WASHINGTON (Reuters) - Environmental degradation and waning natural resources threaten U.S. security in the 21st century, in a shift from “kinetic” security threats, defense experts told a Capitol Hill briefing Wednesday.

The loss of renewable natural resources, including forests, fresh water, fish and fertile soils, can drive political instability and conflict in the developing world, according to the briefing.

“We can’t just send in the Army and the Marines and the Air Force and the Navy to resolve these problems, and they can’t all be security problems,” said retired General Anthony Zinni, former chief of U.S. Central Command.

“Whether it is climate change, whether it is disruption of the environment in other ways ... we’re going to see more failed and incapable states.”

Zinni cited a report from the non-profit Center for a New American Security that linked depletion of fish stocks off Somalia, the drop in water and oil resources in Yemen, frequent droughts in Afghanistan and scarce and polluted water in Pakistan to instability and security.

Lieutenant Colonel Shannon Beebe, a senior Army Africa analyst, contrasted the traditional threats to U.S. and global security with those posed by environmental woes and natural resource problems. He noted that he offered his personal opinion, not that of the U.S. Defense Department.

“An American security narrative is very much based on the kinetics ... planes, tanks, guns, armed forces,” Beebe said, saying these kinetic threats would be replaced by “creeping vulnerabilities.”

“You think we’re going to continue to face state-based threats?” he asked rhetorically. “Might I remind you of the two greatest attacks on the United States at the beginning of the 21st century, and neither of those was from a state-based threat: 911 and Hurricane Katrina.”

Both men cited their own experience in the Europe, Asia and Africa with defense leaders who recognized that integrating environmental problems into security policy was essential. Beebe said the United States has yet to understand that a coordinated narrative on this is key.

“When you talk to Africans ... ministers and chiefs of defense, they will talk to you in terms of security as food, as environmental degradation, natural disasters, environmental shocks,” Beebe said.

“Until we get the narrative correctly, it’s going to be a lot like putting an American baseball umpire at a cricket match and expecting the outcome to be positive,” Beebe said.