One of the most potentially disastrous consequences of global warming is likely to be the massive migration of displaced populations, including many of the world's poorest. As a place where a wealthy, heavily industrialized country is bordered directly by a struggling, preindustrial nation, the 2,000-mile United States-Mexican border provides a stark preview of the challenges we will face. Stereotyped thinking, based on racism or fear, will not solve these problems. The Golden Door