A new study in PNAS by O’Neill et al. (2010) describe “population shifts” as having a substantial influence upon greenhouse gas emissions. From the abstract of Global demographic trends and future carbon emission:
Substantial changes in population size, age structure, and urbanization are expected in many parts of the world this century. Although such changes can affect energy use and greenhouse gas emissions, emissions scenario analyses have either left them out or treated them in a fragmentary or overly simplified manner.We carry out a comprehensive assessment of the implications of demographic change for global emissions of carbon dioxide. Using an energy–economic growth model that accounts for a range of demographic dynamics, we show that slowing population growth could provide 16–29% of the emissions reductions suggested to be necessary by 2050 to avoid dangerous climate change. We also find that aging
and urbanization can substantially influence emissions in particular world regions.
Thankfully, the authors did not make any assumptions about how reduced population growth would occur. From the discussion: (O’Neill et al. 2010)
Economic development is one factor that can facilitate declines in fertility and slower population growth. If it were assumed that increases in economic growth rates were driving fertility decline, our results would differ: faster economic growth would have an upward effect on emissions, offsetting the emissions reductions caused by slower population growth to some degree.
And from the final paragraph:
However, more rapid economic development is not the only factor, or a necessary one, in facilitating fertility decline. Policies can also significantly affect fertility trends. Although the appropriateness of policies that encourage even lower fertility in countries where it is already low is debatable and would require consideration of the trade offs associated with increased aging (29), in other regions, there are several such policies already considered desirable in their own right. For example, household surveys indicate that there is a substantial unmet need for family planning and reproductive health services in many countries. Policies that meet this need would reduce current fertility by about 0.2 births per woman in the United States (30) and 0.6–0.7 births per woman in the developing world (SI Text has details of this calculation). This reduction is comparable with the 0.5 births per woman difference in fertility assumptions between the population scenarios used here. In our analysis, emissions reductions in these regions (i.e., the United States and developing country regions other than China) amount to about one-half of the total reductions that result from following a lower global population growth path, suggesting that family planning policies would have a substantial environmental cobenefit.
Note the paper is freely available online through the PNAS open access option. Nature.com has a blog posting that’s helpful:
Aging reduces emissions as elderly people contribute less to economic growth. Urbanization has the opposite effect: The migration of people from the countryside to large cities boosts the supply of labour and so fuels economic growth and the demand for energy, the study finds.
Aging is likely to dominate future demographic development in most industrialised countries, the study concludes. But in China and India, which together account for more than one third of global population, urbanization is likely to be the key factor.
Ben D:
At October 13, 2010 at 5:23 pm you say of GM:
“his take on what Liebig’s law means is what it means”.
Yes, and I stated “his take” on that before s/he mentioned Liebig’s law when at October 13, 2010 at 5:21 am I wrote:
“Your assertion that “all the concentrated resources will have been dissipated” displays a mistaken view of human existence. The clear mistake is that you are considering humans on the Earth to be like microbes in a Petri dish: the microbes die when they consume their resources.”
It can be seen that GM has not disputed that this is his view of human existence.
And, in that same post, I explained why considering humans that way is a mistake. GM has not answered the explanation in any way (except to insult anybody and everybody who rejected his silly assertions).
This matter is not trivial because the view espoused by GM is widely promoted by ‘greens’, and it is the cause of their hatred of human beings which induces them to call for culling of the human population.
As others have stated above, the ‘greens’ attempt to justify their calls for a cull by false arguments about “sustainability”. And, as others have also pointed out above, the test of whether something is sustainable is whether it is being sustained. The human population is more than sustainable because it is expanding.
The ‘greens’ ignore the foreseeable problems of population decline in the latter half of this century because they are so keen to cull people (other than themselves) now. Of course, that future decline will be a problem for future generations to solve with the methods they choose: only hubris would induce us to try to resolve it.
Also, we do have real problems (e.g. HIV and malaria in Africa, terrorist threats around the globe, etc.), and we are distracted from dealing with them if we waste time and effort on implausible, hypothetical threats such as population growth, ‘sustainability’, Peak Oil, etc..
Richard