Tadi had just returned in his dugout canoe from scanning crevices in a nearby reef for octopus. He and his neighbors spend every day this way — scouring the ocean for something to eat or sell. Fishing, here, is about survival.
Their stilt village has no industry, no land, no running water. They dive without oxygen, wearing hand-carved wooden goggles, and carry spear guns hacked from logs with their machetes. They eat what they catch and sell the rest, using the money to buy everything else they need: boat fuel, root vegetables, rice, wood.
Without fishing, “how would I feed my family?” asked Tadi, who like many Indonesians has only one name.
Now Tadi’s community, like countless others across the globe, is on a collision course with the industrialized world’s fossil-fuel emissions.
Hundreds of millions of people around the world rely on marine life susceptible to warming temperatures and ocean acidification, the souring of seas from carbon dioxide emitted by burning coal, oil and natural gas. That includes Northwest oyster growers and crabbers in the frigid Bering Sea, who now face great uncertainty from shifts in marine chemistry.
But from Africa to Alaska, many coastal communities face a substantially greater risk. These cultures are so thoroughly dependent on marine life threatened by CO2 that a growing body of research suggests their children or grandchildren could struggle to find enough food.
The science of deciphering precisely who might see seafood shortages remains embryonic.
But with many of the most at-risk coastal communities already facing poverty, marine pollution, overfishing and rising seas, the potential for calamity is high.
“I can’t tell you how many people will be affected,” said Sarah Cooley, at Woods Hole Oceanographic Institution in Massachusetts, who studies links between acidification and food security. “But it’s going to be a very big number.”
Said Andreas Andersson, an acidification and coral reef expert with the Scripps Institution of Oceanography in San Diego: “These people are literally going to be fighting for their lives.”
Among the most vulnerable to changing ocean conditions are people like Tadi and his 1,600 fellow villagers.
For as long as he can remember, Tadi has netted, trapped, hooked or speared grouper, snapper, wrasses and parrotfish. Sometimes the men in his village disappear to the open sea for days to chase small tuna.
Women swarm the tide flats gathering clams, sea cucumbers, urchins and sea grass. They then paddle to a fish market on nearby Kaledupa Island, where even meaty catches fetch just a few dollars.
The Sama people, or Bajau, are known as sea gypsies or sea nomads because they once lived mostly on boats. They roamed Southeast Asia between Malaysia, the Philippines and Indonesia, living off the sea, until governments began encouraging them to settle. Tadi’s offshore village was built in the late 1950s.
Today, up to a million sea nomads are sprinkled throughout the Coral Triangle.
After centuries of traveling far and wide, the Bajau’s relocation concentrated their human waste and limited the range of their fishing. This happened just as some in their village adopted the destructive practices of Asia’s worst fishing fleets. A few here fish with coral-destroying bombs or cyanide. Some from the village and nearby islands gather colorful reef fish for sale to the aquarium trade. Commercial trawlers from elsewhere cause more damage. It all takes a toll.
“There’s been a pretty substantial decrease in their catches per amount of effort since the 1990s,” said Paul Simonin, a Cornell University graduate student who has tracked Bajau fishing data.
Tadi’s neighbors and nearby island communities still land plenty of fish, but their reefs have seen better days. Everyone works a bit harder to find food.
And a coming storm from CO2 will only make things worse.
Scientists are still navigating the complex ways carbon dioxide can alter the marine world. But some impacts are clear.
Rising temperatures already wreak havoc on corals. Warming waters can cause corals to eject the algae that give them their vibrant color, weakening or killing reefs and turning them white. This process is known as bleaching. Without reductions in global emissions, 90 percent of reefs by midcentury are projected to see severe bleaching episodes every year.
Ocean acidification will just compound the problem.
A quarter of the CO2 spewed by cars and power plants winds up in the ocean. That lowers the pH, makes waters more corrosive and reduces carbonate ions, which then makes it harder for marine creatures to build their shells and skeletons.
Acidification can directly harm animals throughout the food web, from microscopic plankton to some fish. It endangers corals, weakening their skeletons, inhibiting growth, and increasing the likelihood of bleaching. In fact, acidification even accelerates the dissolution and breakdown of the reef.
Together, souring seas and warming can be worse than the sum of their parts.
“Temperature has zapped a lot of reefs so far, but longer-term effects are likely to come from acidification,” said Charles Sheppard, a professor at England’s University of Warwick who studies climate-change impacts on coral reefs.
These ocean changes may not directly hit the octopus and fish Tadi catches, but will almost certainly rearrange the foods available for those creatures to eat. And loss of coral, by itself, usually translates to fewer fish and marine creatures — often substantially fewer.
Earlier this month, researchers working on reefs naturally bathed in CO2 in Papua New Guinea reported finding half as many small invertebrates — crabs, shrimp, sand dollars, marine worms — as on healthy corals.
“Think about a coral reef as a city, a lot of buildings and houses,” Andersson said. “Without the houses, you have no inhabitants.”
Scientists are still learning how much — or how little — marine life might adapt. Some corals appear more resilient than others, and bleaching doesn’t always ruin healthy reefs, said David Kline, a coral and climate change scientist at Scripps.
But reefs across Southeast Asia, in particular, already are a fraction of what they once were, according to a 2007 analysis. And reefs taxed by pollution or overfishing are more susceptible to mat-forming algae. In the worst cases, after bleaching, this weedy slime can smother corals for good.
At least 6 million people in 99 countries fish coral reefs, according to research published in the journal PLOS One in June. Another 400 million or more are tied indirectly to coral. Indonesia alone is home to nearly 1,000 inhabited islands, many of which are filled with people who depend on reefs.
“In the 15 or 16 countries we’ve surveyed, 50 to 90 percent of their protein comes from fish,” said Johann Bell, a fish expert helping Pacific Island nations deal with threats to seafood. “It’s a huge problem. There are going to be many who just fall below the radar.”