Just south of the U.S. border along Mexico's west coast lies a swath of the Sonoran Desert that defies expectation. It was here, almost 50 years ago, that the green revolution was born when agricultural scientist Norman Borlaug bred a bountiful and scrappy form of wheat that was eventually adopted the world over, earning him the Nobel Peace Prize because it staved off famine and dramatically increased harvests. Thanks to sturdier hybrids and water diverted from nearby rivers, wheat and corn have replaced stands of cacti and made portions of this bone-bleaching desert as lush and verdant as the American Midwest. And now the Sonoran is looking even less like a good desert should. It is turning blue. Last October, Stanford University economist Rosamond Naylor spent four hours flying over the southern part of the state of Sonora, which is half desert, half Sierra Madre mountains, in a crop-dusting plane borrowed for the outing. She was looking for evidence of inland shrimp farms, a burgeoning industry, and expected to find clusters of scattered ponds separated by huge tracts of sere land. Instead, it looked as if the Sea of CortŽs had risen and swept across more than 42 square miles of the Sonoran: everywhere patches of blue, pools of shrimp, one after another, all down the coast. "It was so much more developed than I had thought," Naylor says. "The farms are right next to each other." Over the course of a year, 95 percent of Mexico's farmed shrimp harvest—64 million pounds in 2000—makes its way to the United States. Most of the shrimp Americans consume come from abroad, and chances are excellent that they were farmed in Asia, Central or South America, or Mexico. We are also eating salmon raised on ranches that float in the seas off the coasts of Norway, Chile, Maine, and the Pacific Northwest. Slightly less than one-third of the seafood we consume is not wild at all, according to the U.S. Food and Drug Administration. It comes from aquaculture, a $52-billion-a-year global enterprise involving more than 220 species of fish and shellfish that is growing faster than any other food industry—so fast that fish farming is expected to exceed beef ranching within a decade. This blue revolution could help solve some big problems. It could provide fish for an ever-growing number of consumers and more food for the 1 billion chronically malnourished people worldwide who need protein. And it could do so while saving rapidly disappearing wild fish by relieving the pressure of commercial fishing. But Naylor is one of a group of scientists and environmentalists who are not convinced that aquaculture is beneficial. She contends that in many places, the practice is destroying land along coasts and causing water pollution. And instead of helping save wild fish, she argues, aquaculture may actually be hastening their demise. "To say that aquaculture shouldn't happen at all would be wrong," she says. "But right now aquaculture is a slash-and-burn activity, shrimp farming in particular."
View through an underwater camera used by technicians monitoring the release of food pellets at a salmon farm near Vancouver. About 50 percent of the protein in the pellets comes from fish meal and fish oil. "Farms are getting more efficient in controlling the amount of feed expended per fish," says aquaculture expert Rosamond Naylor. "But as the industry expands, it will require more wild fish to use as feed for farmed fish."
Seven months before her flight over the shrimp farms, Naylor visited a coastal portion of the Sonoran Desert the slow way, by car, boat, and foot. Traveling with her graduate student, Amy Luers, she wanted to get a sense of not only the scope of Mexico's aquaculture industry, which has roughly doubled in the past 10 years, but also its environmental and social effects. Naylor, a senior fellow at Stanford's Center for Environmental Science and Policy, studies how food grown intensively—particularly wheat and rice—affects national economies, laborers, and the environment. Now 44, she has spent most of her career conducting research in Asia but has also visited the state of Sonora at least 20 times since 1993 to study the green revolution and its environmental legacy and, increasingly, the effects of agriculture and aquaculture on coastal systems. She became interested in aquaculture a decade ago when she noticed that a growing number of the farmers she interviewed in Southeast Asia had begun to raise shrimp because it could be at least 10 times more lucrative than growing rice. An acquaintance of Naylor's once described her as a dynamo who looks disarmingly like a California surfer. She is petite with shoulder-length blond hair, blue eyes, a loud laugh, and a facility for bonding quickly with people. Her intensity puts people at ease instead of putting them off. She loves to be in the field, but on this trip she was not enjoying what she was hearing and seeing. One morning she and Luers visited a shrimp farm on the shore a few miles from the town of Navopatia. Shrimp farms can be simple affairs: a bulldozer digs into a field to create clusters of five-acre ponds on plots of land that range from 15 to 300 acres. A pipe at one end of the pond pulls clean ocean water in, and a pipe at another end spits water laden with shrimp feces, excess shrimp food, and, sometimes, antibiotics back into the ocean. This particular farm is situated on an estuary—where salt water and freshwater mix. An island nearby is thick with mangroves. Dolphins swim by, frigate birds, terns, cormorants, and pelicans fly by, and a great blue heron and an egret stagger into flight from a sandbar. "They've got an ideal site here," says Naylor, peering from the prow of a fishing boat. "There is no one around, and they are pumping out of the estuary." She then asks the two brothers piloting the boat what they think of the farm. "It is killing the fish," says Fortino Mendivil. His brother Eduardo agrees. That complaint is often heard along Mexico's Pacific coast. Environmental organizations and groups of fishermen here are beginning to rally against aquaculture, particularly in the state of Sinaloa, just south of Sonora, where aquaculture was first introduced in 1984. After the boat ride, Naylor and Luers interview Jorge Valenzuela, a farmer in the town of Moroncarit who is considering leasing his land to an aquaculture enterprise. They chat with him under the tangle of a cottonwood tree that holds as many shovels, bottles, and lengths of rope as it has branches. He says his three sons are now forced to fish far out at sea because the nearby estuary has been completely depleted. He, too, blames pollution from the shrimp farms. It is not entirely clear what is causing the decline of fish along the Sonoran coast, but aquaculture could be one of the culprits, along with overfishing. Here and elsewhere, intake pipes can pull in shrimp larvae, robbing fishermen of future catches. Excrement from shrimp and other cultivated species, including salmon, carp, tilapia, and catfish, can sully water adjacent to farms, driving away wild fish and other sea creatures. Feces rich in nitrogen trigger the growth of algae, which can clutter and then choke bodies of water—a process called eutrophication. The effluent can also release pests and diseases such as sea lice and viruses that thrive when shrimp or fish are packed together. These, in turn, can infect wild fish. A 1997 report by the U.S. National Marine Fisheries Service says two lethal viruses—infectious hypodermal and hematopoietic necrosis virus (IHHNV) and Taura syndrome virus—were first reported in aquaculture facilities and have subsequently been documented in wild shrimp populations in such places as Ecuador and Mexico. Although IHHNV may also be endemic to wild populations in some places, the evidence suggests that diseases can jump from farms into the wild.
