Today is the first day in history when 7 billion humans are alive all at once, according to U.N. estimates. The organization has symbolically declared Danica May Camacho, a Filipina baby born at 11:58 p.m. Sunday, as the 7 billionth person on Earth.

This is just the latest milestone in humanity's long-running population grand prix, but it may still mark a turning point. We've doubled our global population in the past 44 years — a feat that took us 57, 110 and 500 years the previous three times — and another 2 billion babies are expected in the next three decades. But our global growth rate is also slowing down, having dipped to 1.1 percent after peaking at 2.2 percent in 1963. It's forecast to be 0.5 percent by 2050.

And even though we're hitting the ominous 7 billion mark on Halloween, the U.N. insists we shouldn't be scared — just better prepared. In its new State of the World Population report, the U.N. Population Fund echoes a growing sentiment that 7 billion in 2011, or even 10 billion in 2100, can be sustainable under the right conditions.

The average human life expectancy has already risen from 48 to 68 years since the 1950s, and many experts argue that if we keep improving our quality of life — especially via education and health care for women — the quantity will take care of itself. That's based on the idea that total fertility rate, or the average number of children born per mother, tends to drop as education, health and wealth increase. There are exceptions, but the graph below shows a strong correlation, using CIA data for each country's total fertility rate and per capita gross domestic product (GDP):

Image: Wikimedia Commons / Data: U.S. Central Intelligence Agency (1, 2)

[skipwords]The key to curbing population growth in developing countries, many experts say, is to help them become developed countries. That's a big task, but even subtle upgrades in education and health care can be significant. As Columbia University population researcher Joel E. Cohen tells Reuters, "in many developing countries, women who complete secondary school average at least one child fewer per lifetime than women who complete primary school only." And one mother's education can pay dividends for decades, adds Dr. Babatunde Osotimehin of the U.N. Population Fund, since "her children survive better, physically they mature, emotionally they mature, and because they have education, they are able to make choices."

Education isn't the only piece of the puzzle, though — the U.N. estimates that 215 million women want to delay or prevent pregnancies but lack modern birth control, while the Worldwatch Institute estimates "more than two in five pregnancies worldwide are unintended" by the mothers. According to the Guttmacher Institute, more than half of all reproductive-age women in the developing world live in just three regions (Sub-Saharan Africa, South Central Asia and Southeast Asia), where an estimated 70 percent of them have unmet needs for contraception.

"If all women had the capacity to decide for themselves when to become pregnant, average global childbearing would immediately fall below the 'replacement fertility' value of slightly more than two children per woman," the Worldwatch Institute reports. "Population would then move onto a path leading to a peak followed by a gradual decline, possibly well before 2050."

Sustainability still isn't quite that simple, though. We're already locked into a growth pattern that will likely yield 10 billion people by 2100, so Worldwatch adds that we must also learn to use limited resources like food and freshwater more efficiently. "Humans appropriate anywhere from 24 percent to nearly 40 percent of the photosynthetic output of the planet for food and other purposes," the group says, "and more than half of the planet's accessible renewable freshwater runoff."

According to the U.N. Food and Agriculture Organization, about one-third of all food prepared for humans (1.3 billion metric tons) is wasted yearly. And as the World Resources Institute points out, such careless consumption habits are at least as newsworthy as our raw numbers. "Far more damaging than the booming birth rate in low-income countries," the WRI's Manish Bapna recently wrote, "are the resource-intensive lifestyles of the global rich and middle class." Thanks largely to these lifestyles, 60 percent of the planet's "ecosystem services" are deteriorating due to overuse, the WRI concluded in a 2005 report. Our rate of water consumption, for example, is now outpacing our rate of population growth.

Overpopulation remains a serious problem across much of the world, even as some wealthy countries face the reverse issue of population decline. The specter of climate change, which may spur droughts and storms that cause famine, only adds to the seriousness. But modern technology, along with an increasingly mainstream focus on sustainability, offers a reason to be optimistic, the U.N. and other research groups suggest. In its 2011 State of the World Population report — subtitled "People and Possibilities" — the U.N. presents this overview on the significance of 7 billion:

"Our record population size can be viewed in many ways as a success for humanity: People are living longer, healthier lives. But not everyone has benefited from this achievement or the higher quality of life that this implies. Great disparities exist between and within countries. Disparities in rights and opportunities also exist between men and women, girls and boys. Charting a path now to development that promotes equality, rather than exacerbates or reinforces inequalities, is more important than ever."

In honor of today's 7 billionth person, check out the timely tune below called "7 Billion People All Alive At Once," by instrumental rock band And So I Watch You From Afar. It's from the album "Gangs," set for a Nov. 8 release in North America, and guitarist Rory Friers explains in an email to MNN that "it's a song about people, and 7 billion covers pretty much everyone."[/skipwords]

Also on MNN:

The opinions expressed by MNN Bloggers and those providing comments are theirs alone, and do not reflect the opinions of While we have reviewed their content to make sure it complies with our Terms and Conditions, MNN is not responsible for the accuracy of any of their information.