Debate over the environmental impact of food miles racked up by organic produce has raged in Europe recently, where the UK's Soil Association has put forward the possibility of barring foods transported by air freight from being labelled as organic.
Awareness of the issue on both sides of the market could engender a re-think of organic supply infrastructure - just when consumer awareness is taking off and the market is growing.
According to British consultancy Organic Monitor, the global organic food and drink market was projected to generate revenues of US$40 bn in 2006. In North America the market has received considerable boost from the establishment and growth of natural and organic retailers such as Whole Foods Market.
Researchers from the Department of Rural Economy at the University of Alberta in Edmonton, Canada, collected data on organic produce from six grocery stores in the Edmonton area and interviewed suppliers about their shipping methods.
They found that most of the fruit and vegetables brought into the area travel by truck, a mode of transportation that has increased since the 1970s, while more energy efficient rail and water transportation has fallen out of favour.
What is more, organic produce tended to travel from further afield than conventional produce.
Researcher Vicki Burtt said: "If you're buying green, you should consider the distance food travels. If it's travelling further, then some of the benefits of organic crops are cancelled out by the extra environmental costs."
For instance, organic mangoes were seen to have been shipped from Ecuador and Peru, rather than Mexico for conventional mangoes; and peppers tended to come from Mexico rather than the US or Canada.
Burtt and team calculated that the annual environmental cost for a city the size of Edmonton for transporting organic produce was C$156,000 to $175,000, or 6,348 to 7,124 tonnes of carbon dioxide.
The comparable cost for conventional produce was C$135,00 to $183,000, or 5,492 to 7,426 tonnes of carbon dioxide.
When they looked at the price difference between organic and conventional produce, the researchers "found that a large gap between total costs to the consumer and the price paid in the store for organic produce indicates that retailers could cover the environmental costs without passing those costs on to the consumer".
Publication details of the study were not available, and the full methodology and have not been seen by FoodNavigator-USA.com.
When it comes to organic dairy produce, market researcher Organic Monitor said this week that there is considerably more organic milk available on the US market than previously, as farmers completed the transition process ahead of new regulations.
This is reducing the amount of organic dairy transported into North America, from as far afield as Australia and New Zealand.