WASHINGTON --- Regional conflicts driven by competition for food, water and energy, increased urbanization and the possibility that nonstate actors could obtain high-tech components for enhancing lower-tech weapons are among the global challenges U.S. joint military leaders likely will face over the next quarter-century, a senior officer said here today.>> These scenarios are part of the Joint Operating Environment 2008 report recently issued by Norfolk, Va.,-based U.S. Joint Forces Command, Navy Rear Adm. John M. Richardson told American Forces Press Service and Pentagon Channel reporters.>> The report outlines potential threats and opportunities U.S. joint forces may confront during the next eight to 25 years, said Richardson, JFCOMs strategy and policy director.>> While the nature of warfare will not change, the character of future joint military operations is going to change, Richardson said, as the strategic landscape changes, as the enemy adapts, as new technologies come on, as resources become more scarce.>> The report states that 5 billion of the 8 billion people of the world in the 2030s likely could live in cities, Richardson said. Such a circumstance, he said, increases the opportunity for conflict. Joint warfighters, therefore, should be studying the challenges of carrying out military operations in densely-populated cities, he said.>> Conducting military operations in urban environments is different and challenging, Richardson said, because enemies can blend in among the population and unintended civilian casualties are more likely.