costs; China in 1970s is the principal example.
3. "fortuitous institutional inheritance" - situations where social or cultural pressures to curtail fertility emerge naturally as population increases, with minimal need for a government role; there is scope for policies that seek to create those situations through institutional reform (e.g., in land tenure, local finance, women's emancipation).

McNicoll was skeptical that distribution of contraceptives through family planning programs had a strong independent effect on fertility. (He judged the empirical evidence on the matter to be inconclusive.) He noted that current emphases in international population policy were on education and women's empowerment, which would tend to reduce fertility by affecting the demand for children. The debates leading up to the 1994 International Conference on Population and Development in Cairo stressed this direction.

During the discussion, some took exception to the notion that distributing contraceptives was ineffective, noting that if the 120 million couples who want but do not have access to contraceptives were given them, we could cut population in the year 2050 by 2 billion.