North American Cropland - Code: Ne13B

Human activities have altered the landscape of North America for thousands of years but few have had as much of an impact as modern agriculture. Croplands, or areas that are dedicated to the cultivation of specific species of plants for human use, are the largest form of landcover in North America. Croplands account for ~45% of the terrestrial area of the United States and ~60% of Mexico. The arable areas in Canada are much more restricted due to high latitudes, soil and topography, only accounting for 7% of the country by area.
Land-clearing, controlled burns, irrigation, fertilization and other landscape altering techniques that favor agriculture have been used in North America for thousands of years. While most commercially produced crops from the Americas originated with the huge civilizations found in central and southern Mexico, hundreds of other species were cultivated across the continent both in small farms, gardens, and through selective forestry. Beginning in the 18th century, Europeans began clearing huge forested areas both for timber and agricultural production. Areas of especially productive soils were nearly completely converted to agriculture and prized land that was once Tallgrass Prairie and California Grassland is now almost entirely cropland. Most farms until the 20th century were small and diverse with many species and cultivars being grown on a single plot of land. These farms were often divided with hedgerows and woodlots that provided shelter for wildlife in agricultural settings.  Since 1900 the trend has rapidly moved to fewer, larger, and less diverse farms. In the last century the number of farms in the United States and Canada has fallen by 63 percent, while the average farm size has risen 67 percent. A similar trend has occurred in Mexico, though the number of small, diverse farms remains much higher.
The vast majority of cropland in North America is devoted to cereal crops – principally corn, sorghum, wheat, and barley. Soybeans, cotton, potatoes, beets, and rice also account for a large amount of the acreage in cropland. In Mexico the diversity of climate and relatively warm temperatures mean most cereal production occurs on the Chihuahuan Plateau, except for corn which is grown throughout. Mexico has a more diverse set of commercially produced crops including many orchard species like oranges, limes, mangoes, and avocados. Coffee is also a commercially important crop in Mexico and on Hawaii. Cropland varies wildly in terms of quality of habitat for wildlife. Many row crops like soybean and corn can be virtually devoid of animals. Others like rice fields can be filled with a variety of birds, especially when fallow. A few of the various crops grown on the continent are covered below.
Corn or Maize (Zea mays) takes up more land mass than any other crop on the continent, with over 115 million acres (47 million ha) devoted to cultivation. This freakish member of the grass family has been selectively bred to produce massive fruits made of hundreds of small kernels. Corn is typically planted in extremely tight rows and mature plants grow to 10ft (3m). It is an annual crop, harvested once a year. Corn fields are generally fallow in the winter months.
Rice (Oryza sativa) is the most important cereal crop on the planet but is produced in relatively small areas of North America. A wetland species, rice is grown in paddies or flooded fields in low-lying areas with mild winters. Most rice production on the continent occurs in the central valley of California, along the Gulf of Mexico and in the Mississippi River Valley. Rice is harvested once a year in most of the continent and generally cultivation takes place in areas that were formerly wetlands.
Coffee (Coffea arabica and C. robusta) is an evergreen shrub that is grown at mid-elevations in central and southern Mexico as well as Hawaii. Traditionally this small shrub was cultivated as an understory plant in the shade of remnant forest trees or under planted shade trees. Starting in the 1970s production largely shifted to coffee grown in open areas with full sun. Sun coffee shrubs grow more quickly and the berries also ripen faster, however the method requires more extensive forest clearance as well has larger amounts of water, fertilizer, and pesticide.  Currently about 25% of the world’s coffee is shade grown though there has been a major push in favor of shade-grown coffee in recent years as this form of production maintains some valuable wildlife habitat and is less environmentally damaging.