Veggies vary in carbon-footprint impact

Putting blanket labels on crop carbon footprint may be harder than once thought. Although crops absorb a large amount of carbon from the atmosphere, they and surrounding soils also respire a great amount too. Net carbon impact of a crop depends on many factors, including geography, year-to-year variation, fuel used to transport the crop and how much biomass is left after harvest to be returned to the soil. Researchers found, for example, that lettuce is often a net source of carbon. Full story: Planet Earth Online