Contributed by: Don WinnerLA Times Blogs Ronald D. White reports: The slowdown in international trade has left the docks at the nation's biggest seaport complex quieter than they've been in years. Some workers, particularly non-union "casuals," at the Los Angeles and Long Beach ports wait for shifts that never come. Automobiles and other merchandise pile up as consumers dig in for a long economic winter. But the problems at the twin ports, along with smaller West Coast harbors, extend beyond the nation's economic woes, maritime experts say, and changes on the horizon could leave the seaports struggling to keep customers. That's the assessment of a recent report by London-based Drewry Supply Chain Consultants, a maritime industry research firm that has about 3,000 clients in more than 100 countries. West Coast ports will see increased competition from the Panama Canal, which is undergoing a bigger-than-expected expansion due to be completed in 2014, Drewry said. In addition, rising Chinese labor costs will push some manufacturing back to Mexico and South America.