Through the Billion Oyster Project, leftover shells from more than 45 New York restaurants are cleaned, cured in the sun, 'set' with microscopic larvae and redeployed in bags all around the city’s waters. The shells - 1.8 million pounds to date - offer a home for baby oysters and will ultimately build a reef. The oyster reefs that once made up more than 220,000 acres of New York’s coastline were disrupted by the commercial oyster industry, but human engineering is helping rebuild that natural flood-mitigation system. The $60-million Living Breakwaters project is a mammoth reef being built off Staten Island. Coastal communities in Texas, Louisiana, and California also are carrying out oyster restoration but for biodiversity, pollution-filtration and economic reasons — rather than flood-mitigation.