Rising incomes in developing parts of the world are allowing millions of people to transition from subsistence diets consisting of mainly grains to those including beef. This dietary shift is accelerating the demand for grain around the world at a rate that is "much greater than the world's farms can produce," and that is contributing to higher grain, land and food prices. Similar forces are driving energy prices higher. "Global energy consumption has doubled in the past 50 years, paralleling demand for food," Tilman said, explaining that it will double again in the next 40 years.