Climate Change & Food Monitoring?

From the journal Nature about a study done on maple syrup:

"Human-related carbon emissions may skew isotope analysis for food-quality control."

"We've known that atmospheric carbon isotope values were changing, but nobody was applying this to food science," says geochemist John Valley at the University of Wisconsin-Madison. "Clearly, food-monitoring studies need to start taking atmospheric isotope data into account."
Published online 5 February 2010 Nature doi:10.1038/news.2010.56
http://www.nature.com/news/2010/100205/full/news.2010.56.html