Grasses and legumes that make up grasslands and are used as forages for livestock. The grasslands represent an ancient renewable natural resource. They form 25% of the world's vegetation and occupy the largest area of any single plant type. They benefit humanity indirectly by providing food for both wild animals and domesticated livestock, some of which are ruminants that, because their digestive systems contain microorganisms, are able to digest fibrous forage material. Thus, the prime value of grassland areas lies in the meat, milk, or work produced by the livestock that graze on them.