GRAND RAPIDS -- The collapse of cities, a return to rail transportation, famine and a worldwide depression are but a few outcomes predicted by energy industry insiders and believers in the peak oil theory who gathered this weekend at Calvin College.

"We will have a different civilization, to be sure," said David Goodstein, a vice provost and professor of physics at the California Institute of Technology (Caltech).

Goldstein wrote the book, "Out of Gas: The End of the Age of Oil." He joined dozens of speakers at the International Conference on Peak Oil and Climate Change.

He was the kickoff speaker at the three-day event, which explored the double-pronged crises of peak oil and climate change by examining their effects on society, and offering sustainable solutions.

Peak oil is the point at which half of the world's supply has been extracted and production levels off. This is expected to cause massive societal upheaval because the worldwide demand for oil is increasing rapidly.

It's a controversial subject, and not all are convinced. Skeptics and some oil producers say a peak is years away and that new technologies will allow our energy appetite to be satisfied by tar sands and oil shale while renewable sources come online.

But those who believe in the peak oil scenario say we have reached that point already or will in a few years. New oil discoveries are slim. The last major discovery was in the 1960s.

They say that alternative energies cannot match the capacity of fossil fuels, and nuclear fusion -- the one known silver bullet -- is perpetually 25 years in the future.

Supply will be further constrained by aging infrastructure, they say. These arguments are fueled by the rising cost of food and oil, which recently topped $130 a barrel.

One point that everyone agrees on is that oil is a finite resource, and that nobody quite knows for sure how much is left.

"We will see the effects of the peak very soon. How soon -- I don't know," Goldstein said.

"It's possible that it'll be off another five, 10, or even 20 years.

"But 20 years is nothing on the scale of human history," he said. "Our children, or our grandchildren are in for some very difficult times."

That could mean civil unrest and famine, as petrol-based fertilizers become prohibitively expensive, driving up the cost of food -- and everything else.

"The haves and the have-nots are going to be fighting for diminishing reserves," said Steven F. Crower, an energy investment banker based in Denver.

"I think the price of oil will cause the collapse of the dollar," he said. "The new gold standard is going to be energy."

That's somewhat less dire than the reality painted by Richard Heinberg, an author of eight books on peaking resources and a senior fellow at the Post Carbon Institute.

All complex systems inevitably collapse, said Heinberg, and ours is no different. A local-based agrarian economy is his vision of the future. Rail will be the primary transportation mode.

For some conference attendees, the concept of peaking oil production seemed like a very stark reality.

"I think it was Hunter S. Thompson who said that sometimes the massive crime that takes place in front of everyone is the one that goes unnoticed," said Jackson Carreras, 24, of Plymouth.

The conference was organized by Aaron Wissner, of Middleville, who heads-up the local nonprofit, Local Future. It runs through 5 p.m. today.

Send e-mail to the author: gellison@grpress.com

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