Earth 2100

It's an idea that most of us would rather not face -- that within the next century, life as we know it could come to an end. Our civilization could crumble, leaving only traces of modern human existence behind.

It seems outlandish, extreme -- even impossible. But according to cutting edge scientific research, it is a very real possibility. And unless we make drastic changes now, it could very well happen.

Experts have a stark warning: that unless we change course, the "perfect storm" of population growth, dwindling resources and climate change has the potential to converge in the next century with catastrophic results.

In order to plan for the worst, we must anticipate it. In that spirit, guided by some of the world's experts, ABC News' "Earth 2100," hosted by Bob Woodruff, will journey through the next century and explore what might be our worst-case scenario.

But no one can predict the future, so how do we address the possibilities that lie ahead? Our solution is Lucy, a fictional character devised by the producers at ABC to guide us through the twists and turns of what the next 100 years could look like. It is through her eyes and experiences that we can truly imagine the experts' worst-case scenario -- and be inspired to make changes for the better.

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In the history of Earth, there have been five mass extinctions in which at least half the species on the planet disappeared. Scientists believe the extinctions were brought on by natural disasters -- massive volcanic eruptions, rapid climate changes and meteors hitting Earth.

Today, scientists say we are in the middle of a "sixth extinction" -- and for the first time, it's being caused by one species -- us. It seems inconceivable that we could do so much damage to our planet that we actually cause society as we know it to collapse. But historical precedent shows that it is, in fact, a very real possibility.

"Every society that collapsed thought it couldn't happen to them," says Joseph Tainter, an expert in anthropology and societal collapse. "The Roman Empire thought it couldn't happen. The Maya civilization thought it couldn't happen. Everyone thought it couldn't happen to them. But it did."

These populations grew too much and exhausted their resources -- and their climate suddenly changed. People were forced to fight each other for what little was left or face starvation. Entire societies broke down.

"Civilizations in the past have lost the fight," says climatologist Heidi Cullen. "They have collapsed as a result of the inability to deal with several different events going on at once. I think the takeaway is that honestly, we are not that special."