1. Beef

Beef is by far the biggest contributor to deforestation, both because of its direct role in forest clearing as well as the land converted for cattle feed, according to Rhett Butler of Mongabay, a kickass site for environmental reporting around the world. Despite efforts to combat deforestation through illegal logging, the Amazon is actually losing forest cover faster than ever, largely due to the cattle industry, which has been growing in Brazil by an average of 3 million head per year since 1974.