Elderly to outnumber the young
The residents of those cities will also see a generational shift, he said, as the aging start to outpace the young. By 2065, Cohen expects aging to have "gone global," with people over the age of 65 outnumbering children under the age of 15.
"The slowing population growth will not solve all of humanity's problems," he said. "But it will make it much easier to solve many of them by slowing growing demands for more teachers, jobs, schools, appliances, energy, land, water and food."
Cohen's lecture was the prologue here to a roundtable of Columbia academics brought together to discuss "the 7 billion challenge." In a video on the subject, Earth Institute Director Jeffrey Sachs celebrated the upthrust in population as "a pivotal global moment" while calling it a threat to human existence as we know it.
Feeding 7 billion already requires so much fertilizer that fresh water around the globe is in danger, Sachs said. He also pointed to "huge dead zones" in estuaries of more than 100 rivers, the carbon costs of massive energy consumption and ongoing deforestation to feed the masses.
Sachs said he hopes the 7 billion moment will help bring attention to the "unprecedented, extremely dangerous and unsolved problems of human impact." On climate change, for instance, Sachs sees a planet "barreling forward" without much sense for "how objectively unsustainable we already are."
Fertility rate drops; consumption doesn't
"We have absolutely no evidence over the last 20 years that we've accomplished anything on climate change," he told the conference. "We're in a pretty serious state of affairs."
Others saw the moment in similarly mixed terms. Ruth DeFries, a professor of sustainable development at Columbia, said she chooses to view the population mark "as a success," because it is "the goal of any species to increase its numbers." But she also sees no end in sight for consumption increases.
Not even the lower fertility rate is expected to halt human consumption, because the output of a single human being continues to grow, she said.
"While we see a decline in fertility, we don't see a decline in the consumption of resources," she said. "We don't really have a clear pathway to deal with this."
Others were a touch less dire. Jean-Marie Guéhenno, director of Columbia's Center for International Conflict Resolution, said he would expect ongoing population growth to "trigger a lot of mobility" between nations, which could correspond to economic opportunity. Between Europe and Africa, for instance, Guéhenno senses "an enormous potential from a European standpoint."
"Here is next door a continent that can become a huge market," he said.
Klaus Lackner, a geophysics professor at Columbia, struck an equally evenhanded note. With population growth showing signs of slowing, Lackner said, it may actually come to a stop, at which point technology -- especially in energy -- might start to handle higher demand.
"Better wealth, better education ultimately solves the problem," he said. "We just might solve the resource question, in time."
Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500