Distribution centers near the nation's top seaports are bursting with consumer goods and other cargo - and that's before the Panama Canal extension opens next spring. Distribution center and warehouse occupancy levels have reached historic highs, while expensive construction and labor costs keep new development sparse in many seaport industrial real estate markets.

Import volume at the nation's major retail container ports is expected to increase 3.3 percent in May over the same month last year, but growth could trickle to a standstill by the end of the summer, according to the monthly Global Port Tracker report released by the National Retail Federation and Hackett Associates.