Read: Banaskantha is a dry region where cattle herders have long lived a nomadic or semi-nomadic life. Some move their herds all year round; others leave their village only when there isn't enough to keep going. The first group moves by choice. The second, and far larger, group moves only when it must. With little land of their own, poor herders depend on shared village land for grazing, which is usually poorer than private land. In a dry place its grass and fodder run out quickly, and the more families that depend on it, the faster it is used up. When it is grazed bare, the poorest families are forced to move to where there is more grass. Without enough feed, their animals give less milk and the herders earn less; in a drought, they risk losing not just income for a while but their income and assets for good. Why are the poor herders of Banaskantha forced to migrate?