It is often more environmentally friendly to rehabilitate existing structures and maintain and improve existing infrastructures than to simply destroy and replace them. Each existing building is an investment of energy, time, and resources. If these structures are just destroyed that investment is wasted. Also, active historic preservation efforts can help to curb some of the detrimental environmental effects of suburban sprawl, including increased traffic patterns, energy consumption, and environmental degradation. By safeguarding the historic cores of towns and cities and encouraging reinvestment in them, many adverse effects of growth can be greatly reduced.