Spanish, Mexican, and American settlers required open expanses of land for agriculture and ranching, displacing indigenous inhabitants. The high poverty traditionally felt by many residents, combined with San Antonio's environment, has contributed to the development of the city's unusually complex public health dilemmas. The national drive to preserve historic landmarks and landscapes has been complicated by the blight of homogenous urban sprawl. But no issue has been more contentious than that of water, particularly in a city entirely dependent on a single aquifer in a region of little rain. Managing these environmental concerns is the chief problem facing the city in the new century.