The Comoros claimed the dubious distinction of most threatened, followed by Togo, the Cook Islands, Kiribati, and Eritrea. Other notable countries in the top fifty include Pakistan (8), North Korea (25), China (35), and South Africa (46). The United States did not make the list.

Just how big is this threat? Over a billion people rely on seafood as their main source of protein. Before mid-century, global population is expected to reach nine billion, creating further demand for ocean-based food. Many nations struggling with nutrition will be further challenged, and citizens of some developing nations will likely turn to inferior foods. The authors elaborate:

Losing [seafood] may mean more dependence on less healthy processed foods that are imported from abroad. Communities that have recently made a shift from eating traditional seafood items to importing cheap, processed foods have suffered widespread health problems. For example, in Pacific Island nations about 40 percent of the population has been diagnosed with diabetes, cardiovascular diseases or hypertension.

The combined rankings were based on three factors: exposure to climate change and ocean acidification, rates of seafood and fish consumption, and adaptive ability. It then predicted these conditions into mid-century for each country.

The report also considers the impacts of climate change and ocean acidification separately. The Maldives are the most threatened based solely on climate change predictions. The Cook Islands, which did not fare much better in the combined rankings, came in at number one in the ocean acidification rankings.

Scientists have already observed disturbing trends in ocean acidification and climate change. Since the Industrial Revolution, ocean pH has decreased by roughly 30 percent. The change in pH spells serious trouble for coral reefs and shellfish that rely on calcium to grow. In increasingly acidic waters, less calcium is available.

Read the full story at National Geographic