The commission is negotiating with the global shipping organization, the International Maritime Organization, over various alternatives to reduce greenhouse gases. If there is no solution by year’s end, sea freight will also be included in Europe’s emissions-trading program, said Barbara Helferrich, a spokeswoman for the European Commission’s Environment Directorate. “We’re really ready to have everyone reduce  or pay in some way,” she said.

The European Union, the world’s leading food importer, has increased imports 20 percent in the last five years. The value of fresh fruit and vegetables imported by the United States, in second place, nearly doubled from 2000 to 2006.

Under a little-known international treaty called the Convention on International Civil Aviation, signed in Chicago in 1944 to help the fledgling airline industry, fuel for international travel and transport of goods, including food, is exempt from taxes, unlike trucks, cars and buses. There is also no tax on fuel used by ocean freighters.

Proponents say ending these breaks could help ensure that producers and consumers pay the environmental cost of increasingly well-traveled food.

Image The Sanifrutta company in Italy ships kiwis from its plant in Costigliore Saluzzo, traveling by sea in refrigerated containers. Credit... Massimo Sciacca for The New York Times

The food and transport industries say the issue is more complicated. The debate has put some companies on the defensive, including Tesco, Britain’s largest supermarket chain, known as a vocal promoter of green initiatives.

Some of those companies say that they are working to limit greenhouse gases produced by their businesses but that the question is how to do it. They oppose regulation and new taxes and, partly in an effort to head them off, are advocating consumer education instead.