In the last thirty years, the number of cities with a population of over  ten million jumped from 10 to 34. Today, 55% of the world population  lives in a city. And those numbers are only going up, which creates  concerns since megacities face disproportionate effects of climate  change due to their population densities and geographic locations.  Today, we’ll break down some of the many environmental risks facing  megacities, and some strategies to manage them. With special guest Dr.  Madhu Dutta-Koehler: Director of the City Planning and Urban Affairs  program at Boston University.