From the CO2Science archive: Barnyard grass aka Echinochloa crus-galli (L.) Palib.is a weed if what you want to grow are food crops, or forage if what you want is to feed livestock. But like it or hate it, it benefits from more CO2. From 1985 to 2011 there were 8 experiments reporting an average 24.4% boost in photosynthesis from an extra 300 ppm CO2 in the air.