The U.S. and Mexico will need better land-use planning along their border over the next 20 years to avoid a host of serious environmental ills, according to a new report by a group of U.S. and Mexican universities. The area’s population could nearly double by 2020, straining already dwindling water supplies and worsening cross-border air pollution, the San Diego-based Southwest Center for Environmental Research and Policy found. The border region contains some of the poorest communities in the U.S. and a growing industrial zone in Mexico that is even poorer. In addition to land-use planning, the report suggests greater reuse of water and diversification of local economies through industries such as eco-tourism.