The grasses are by far the most important family of plants, whether in terms of their economic value, or in terms of ecology. Although the vast natural tallgrass prairies that used to cloak more than 67 million ha of the country are long gone, they have been mainly replaced by other types of grassland, whether corn, or wheat, or some other species in the Poaceae.
The USA has about 1 billion ha of land, and I was curious about how much of that land is currently dominated by grasses, so I combed the records, added up all the figures, and created a graph.
As you can see from the figure above, about 37% of the entire land area of the USA is dominated by grasses. This includes all the natural prairies, rangeland, and pastures. It also includes all agricultural land devoted to grass crops such as rice, wheat, corn, millet, and other grasses. Finally, it also includes that most hated of "grassland", the suburban lawn.
Grasses that are part of the natural landscape, and those that are used as rangeland and pastures make up the majority of the land dominated by grasses (272 million ha), with agricultural areas coming in second (58.5 million ha). Huge amounts of suburbia are also made up of manicured lawns (16 million ha), which suck up water at a prodigious rate, and are so despised by some that anti-lawn movements have actually sprung up.
Sum them all up and you get an amazing number, and no other plant family comes close to the area devoted to grasses in the country. In that sense, the USA really is an Empire of Grass.
References
Milesi C, Running SW, Elvidge CD, Dietz JB, Tuttle BT, Nemani RR (2005) Mapping and modeling the biogeochemical cycling of turf grasses in the United States. Environmental Management 36: 426-438
USDA Charts and Maps
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