"This is not inevitable," said lead study author Mathew Burrows. "In most cases, it's manageable if you take measures ... now."
Such steps could include decreasing wasting resources like water and increasing the efficiency of food production, he said.
Technology is seen as a potential savior to head off some of this conflict, boosting economic productivity to keep pockets filled despite rising populations, rapid growth of cities and climate change.
Hand in hand with technology is cooperation between the competing states, the authors say. In the most plausible best-case outcome, the report said, "China and the U.S. collaborate," heading off global competition for resources that can lead to all-out conflict.
The report warns of the mostly catastrophic effects of possible "Black Swans," extraordinary events that can change the course of history. These include a severe pandemic that could kill millions in a matter of months and more rapid climate change that could make it hard to feed the world's population.
Two positive events are also listed, including "a democratic China or a reformed Iran," which could bring more global stability.
One bright spot for the U.S. is energy independence.
"With shale gas, the U.S. will have sufficient natural gas to meet domestic needs and generate potential global exports for decades to come," the report said.
On the web: www.dni.gov/nic/globaltrends
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