Life as a falconer, insect systematist, and double Masters Student (or a look into the mind of someone who is questionably sane).

24 April 2009

Why human population control isn't the answer to the world's problems

Its weird how things in my 2 worlds (falconry and Ecology/Evolutionary Biology) seem to mirror each other. The last two weeks of one of my ecology classes have been dedicated to human pop dy issues, and I woke up yesterday morning to find a thread on IFF advocating human population control. Well after a pretty extensive literature review on why this really won't work I spent a large chunk of my day typing up responses rather than putting the finishing touches on my thesis. It's a week before my defense anyway, so no rush. After all this time I figured may as well write a blog post on the subject so here it goes.

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 United States in 1993–94 used 17% less energy per person than one-person households (O’Neill, B. and Chen, B. 2002). When you have a great increase in the straight up number of households this is a huge deal because now you've got more strain on the environment for the same number of people.

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 China for example has tripled since 1980 while household size in that time has decreased), more cars (again in China from about 2 million to over 20 million), and other status symbols (China data from Liu and Diamond 2005).

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 China’s impact on the environment and looks at trends over the last 30 years. Peterson et al. 2007 is a more theoretical paper discussing why household control measures should be preferred over population control. Peterson et al. 2008 looks at various facts about a household and how they impact location (and environmental impact).

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. China's environment in a globalizing world. Nature. 435: 1179-1186

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

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