U.S. researchers say fears of running out of oil are unwarranted, as the demand for oil -- but not the supply -- will reach a peak and then decline.

Warnings of "peak oil" paint pictures of calamitous shortages, panic and even social collapse as the world reaches its peak of oil production and then supplies fall, but researchers at Stanford University and the University of California-Santa Cruz say such scenarios are not likely.

Instead, they said, the historical connection between economic growth and oil use will eventually break down because of limits on consumption by the wealthy, better fuel efficiency, lower priced alternative fuels and the world's rapidly urbanizing population.

"There is an overabundance of concern about oil depletion and not enough attention focused on the substitutes for conventional oil and other possibilities for reducing our dependence on oil," Adam Brandt, a Stanford professor of energy resources engineering, said.

Writing in the journal Environmental Science & Technology, the researchers said a variety of mechanisms could cause society's need for oil to begin declining by 2035.

The report cited studies suggesting passenger land travel has plateaued in industrialized countries and is no longer tied to economic growth. Such travel now accounts for about half of the global transportation energy demand.

Even in developing countries, the researchers said, economic growth has been less oil-intensive than was experienced in the West during the past century.

"We've seen explosive growth in car ownership in countries such as China," UC Santa Cruz environmental studies Professor Adam Millard-Ball said. "However, those cars will be more efficient than those of the past, and travel demand will eventually saturate as it has in rich countries such as the United States."

Price-competitive alternatives to conventional oil are another factor behind the predicted peak in demand, researchers said, including increasing quantities of fuel from oil sands, liquid fuels from coal, natural gas, biofuels, hydrogen and electricity generated from renewable sources.

That does not mean a future free of worry, they said, as various alternatives to conventional oil raise concerns of their own.

"If you care about the environment, you should care about where we are getting these fuels, whether we use the oil sands or biofuels," Brandt said. "Our study is agnostic on what mix of oil substitutes emerges, but we do know that if we don't manage them well, there will be big consequences."