Your browser does not support inline frames or is currently configured not to display inline frames. Content can be viewed at actual source page: http://youtu.be/hlbMzDQRSqE

The Earth's population has nearly doubled in the last 100 years. Add climate change, lack of land to grow food and overconsumption to the mix and life as we know it on the planet appears to be in peril.

Is there a limit to the number of human beings the Earth can sustain? And if there is, are we getting close to that number?

One of the world's leading experts on population growth is speaking at San Diego State University on Wednesday. It's a sensitive topic for many people and nations, but the growth of human population may also be the most important topic facing the future of the human race.

Ryerson told KPBS that the United Nations estimates our population will be between 8 billion and 10.1 billion by 2050. There are currently about 7 billion people on the planet.

He said energy consumption and water are major concerns as our population continues to rise.

"The top-three grain producing countries of the planet, India, China are the United States, all have unsustainable pumping for irrigation," he said. "And water tables are sinking in these countries dramatically. In India, the water table is sinking by about 10 feet a year. And more and more farms are turning to desert as farmers can no longer reach the water, there are about 150 million people in India now being kept alive through unsustainable pumping of underground aquifers. When that water returns out, those people will face immediate starvation."

Ryerson said he calls attempts to boost conservation and efficiency "greening the Titanic."

"In reality, the problem we have is not climate change, it's not water shortage, it's not loss of biodiversity, it's not degradation of soils," he said. "It is overuse of the Earth's resources by the human endeavor."

But population control is a sensitive issue, Ryerson said. He said China's one-child policy has been a "black eye" for the topic.

"People suddenly started associating the concern with coercion," he said. "In fact, in China, much of what they accomplished has been done through persuasion."

Claire Trageser contributed to this report.

FEATURED PODCAST KPBS' daily news podcast covering local politics, education, health, environment, the border and more. New episodes are ready weekday mornings so you can listen on your morning commute.





Sign up for Today's Top Stories newsletter Need help keeping up with the news that matters most? Get the day's top news — ranging from local to international — straight to your inbox each weekday morning. Enter your email address

KPBS Midday Edition is a daily radio news magazine keeping San Diego in the know on everything from politics to the arts.

To view PDF documents, Download Acrobat Reader.