Urbanization has paradoxically led to higher living standards and, at the same time, environmental degradation that threatens the well-being of people and other species. Urban development has resulted in a host of negative environmental consequences: water pollution, “ozone action days” where it is dangerous for some people to go outside, neighborhoods that experience high levels of asthma and other diseases, and species and habitat destruction. People of color and low-income communities are disproportionately burdened by these environmental and health hazards. They also tend to have less access to parks and other environmental amenities. Environmental justice, sustainability, and climate change adaptation have become critical urban issues that require action at multiple scales. Each urban revitalization initiative is an opportunity to improve local environmental quality and move towards a systematic transformation.