📚 How to solve these questions: 12 tips for all 6 Interactive Reading question types, with a worked example for each.
The ocean absorbs about a quarter of the carbon dioxide people release, which sounds like good news and is only half of one. The gas does not simply disappear into the water. It reacts, and the result is that seawater has become measurably more 1 over the last two centuries. For most large animals this change is a slow inconvenience. For anything that builds a shell it is closer to a 2 problem. Shells and coral skeletons are made of calcium carbonate, and more acidic water makes that material harder to form and easier to 3. Laboratory work on young oysters shows them growing thinner shells and dying at higher rates. The effects are not spread 4. Cold water holds more gas, so polar seas are changing fastest, and coastal areas that already receive fertilizer runoff are worse again. This unevenness makes prediction difficult, because a species that copes in one region may be in trouble a thousand kilometers away. What makes acidification awkward politically is that it cannot be solved locally. A country can clean its own rivers and protect its own reefs, and many have. Nothing about that changes the chemistry of the water arriving from 5, which depends entirely on how much carbon the world as a whole puts into the air.