nature.net
April 2007
Pop Charts
By Robert Anderson
Nowadays, when I fly, my two children compete for the window seat. But I remember when I used to be glued to the airplane window on approach to Los Angeles. The grid of streets and the sinuous system of freeways spread out for hundreds of square miles before me was always a vivid reminder of the remarkable expansion of our species. Just before landing, I would also note the traffic grinding along the 405 freeway. Our reproductive success, it seems, exacerbates almost every problem we face, from regional conflicts to global warming and the loss of biodiversity.
On the Internet scores of organizations analyze the numbers, sound warnings, and offer ways to soften the impact of future population growth. NOVA's Web site World in the Balance is a good introduction to the subject. Beneath the heading, a “popclock”—a ubiquitous feature on population sites—counts each moment's increase in our numbers (as I write, it is speeding past 6,569,308,148). In the “Interactives” section, click on “Human Numbers Through Time” for a series of nine maps that show the spread of our species across the globe (to animate the maps, click through to the last one and then select “play all,” which appears just above the map on the right). For authoritative current statistics on many of the social factors that affect birthrates throughout the world, go to the Population Reference Bureau and click “Datafinder.”
Globally, in this century, the least developed regions will undergo nearly all the growth. For a quick look at where people live, go to the Hive Group, which specializes in visualizing business data. Here you can readily compare the populations of various countries.
The Social and Spatial Inequalities Research Group at the University of Sheffield in England has an addictive Web site called Worldmapper that shows how humanity and resources are distributed. The countries are sized to reflect the numbers, whether they describe population, health, literacy, or any of hundreds of other societal attributes. Under “Map Categories” select “Basic” for various population maps, including ones predicting the numbers for 2050 and 2300. The growth rate of global population has now slowed to about 1.15 percent per year, which may not seem high. But to get a sense of what that really means, go to Understanding Exponential Growth, by Greg Bothun of the University of Oregon. Near the top of the page you'll find a link to a simulator where you can explore how population will affect greenhouse-gas emissions. At the bottom click on “next lecture” to learn more about the math of population dynamics.
As clever as our species is, we are not immune to many of the same physical restraints that keep other animal populations in check. On the page Human Carrying Capacity of Earth, Gigi A. Richard, a geologist at Mesa State College in Grand Junction, Colorado, ponders how many people the planet can ultimately sustain. Her startling conclusion: fewer than are alive today. She cites biologist Dave Klein's classic study of the “carrying capacity” for reindeer on St. Matthew Island, Alaska. After the reindeer outstripped the island's food supply, their population simply crashed (see When Reindeer Paradise Turned to Purgatory). Such ecological disasters culled human populations in the past; perhaps the most ominous example was the demise of the people of Easter Island (click on “Out of House and Home,” also at the World in the Balance). Inevitably, part of the story of this century will be about how we come to grips with our “success.”
Robert Anderson is a freelance science writer living in Los Angeles.
Copyright © Natural History Magazine, Inc., 2007