Improve Marine Aquaculture Conditions Before It’s Too Late

Enlarge Image Image Gallery In “The Ocean of Life,” author Callum Roberts explores the history of mankind’s exploitation of the seas, including the impact modern fishing techniques, pollution and climate change, and reveals what it would take to preserve world’s waters for future generations. Cover Courtesy Viking

The first time water rushed onto your toes, your feet buried in the sand, you couldn’t imagine the magnitude of the ocean or all that it held. In Callum Roberts’ vibrant book, The Ocean of Life (Viking, 2012), take a fascinating tour of the history of mankind’s relationship to the sea, from the course of currents first discovered by Benjamin Franklin to the effects of shrimp farming in present-day China. In the last 20 years we have transformed the oceans beyond recognition — and not for the better. Find out how current marine aquaculture conditions harm coastal ecosystems and what we can do to prevent further damage. This excerpt is taken from Chapter 16, “Farming the Sea.” 

The explosion of marine fish farms across the world has transformed coasts, estuaries, and deltas in dozens of countries. China has pursued one of the most aggressive aquaculture development programs of recent years. In 2003, marine aquaculture covered nearly six thousand square miles, about half of China’s twenty-thousand-mile coastline. Most of these farms were carved out of mangrove forests, mud flats, salt marshes, and sea grass beds. Satellite photographs of the Bohai Sea coast, one of the most intensively farmed regions, show the toll taken. Straight-edged ponds incised in blue and turquoise pack the coast to depths of a couple of miles inland, and crawl seaward across mud flats. The Philippines and Vietnam have lost three quarters of their mangrove forests in the last few decades, half of them to aquaculture. Sadly, many of these ponds have been abandoned. When mangrove soils are exposed to the air, they become acidic. The acid leaches into pond water together with toxic quantities of aluminum, so the ponds cannot be used unless they are lined.

Mangroves and salt marshes are self-repairing buffers that defend coasts against storm and flood. If they remain healthy, there is a good chance they could also ameliorate the worst effects of sea-level rise by trapping sediment and building upward. In many places aquaculture has not only removed this benefit, it has caused the land to sink by sucking freshwater from belowground to create brackish ponds for shrimp and milkfish.