What’s “crowded”?
Posted by Dave on March 10, 2010 | No Comments
Here in Mecklenburg County, North Carolina, I get annoyed when the four-lane expressway into Charlotte gets clogged up. Sometimes it takes 40 minutes to drive the 23 miles into town. Sometimes I’m even bothered when I drive to the neighboring town of Cornelius (population, 15,000), and I have to wait two light-cycles to make a left turn.
So there are times, living in my small suburban town, when it feels a bit crowded. Mecklenburg County’s population density, at about 700 residents per square kilometer, is actually fairly high compared to most of the world. This Wikipedia page calculates that if population were spread equally around the world, average density would be just 44 per square kilometer (of course, that would put a lot of people in places like Antarctica and the Sahara Desert). Manhattan’s density is over 25,000 per km2—over 30 times the density here.
But take a look at this map of world population density:
You can click to see a larger image on Wikipedia. Even the densely populated US east coast still pales in comparison to most of Europe, China, and India. But even this map doesn’t tell the whole story. Places like Charlotte—the most populated urban area in my state—don’t even make the top 200 most populated cities (PDF link). And my county’s density is as high as the scale goes on the map!
Sure, I can drive 20 miles and be among skyscrapers. But if I drive 20 miles in the opposite direction, I can be out of sight of any other human.
I suspect if you ask most people if the world is too crowded, they’ll say yes. But “crowding” isn’t really the problem. People move to urban areas because that’s where jobs are in modern economies. There are still plenty of places that have very few people. The green and orange regions of the map are habitable areas with fewer than 40 people per square kilometer—less than a tenth the density of Mecklenburg County.
Only the pinkish-purple areas on the map are as dense as Mecklenburg—and as you can see, they don’t take up much space at all. Most of the world really isn’t crowded. In my dense county, I’ve got a big house, with trees and birds in the back yard. I even spot an occasional deer within a block or two of my house.
That’s not to say that “population” isn’t a problem. As we’ve seen, the large number of people—especially affluent people—in the world are directly responsible for some of the most significant problems we face today. But that’s the subject of another post.
Population optimism: A global eco-techno-utopia
Posted by Dave on March 9, 2010 | 1 Comment
Last summer, my wife Greta and I spent a glorious week with old friends in a lovely home on the Maine coast, immersed in wilderness and beautiful isolation:
That’s Greta and our friend Suzanne waving from the deck. Isn’t it just wonderful?
Yet a home like that is completely out of reach for the vast majority of the world’s population, isn’t it? Even if everyone could afford such a place, there simply isn’t enough land on the planet to house everyone in such luxury, right?
Maybe not. Sure, some of the scenarios I discussed last week suggest that global population is limited primarily by scarce resources. In order for global population to stabilize, people must reach a limit of the amount of resources available. Population decline isn’t pretty—it’s accompanied by illness, hunger, and deprivation.
But Friday’s post, while depressing in some ways, also offers a way out. While population is growing rapidly in some parts of the world, it’s slowing in others. Where is population growth slowing down? In the wealthiest nations—with the exception of the US, where population increases are sustained primarily due to immigration.
In an essay in Prospect in 2004, Michael Lind argued that a different world future, one with a stable global population that sustains our natural resources, is quite attainable. There are a couple caveats. First, Lind accepts the widely-touted figure of 9 billion as the level where world population will settle. Second, he assumes (hopes?) that the developed nations of the world will take a leadership role in protecting the environment and developing technology that will bring modern conveniences to everyone on the planet.
Booming world population doesn’t mean growth everywhere
Posted by Dave on March 5, 2010 | 4 Comments
Population changes don’t affect all nations equally at once. While population in some countries is increasing rapidly, in others it’s slowing or even declining. Take a look at the case of Japan and Nigeria:
|
Nigeria
|
Japan
|
|||
|
1950
|
2005
|
1950
|
2005
|
|
| Population (Millions) |
32.8
|
131.5
|
83.6
|
127.7
|
| Lifetime births per woman |
6.9
|
5.9
|
2.8
|
1.3
|
| Annual births (Millions) |
1.7
|
5.6
|
2.1
|
1.1
|
| Annual deaths (Millions) |
1.0
|
2.5
|
0.8
|
1.0
|
| Population under age 15 (percent) |
42
|
44
|
35
|
14
|
Currently Nigeria and Japan have nearly equal populations, but in 1950, Japan’s population was almost three times larger than Nigeria’s. Nigeria’s birthrate has barely budged, while Japan’s halved over that period. Life expectancy has increased in both countries, but in Japan this increase has been overwhelmed by its plummeting birthrate. Now annual births barely exceed deaths, and its population is expected to start decreasing in the very near future. Japan’s average income per person was thirty times larger than Nigeria’s in 2004, where 91 percent of the population lived on less than $2 per day. That would barely cover my daily cookie allowance, let alone provide my entire means of sustenance.
