evidence: Depopulation, along with aging infrastructure systems, creates social, economic and policy challenges7. In particular, population loss in already developed cities can result in underutilized infrastructure with poor maintenance, possibly leading to disruptions in basic services like transit, clean water, electricity and internet access8,9. Having an estimation of future population trends can assist authorities in better planning and designing cities and their infrastructure systems for depopulation. [...] The solutions to address the challenges brought by depopulation will need to be tailored to local contexts. For example, city size has a large impact—solutions for urban cities rarely apply to rural areas. The type and size of some of the legacy infrastructure that must be maintained are important too, as are local climate and economic conditions. New practices that embrace principles of adaptability, modularity and multifunctionality should be investigated and developed. In the US context, this would also require more flexibility in administrative and financial decision-making. What is certain is that an important cultural shift in planning and engineering communities is needed, away from conventional, growth-based planning, to accommodate a dramatic demographic shift.