As the oceans absorb more carbon dioxide, the chemistry of the ocean changes, putting many sea creatures at risk. The IPCC projects that by 2100 the pH of the ocean will drop to its lowest point in at least 20 million years. This means that tiny creatures at the bottom of the ocean's food chain will struggle to make their calcium-carbonate shells. Nearly every sea creature from plankton to whales would be directly or indirectly affected. If the ocean food chains collapse, many people in the world who depend on fish for food will go hungry, and seafood may become a delicacy that only the wealthy can afford.