National Geographic : 2011 Apr
CASTELLO ARAGONESE IS A TINY ISLAND that rises straight out of the Tyrrhenian Sea like a tower. Seventeen miles west of Naples, it can be reached from the somewhat larger island of Ischia via a long, narrow stone bridge. e tourists who visit Castello Aragonese come to see what life was like in the past. ey climb---or better yet, take the elevator---up to a massive castle, which hous- es a display of medieval torture instruments. e scientists who visit the island, by contrast, come to see what life will be like in the future. Owing to a quirk of geology, the sea around Castello Aragonese provides a window onto the oceans of 2050 and beyond. Bubbles of CO rise from volcanic vents on the sea oor and dissolve to form carbonic acid. Carbonic acid is relatively weak; people drink it all the time in carbonated beverages. But if enough of it forms, it makes BY ELIZABETH KOLBERT PHOTOGRAPHS BY DAVID LIITTSCHWAGER seawater corrosive. "When you get to the ex- tremely high CO , almost nothing can tolerate that," Jason Hall-Spencer, a marine biologist from Britain's University of Plymouth, explains. Castello Aragonese o ers a natural analogue for an unnatural process: e acidi cation that has taken place o its shore is occurring more gradually across the world's oceans, as they ab- sorb more and more of the carbon dioxide that's coming from tailpipes and smokestacks. Hall-Spencer has been studying the sea around the island for the past eight years, care- fully measuring the properties of the water and tracking the sh and corals and mollusks that live and, in some cases, dissolve there. On a chilly winter's day I went swimming with him and with Maria Cristina Buia, a scientist at Italy's Anton Dohrn Zoological Station, to see the ef- fects of acidi cation up close. We anchored our boat about 50 yards from the southern shore of 7 SEVEN BILLION SPECIAL SERIES SEVEN BILLION is a yearlong series on global population.