Fields of carrots are watered March 29, 2015, in Kern County, Calif. Subsidized water flowing in federal and state canals down from the wet north to the arid south helped turn the dry, flat plain of the San Joaquin Valley into one of the world's most important food-growing regions. Frederic J. Brown/AFP/Getty Images hide caption

itoggle caption Frederic J. Brown/AFP/Getty Images

Humans have influenced Earth's history for thousands of years, though some scientists count changes of the last two centuries as especially notable. (Left to right) Universal History Archive/UIG via Getty Images; Hulton Archive/Getty Images; Liszt Collection/Heritage Images/Getty Images; Joint Task Force One/AP hide caption

itoggle caption (Left to right) Universal History Archive/UIG via Getty Images; Hulton Archive/Getty Images; Liszt Collection/Heritage Images/Getty Images; Joint Task Force One/AP

These beans, grown on test plots at the International Center for Tropical Agriculture in Colombia, can thrive in temperatures that cripple most conventional beans. Courtesy of CIAT/Neil Palmer hide caption

itoggle caption Courtesy of CIAT/Neil Palmer

The European Union banned the use of antibiotics to boost animals' growth in 2006. At first, the ban had little effect on the amount of drugs given to pigs. Carsten Rehder/Corbis hide caption

itoggle caption Carsten Rehder/Corbis

A field of unharvested wheat is seen in Ashby-de-la-Zouch, England, in 2012. Wheat wasn't cultivated in Britain until some 6,000 years ago, but DNA evidence suggests early Britons were eating the grain at least 8,000 years ago. Darren Staples/Reuters/Landov hide caption

itoggle caption Darren Staples/Reuters/Landov

Tim Meyers on his four-acre vegetable farm in southwestern Alaska. Behind him: an endless sea of tundra, and a glimpse of the town of Bethel. Eugenie Frerichs for NPR hide caption

itoggle caption Eugenie Frerichs for NPR

Arctic Granny (right), a GMO variety created by Okanagan Specialty Fruits, got the gren light from federal regulators Friday. The apple doesn't turn brown like a conventional Granny Smith apple (left). Okanagan Specialty Fruits hide caption

itoggle caption Okanagan Specialty Fruits

In 2013, the U.S. imported about 2 million tons of Coronas and Modelos, making beer Mexico's largest agricultural export to the U.S., according to a USDA report. Scott Olson/Getty Images hide caption

itoggle caption Scott Olson/Getty Images

The drought forced many citrus farmers near Orange Cove, Calif., to mulch their trees because they couldn't afford to keep them alive. Recent rain and new groundwater regulations have eased the crisis, but only slightly. Kirk Siegler/NPR hide caption

itoggle caption Kirk Siegler/NPR

Like many beginning farmers, Grant Curtis wants to invest in his operation, but expectations of low prices are tying his hands. Abby Wendle/Harvest Public Media hide caption

itoggle caption Abby Wendle/Harvest Public Media

A global positioning receiver on the top of a combine harvester at a farm in Warwick, Md., in June. The equipment uses sensors and computers to help drive the combine along the route where the crops were planted, judge the composition of a crop and generate crop yield reports. Brendan Smialowski/AFP/Getty Images hide caption

itoggle caption Brendan Smialowski/AFP/Getty Images

California sheep rancher Dan Macon had to sell almost half of his herd because the drought left him without enough feed. Kirk Siegler/NPR hide caption

itoggle caption Kirk Siegler/NPR

Pinatas are among the new generation of club apples — varieties that are not just patented, but also trademarked and controlled in such a way that only a select "club" of farmers can sell them. Stemilt Growers LLC hide caption

itoggle caption Stemilt Growers LLC

Sunlight streams into a corn storage building at a Michlig Grain storage facility in Sheffield, Illinois, U.S., on Oct. 31, 2014. The price of corn has been falling for months. Daniel Acker/Bloomberg via Getty Images hide caption

itoggle caption Daniel Acker/Bloomberg via Getty Images

Farms outside Baghdad as seen from a U.S. Army Blackhawk helicopter. Much of Iraq's soil has a high salt content because of flooding and poor drainage. Jim Gordon/U.S. Army Corps of Engineers/Flickr hide caption

itoggle caption Jim Gordon/U.S. Army Corps of Engineers/Flickr

The Illinois State Corn Husking Competition is one of nine competitions happening during harvest season all across the Midwest. Abby Wendle /NPR hide caption

itoggle caption Abby Wendle /NPR

Paul Herringshaw says farmers like him have been taking steps to reduce crop runoff for years. Sarah Jane Tribble/WCPN hide caption

itoggle caption Sarah Jane Tribble/WCPN

Jeff Jones and his daughters feed grain to their foraging cattle once a day in Callaway County, Mo. They're concerned about the health and environmental effects a potential hog farm next door might have. Kristofor Husted/KBIA hide caption

itoggle caption Kristofor Husted/KBIA

Sam Van Aken's grafted fruit trees are still quite young, but this artist rendering shows what he expects the "Tree of 40 Fruit" to look like in springtime in a few years. Courtesy of Sam Van Aken hide caption

itoggle caption Courtesy of Sam Van Aken

More than 170 volunteers in the Brattleboro, Vt., area have contributed urine to the Rich Earth Institute field trials. Mike Earley/Courtesy of Rich Earth Institute hide caption

itoggle caption Mike Earley/Courtesy of Rich Earth Institute