 The Tibetan plateau is at a high altitude and has a very cold, dry climate. Over much of Tibet, the only form of food production possible is nomadic pastoralism, with sheep and yaks as the major sources of food. Moreover, under premodern conditions, and given the cold weather, people living in Tibet needed to eat calorie-dense food in order to survive. A strict vegetarianism was therefore quite impractical. As a result, many Tibetans came to accept meat eating as a necessary part of their lifestyle. Today, however, with more vegetarian food options available and with many Tibetans living in exile, important spiritual leaders in the Tibetan tradition have begun to advocate a switch to a vegetarian diet.