Just south of Rome lie the Pontine Marshes, a vexed part of the Italian countryside. In ancient times, Roman emperors tried unsuccessfully to drain the marshes, something only achieved in the 1930s through a system of massive pumps and canals that removed enough water to turn the area into productive farmland. Yet today those canals have become heavily polluted, endangering the area’s agriculture and the health of its residents.
The conventional way of tackling the problem would be to build a series of large water-treatment plants in the area, which covers about 300 square miles. But Alan Berger, an associate professor of urban design and landscape architecture at MIT, has another idea. Because some plants absorb pollutants as water flows by them, carefully designed wetlands can clean up the countryside while preserving its natural feel and providing public park space.