Controlling population really isn't the magic bullet people see it to be. People look for a quick fix, and more importantly one that doesn't require them to change their lifestyle. In many respects human population control measures fit this bill. People making these suggestions tend to be educated, fairly well off (as in having some amount of disposable income and making a good living when compared to the majority of the world), and live in developed nations. Statistically speaking people with these criteria tend to have fewer kids compared to people with less education or living in developing nations. Because of this they see population control measures effecting other people, not them. Population growth is a southern hemisphere problem, a developing nation problem, a less educated section of society's problem, etc and "those" people need to be controlled, because they are having a large number of kids and causing the population to grow at a fast rate. Once control measures are adopted suddenly resource consumption drops, environmental pressures ease, and life is good. Or so we thought.
A lot of recent work (last 5 years) has discovered a much different reality. A paper by Liu et al. (2003) showed that household dynamics- basically how many people live in a household, affluence of the household, resource consumption etc- really this plays an even more important role than straight up population size does. Even more interesting in areas identified as biological hot spot by Conservation International (regardless of their location in developed or developing nations) the number of households is growing at a much faster rate than population.
So even though the number of people is staying the same or growing at a certain rate (average growth rate in hotspot countries was 1.8%) the number of households is increasing at a much faster rate (those same countries average of 3.1%). While this is happening the number of people living in a household is decreasing substantially so households are becoming less efficient. Even if we had zero population growth (or even a decrease in population growth which is occurring in some countries) as of today, consumption (and environmental impact) would continue to accelerate.
Think about it this way. You have 5 people in a population and they all live in the same house- that is going to use substantially less resources than 4 people living in 2 houses because that 5 person house is 1) going to use the same amount of energy to build, heat, and maintain regardless of the number of people in it, 2) the same amount of infrastructure (roads, gas lines etc) goes in regardless of how many people live in it. Conversely even though there is one fewer person in the 4 people 2 house scenario they over all will use more resources than 5 people living in a single house. Yes 5 people in 1 house will eat more food and use more water, but the overall impact will still be less than 4 people in 2 houses because of the efficiency differences. For instance, two-person households in the
Population control measures themselves can also result in higher environmental impacts. For example affluence- if you have 3 kids and make somewhere around the poverty level you are basically just scraping by, have a pretty small house, and not a lot of money to spend on things like cars or other "luxury items". But if you make the same amount of money and only have one kid you are going to have a lot more disposable income. This translates into larger houses (average house size in
So while there may be fewer people those fewer people are having a much larger effect on the environment. This doesn't even address the fact that people living in cities have a much lower environmental impact that those that live in rural situations, which I’ll hit on briefly at the end.
What can be done
Resource consumption is what really needs to be targeted, but who wants to be told that they can live in a smaller house just fine (seriously why do 2 people need a 1,500square foot house), to walk instead of drive their car to the grocery story, etc. This is the answer that educated people in developed countries do not want to hear because it will involve changes in their behavior.
Interestingly enough being oriented towards the environment such as a feeling of environmental activism, participation in recycling programs, or donating to environmental causes seems to encourage people to live in more sensitive areas and more resources (Peterson et al. 2008). Think about it, people who like nature want to live in nature- house in the country, etc. A house in the country is much worse ecologically than living in an apartment in the city, or even a house in the city because infrastructure had to be created in order to live there. So ironically people who tend not to consider themselves “environmentally oriented” in general have a smaller environmental impact. Additionally, people living in natural areas tended to have much smaller households compared to people living in previously developed areas.
So rather than advocating for population control measures environmentalists should be pushing for household control measures- making people live in smaller houses, having more people per household, and encouraging people to live in urban areas rather than moving to rural regions.
Below are a few papers people should check out. Keilman 2003 and Liu et al. 2003 explain household dynamics. The Liu paper especially set off a wave of research. Liu and Diamond 2005 examines
Keilman, N. 2003. The threat of small households. Nature. 421: 489-490
Liu, J., G. C. Daily, P. R. Ehrlich, and G. W. Luck. 2003. Effects of household dynamics on resource consumption and biodiversity. Nature 421:530–533.
Liu, J. and Diamond, J. 2005.
Peterson, M. N., M. J. Peterson, T. R. Peterson, and J. Liu. 2007. A household perspective for biodiversity conservation. Journal of Wildlife Management 71:1243–1248
Peterson, M. N., X. D. Chen, and J. Liu. 2008. Household location choices: Implications for biodiversity conservation. Conservation Biology 22:912–921