According to recent projections, the number of people living on Earth could exceed ten billion by the end of this century. Now, a new study has examined what it would take to reverse that unrelenting growth and achieve a sustainable population that is less threatening to biodiversity and ecosystems around the world. Short of a global catastrophe, scientists say, the only way to halt this population momentum is to institute a planet-wide one-child policy within a few decades.

According to recent projections, the number of people living on Earth could exceed ten billion by the end of this century. Now, a new study has examined what it would take to reverse that unrelenting growth and achieve a sustainable population that is less threatening to biodiversity and ecosystems around the world. Short of a global catastrophe, scientists say, the only way to halt this population momentum is to institute a planet-wide one-child policy within a few decades.

The new study comes on the heels of a statistical projection released in September. It analyzed U.N. data from July and calculated how likely population is to end up in different ranges. In particular, it found an 80 percent chance for a population between 9.6 billion and 12.3 billion by century's end, with the most likely figure at around 10.9 billion.

That number is not sustainable, according to Corey Bradshaw, a biologist at the University of Adelaide in Australia.

"Things like forest elephants? Kiss 'em goodbye. Tigers in India? They're gone," Bradshaw told mongabay.com.

Bradshaw and his Adelaide colleague, Barry Brook, examined whether it's possible to rein in population growth in the Proceedings of the National Academy of Sciences. They found that without draconian limits on the number of children per family, population growth is "virtually locked in."

The researchers studied computer models of population over the next century, focusing particularly on how different parameters—or levers—affected their models.

"We're not out there trying to predict there will be X number of people on the planet as of 2100," Bradshaw said. "What we didn't really know is the strength of the different levers one can pull."

Bradshaw and Brook pulled on three levers. First was fertility: the average number of children women have. Next was mortality: the likelihood that people die by a certain age. And the last was primiparity: the average age at which women have their first child. They modeled "what if?" scenarios that adjusted these levers.

Continue reading at ENN affiliate, MONGABAY.COM.

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