The ocean is so acidic that it is dissolving the shells of our baby oysters,” says Diani Taylor of Taylor Shellfish Farms in Shelton, Washington. She and her cousin Brittany are fifth-generation oyster farmers, and are grappling with ocean waters that are more acidic and corrosive than their fathers, grandfathers, and great-grandfathers knew.

This “ocean acidification” is one planetary response to humans’ burning of fossil fuels, which releases carbon dioxide that is absorbed by the oceans. According to the National Climate Assessment, oceans currently absorb about a quarter of human-caused carbon dioxide emissions to the atmosphere, leading to ocean acidification that will alter marine ecosystems in dramatic yet uncertain ways. To learn more about ocean acidification, go to NCA2014.globalchange.gov