This has created the impression that population is no longer a problem.
But that's not entirely true. While birthrates may be down, the overall population has still grown, because life expectancy has increased. Most of us don't die when we give birth. We go on living, breathing, eating, drinking, shitting, idling in traffic, jetting between cities, and consuming more and more of the dwindling resources we have with a child or two at our side.
And the equation is simple, right? The more people, the bigger the problem.
"Well, it's not a direct multiplier," McKibben said. He offers as an example an Amish family of eight "living simply" and having less of an impact than the average American Brady Bunch. "In global terms it's so much more about consumption."
Ehrlich and McKibben agree that's really the problem. "An important point, which is usually missed, is the next 2.5 billion people are going to have a much bigger impact than the last 2.5 billion," Ehrlich said.
According to his research, we've surpassed the earth's carrying capacity, and Americans are only able to overconsume because Africans, Indians, Asians and other developing countries are underconsuming.
If the entire world population ate and drank and drove around like Americans which is the aspiration of many we'd need two more Earths.
"The current population is being maintained only through the exhaustion and dispersion of a one-time inheritance of natural capital," the Ehrlichs and Gretchen Daily wrote in the 1997 book The Stork and the Plow (Yale University Press), in which they grapple with the question of a sustainable population for Earth.
Their answer: about two billion. How many are we now? Worldwide, 6.5 billion, which will rise to about 9 billion by 2050 with most of the growth slated for developing countries. Family planning and education are largely considered the primary factors in keeping the US population under control, and that's where international efforts have focused, according to Kristina Johnson, population expert for the Sierra Club.
This has required an artful dance around the Mexico City Policy, in place in one form or another since 1984, when Ronald Reagan refused aid to any international agencies that use any monies for abortions. So while we've managed to handle our head count at home, we've done the opposite abroad.
As for how to deal with our enormous abuse of natural resources, technology has long been hailed as the solution. The guiding principle has been that our children will be smarter than we are, so we'll leave it up to them to figure it out. However, as the Ehrlichs conclude in their most recent book, One with Ninevah (Island Press, 2004), "The claim that 'technology will fix the problems' has been around for decades decades in which the putative advantages of claimed technological 'fixes' have often failed to appear or proved to be offset by unforeseen nasty side effects."
For example, we essentially avoided large-scale famine by figuring out how to reap more crops from our soil. But we haven't mastered how to do this without the use of pesticides and, increasingly, genetically modified organisms that have transformed diverse farms into precarious monocultures.
Today we're counting on technology even more, but some of the proposed solutions still raise questions. Do we have enough acreage to grow biofuels? What would be the long-term impacts of capturing carbon emissions and burying them underground? Ditto for spent nuclear fuel.
And all of these variables factor in those 2.5 billion people to come, without suggesting people consider not having children.
If there's a mantra for any concerned citizen to adopt, it should be less. Use less. Buy less. Be less of a draw on the system.