This data all comes from a 2005 paper by Mary Kent and Carl Haub. They make a fairly convincing case that considering “global population” without thinking about regional differences is pretty much pointless.
While population is growing rapidly in Africa, South Asia, and Latin America, it’s stabilizing in much of East Asia and beginning to decline in Europe. Even if we agree that increasing global population is a problem (and we may very well not agree), increasing population is the least of worries in many places.
What does it mean to be “overpopulated”?
Posted by Dave on March 3, 2010 | 5 Comments
Population increases when the birthrate exceeds the death rate, and decreases when the reverse occurs. So what does the world look like when there are too many people?
One way to approach this question is to consider what the limiting factors in population are. When, exactly, does the death rate exceed the birthrate? A key consideration is mortality. If people live shorter lives, the death rate goes up, and population goes down (or at least grows more slowly). What causes mortality to increase? Obviously things like wars, pandemics, and famines have an impact, but economist Robert Fogel argues that these are actually a relatively small part of the global mortality picture.
Fogel, who won the Nobel prize for economics in 1993, runs the Center for Population Economics at the University of Chicago. In 1994 he wrote an influential working paper that arrived at a startling conclusion: By far the biggest historical contributor to mortality is the amount of energy consumed in food compared to nutritional requirements. Eat less, die sooner. In order to survive, a man in his 20s or 30s requires between 1,700 and 2,500 kcal of energy per day, depending on height. This provides exactly enough energy to eat and take care of basic hygiene. Any work — even just strolling for an hour or two — requires additional food.
In England in 1790, the total amount of food consumed was about 2,300 kcal per person per day. For men in their 20s and 30s about 2,700 kcal/day was consumed—on average—which means that many people were consuming barely enough to make it through the day. Indeed, by Fogel’s estimates, three percent of the labor force didn’t consume enough energy to do any work at all. In France, that figure was more like ten percent. The bottom 20 percent of the English work force had only enough energy for about 1 hour of heavy work or 6 hours of light work per day. No wonder English literature from that period is rife with descriptions of impoverished beggars. There simply wasn’t enough food in England to support them in any other line of work.
But total food consumed isn’t the only factor in determining whether a person will live. The key is to compare consumption to requirements. Smaller people need less food. In England in 1800, the average man weighed substantially less than today—about 140 pounds (56 kg). In 1700, the average was even lower: 118 pounds (46 kg). If men in 1700 had been as big as they were in 1800, they wouldn’t have had enough excess energy to do any work outside of agriculture.
How can we predict world population growth?
Posted by Dave on March 2, 2010 | 3 Comments
Predicting the future is always difficult. Who could have known in the year 1775 that 100 years from then, ships and trains powered by coal would allow people to circle the earth in weeks rather than years? Who could have predicted that in another 100 years, the human voice—and moving images—would be able travel that distance in less than a second? Now we have much more sophisticated tools for prediction, but prognostication remains elusive.
But never has predicting the future had stakes as high as it does now. Precisely because of the technological advances that have transformed the world in the past two centuries, we need prediction to ensure our technology doesn’t kill us. We already had one near miss, with the near destruction of the ozone layer due to chlorofluorocarbons and other pollutants. In his book The Weather Makers, Tim Flannery estimates that 50 percent of the UV protection provided by the ozone layer for people living in middle latitudes would have been lost by 2050 if we hadn’t taken steps to stop it. Instead, the ozone layer will likely be fully restored by that date.
But population involves so many other variables that predicting it more than a decade or so into the future is quite difficult, and models for future population changes vary widely. Today I’m going to consider just one model for population growth and its impact on the economy and carbon emissions.
A team led by Salvador Puliafito took a look at global population data from 1850 to the present and then tried to develop a model that would predict population through 2150. They based their model on a set of equations originally developed for tracking predator-prey relationships in ecological systems. You may have seen it in your high school biology textbook; it’s called the Lotka-Volterra model and it looks like this (source: Wikipedia):
The idea is simple. Imagine an island like Isle Royale in Lake Superior, where wolves feed primarily on moose. If there are lots of moose in a given year, there’s plenty of food for the wolves, and the wolf population will grow. But eventually the wolves will kill off the moose, and the moose population declines. Naturally, with less food, the wolves die off too. With fewer predators, the moose population recovers, and the cycle starts over again.
Are there too many people in the world?
