It's not easy to wrap our reasoning around such large figures. By definition, a weed is simply a plant out of place. For instance, a rose in a field of corn IS a weed. Most noxious weed species are not a part of our historical, natural eco-system. With few exceptions, they are not utilized as forage nor as habitat.
Noxious weeds are an introduced blight on our lands.
Although most are not native to the Western United States, they are highly adaptive and thrive here. It is of note that many of these weeds were introduced by our pioneer ancestors who unknowingly utilized contaminated hay or grain as they settled in the West. Regardless of the method of introduction, noxious weeds are here and they are spreading even today. We Encourage you to expand your knowledge about noxious weeds. Visit our local Extension Agent, Ag Inspector, park ranger or federal land manager about specific weed problems in the area.