Change is inevitable. The best we can do is manage it to protect the most vulnerable people affected by it. In the past this meant the poor and the elderly, but increasingly it’s also coming to include the young—kids recently graduated from college, and young families who can’t find an affordable place to live. Helping these people is going to involve building a lot of new real estate, some of it potentially ugly, taller, and in much higher density than many neighborhoods have seen before. But when, as a society, we have to choose between architectural preservation and giving people a roof over their head, the choice is clear: we should preserve the best buildings and blocks and bulldoze the worst to make way for the future.