Posted by Dave on March 1, 2010 | 9 Comments
We’re in a carbon emergency, we’re told. The world is producing too much carbon, and more every year, resulting in possibly irreversible global warming. But take a look at this graph (via Google):
If we’re in an emergency, why hasn’t carbon output gone up appreciably since 1970? The answer, of course, is that this graph measures per capita carbon output. While the average output per individual hasn’t risen in the last 40 years, the population has increased drastically:
Closing a chapter on HIV and AIDS
Posted by Dave on February 26, 2010 | 3 Comments
I end this first month of The Daily Monthly feeling tremendously fortunate. Not just because I’m healthy when so many others are not, but also because I’ve connected with some amazing individuals.
I’m glad to know that there are dedicated people trying to find a cure for HIV and AIDS, and others committed to helping those who are already HIV positive. I’m glad to see that many people, despite being sick themselves, are devoting their lives to helping others, either through HIV and AIDS prevention efforts, or by offering comfort and companionship to others who have AIDS. Although it’s time for me to move on, I know they’re going to keep on doing what they are doing, and that gives me hope for the future.
There have been days on this project when I wasn’t sure I would make it to the end of this month, juggling my other responsibilities with starting a new blog. It would be trite to say that I was inspired by the battles others are waging with HIV, and that’s what pushed me to finish.
It would also be untrue.
While I do think the people I’ve met this month are amazing, they’re not what motivated me to finish this month of reporting on AIDS in America. That motivation could only come from my own desire to make this site work.
AIDS, stigma, and finding a cure
Posted by Dave on February 25, 2010 | 2 Comments
One of the first things Amy Brooks told me when I interviewed her about this project is that she was concerned that AIDS was becoming “just another chronic disease.” Part of the reason HIV and AIDS tend to be forgotten in the public health landscape is that they are, to an extent, manageable, just like heart disease, diabetes, and breast cancer. Though clearly thousands of people here in America are struggling with AIDS, I’ve met people who have done all right living with AIDS for more than 20 years.
I’ve thought about that a lot over the course of the past month. What would my month have been like if, instead of AIDS patients and doctors, I visited cancer patients and doctors? While clearly many families face horrific battles with cancer, can we say HIV and cancer are comparable? Well, it would have been different because the diseases are different. Cancer isn’t actually a monolithic “disease” — it comes in many forms. Skin cancer, while it can be deadly or disfiguring, is usually treatable. Breast cancer, which has a comparable death rate to AIDS, is treated over a period of a couple years, while treatment for AIDS continues for life. Pancreatic cancer, unlike AIDS today, is nearly always deadly.
There are thousands of heart-wrenching stories about families dealing with cancer, just as there are with AIDS. But even if the symptoms and treatment of HIV and some other disease were similar, HIV has its own unique set of issues. It disproportionately affects people of color: African Americans are about 7 times more likely to contract HIV than Caucasians. It is acquired through activities that many people find immoral: by far the most common means of transmission in the US are men having sex with men, and intravenous drug use. There are many people opposed to AIDS education simply because they don’t want their children learning about the types of activities that cause it.
How close are we to a cure for HIV / AIDS?
Posted by Dave on February 23, 2010 | 4 Comments
When I began work on this month’s project, I contacted a clinician, a case manager, and a scientist to get their perspectives on how we’re making progress fighting HIV and AIDS. I’ve introduced you to the clinician and the case manager, but not the scientist.
Dave Wessner doesn’t actually study AIDS, but he’s written a textbook supplement on HIV and AIDS and teaches a course at Davidson College on the subject. His students have even set up a blog discussing the history and science of HIV and AIDS. He also regularly lectures on the topic. I’ll be attending one of his talks tonight.
I asked Dave to point me to good research about the HIV virus and he showed me a 2003 review written by Stephen Goff and published in Cell. It’s a fascinating article, showing how a “seemingly minor” protein encoded in the HIV genome is actually responsible for a critical defense the virus uses against the human immune system.
As I mentioned last week, the HIV virus hijacks the apparatus of one type of cell in our immune system in order to reproduce. It’s a multi-step process, and anti-HIV drugs typically work by disrupting one or more steps in the process. Goff’s article explains how the tiny protein Vif actually stops the immune system itself from disarming the HIV virus. Humans have a protein called APOBEC3G that normally attaches itself to the virus as it’s budding off the human producer cell:
A quick poll: Do you want to know how an individual got HIV?
Posted by Dave on February 19, 2010 | 8 Comments
I’m extremely busy today with judging the Research Blogging Awards so I won’t be able to offer a substantive post, but over the course of this month I’ve become quite curious about one thing. When you learn about someone with HIV or AIDS, do you want to know how they got it? Let’s make this a poll:
I’ve never asked anyone I interviewed how they became infected with HIV. Three people have volunteered the information, but I decided not to share it here. I have a little more to say on this, but I’m placing it below the fold so you have a chance to answer before you see my views on the subject.
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The Daily Monthly is Dave Munger's multi-layered exploration of ideas and issues affecting all of us today.
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