Today, half of the world’s people live in cities. By 2050, three out of four people will be urban residents. This rapid growth is straining the infrastructure that makes cities livable, including roads, water treatment plants, levees and seawalls. By current estimates, the world’s cities will need to invest $5 trillion in upgrading urban infrastructure by 2030 just to keep pace with growth. Natural infrastructure solutions help cities cost-effectively solve challenges of water pollution, drinking water source protection, air quality and climate and disaster resilience while ensuring a healthy, sustainable and prosperous urban future.