World population stabilization unlikely this centuryPatrick Gerland et al. Science, forthcoming Abstract: The United Nations recently released population projections based on data until 2012 and a Bayesian probabilistic methodology. Analysis of these data reveals that, contrary to previous literature, world population is unlikely to stop growing this century. There is an 80% probability that world population, now 7.2 billion, will increase to between 9.6 and 12.3 billion in 2100. This uncertainty is much smaller than the range from the traditional UN high and low variants. Much of the increase is expected to happen in Africa, in part due to higher fertility and a recent slowdown in the pace of fertility decline. Also, the ratio of working age people to older people is likely to decline substantially in all countries, even those that currently have young populations.From Science Daily:
Most of the anticipated growth is in Africa, where population is projected to quadruple from around 1 billion today to 4 billion by the end of the century. The main reason is that birth rates in sub-Saharan Africa have not been going down as fast as had been expected. There is an 80 percent chance that the population in Africa at the end of the century will be between 3.5 billion and 5.1 billion people.Other regions of the world are projected to see less change. Asia, now 4.4 billion, is projected to peak at around 5 billion people in 2050 and then begin to decline. Populations in North America, Europe, and Latin America and the Caribbean are projected to stay below 1 billion each.Above I’ve used Google to plot Total Fertility Rates (projected babies per woman per lifetime) for the three most populous countries in Africa. The TFR in Ethiopia has been falling, but is still well above 4. In Nigeria and Congo, its at six.The concept of Demographic Momentum needs to be understood. Say that tomorrow, the TFR in Nigeria and Congo instantly dropped from 6 to the replacement level of 2. Would the population stabilize immediately? Not for many decades. You see, the women who are having six children today would still wind up having 12 grandchildren, whereas in a country where the TFR has been stable at 2 for a generation, mothers can expect to have four grandchildren eventually.But in both Nigeria and Congo, there really hasn’t been a trend toward substantially lower TFRs over even the last half century.Environmental reporter Andrew Revkin writes in the New York Times:
Yeah, logic is racist.
The United Nations and the streets of Manhattan are going into global warming saturation mode, from Sunday’s People’s Climate March through the Tuesday climate change summit convened by Secretary General Ban Ki-moon and on through an annual green-energy event called Climate Week.
Largely missed in much of this, as always seems the case with climate change discussions, is the role of population growth in contributing both to rising emissions of greenhouse gases and rising vulnerability to climate hazards in poor places with high fertility rates (think sub-Saharan Africa).
That’s too bad given that on Monday a separate special session of the General Assembly is scheduled to hold a 20th-anniversary review of actions since the International Conference on Population and Development in Cairo. As Bob Engelman of the Worldwatch Institute mused at a Wilson Center meeting in Washington last week, there needs to be much more crosstalk.
Obviously, rates of consumption of fossil energy and forests per person matter more than the rise in human numbers. As I’ve said before, 9 billion vegan monks would have a far different greenhouse-gas imprint than a similar number of people living high on the hog.
But family planning, for instance, should absolutely be seen as a climate resilience strategy in poor regions. This is how I put it in 2010:
Africa’s population is projected to double — from one to two billion — by 2050. That means exposure to [deep, implicit] climate hazards will greatly increase in many places even if climate patterns don’t change at all. So family planning, and sanitation and water management, sure sound like vital parts of any push for climate progress.
I’d be happy to shift my view if someone can explain a flaw in my logic.