長文読解（人文系・自然科学系の文章）- 問題85

Ocean acidification, often called "the other CO2 problem," has emerged as one of the most pressing environmental challenges of our time. As the ocean absorbs approximately 30% of human-produced carbon dioxide, seawater becomes more acidic, fundamentally altering marine chemistry. Since the Industrial Revolution, ocean pH has dropped by 0.1 units, representing a 26% increase in acidity.
This chemical change poses severe threats to marine ecosystems, particularly organisms that build calcium carbonate shells and skeletons. Coral reefs, which support 25% of all marine species despite covering less than 1% of the ocean floor, are especially vulnerable. Studies show that many coral species struggle to maintain their skeletal structure in increasingly acidic waters.
The economic implications are equally alarming. Coastal communities worldwide depend on healthy marine ecosystems for fishing, tourism, and coastal protection. Scientists estimate that ocean acidification could cost the global economy billions of dollars annually through reduced fisheries productivity and coral reef degradation. Immediate action to reduce carbon emissions remains the most effective strategy to address this invisible crisis threatening our oceans.