(A) A typical shrimp farm in the southern Sonoran Desert of Mexico covers nearly 250 acres. (B) Four-month-old shrimp will be harvested within another two months. (C) "Disease can spread quickly between closely linked ponds," says Naylor, on a tour with locals who fish for shrimp the old-fashioned way.
Fish and shrimp wastewater may also contain antibiotics such as oxytetracycline and sulfadimethoxine, which are included in some fish-food formulations, says Stuart Levy, president of the nonprofit Alliance for the Prudent Use of Antibiotics. Levy and others worry that bacteria are developing resistance to these drugs; ultimately, people will suffer if they encounter resistant strains of Salmonella and Escherichia coli, both common causes of food poisoning, or Vibrio cholerae. In 1991 cases of drug-resistant cholera in Ecuador were first reported among shrimp-farm workers. Antibiotics can even be dangerous in their own right. In January the European Union banned the import of some aquacultural and meat products from China because they contained chloramphenicol, an antibiotic prohibited from use in food in both Europe and the United States because it has been linked to lethal blood disorders in humans. Environmentalists have warned about these dangers for years. And Levy says the aquaculture industry has made more dramatic reductions in the use of antibiotics than the agriculture industry. Some aqua farmers have even adopted pollution-prevention strategies such as polyculture, in which wastewater is used to grow something else, like hydroponic lettuce or seaweed for sushi. But such practices are the exception rather than the rule in the United States, says Naylor. And about 90 percent of aquaculture takes place in the developing world, where small farmers often don't have the capital to invest in environmental protection, and government regulations and enforcement are not powerful enough to strong-arm wealthier farmers. "Even if the industry's thinking may be moving ahead, the reality isn't there yet," Naylor says. "They are not treating their wastes, and there is disease." White spot syndrome virus, for example, has troubled the industry in recent years. Bob Rosenberry of Shrimp News International calculates that farmers lost about 660 million pounds in 2001 to white spot—more than 1 billion dollars' worth of shrimp. Naylor and others are concerned that the virus could find its way to wild shrimp, crabs, and crayfish. Criticism of the aquaculture industry took a new tack after Harold A. Mooney, an ecologist at Stanford who is on the board of Environmental Defense, introduced Naylor to Rebecca J. Goldburg, a biologist at the nonprofit organization. In 1997 Goldburg had written Murky Waters: Environmental Effects of Aquaculture in the United States, describing pollution produced by fish farming. The two women assembled a team of 10 people interested in or working on aquaculture, including Mooney, marine biologist Jane Lubchenco of Oregon State University, and anthropologist Jason Clay, a senior fellow with the World Wildlife Fund. With Naylor and Goldburg at the helm, they wrote two papers. One appeared in the journal Science in 1998, the other in the journal Nature in 2000. The Nature report, featured on the cover with the tag line "The Downside of Fish Farming," included familiar complaints about aquaculture: It causes pollution, and it leads to the destruction of coastal ecosystems because farmers clear out plants with bulldozers and alter the way water flows when they dump the displaced dirt and sand. But it also raised a criticism that had been less prominently aired: Some forms of aquaculture, in particular, the farming of carnivorous species, can hurt wild fish. The authors contend that certain farmed species escape their ponds or pens, consuming the resources of wild fish and, if inbreeding occurs, endangering the genetic strength of wild species. In the Pacific Northwest, where coho, chinook, and sockeye salmon are listed under the U.S. Endangered Species Act, the concern is growing. Biologist John Volpe of the University of Alberta estimated that in 1999, for example, between 55,400 and 110,800 Atlantic salmon escaped from Canadian fish ranches (which are made up of a series of 10 to 30 underwater 40- or 50-square-foot cages, each holding 20,000 salmon and anchored off the coast). These Atlantic salmon have been found in 17 Pacific Northwest rivers so far, which means they are eating and breeding in the habitat of Pacific salmon and endangered steelhead trout. Biologists fear that the interlopers may ultimately push out the locals. In addition to becoming invasive species themselves, cultured creatures sometimes carry other species or diseases with them. Sea lice, for example, which eat the flesh of the fish and thrive in the fin-to-fin conditions of salmon ranches, have also affected wild salmon near places with salmon aquaculture. Such an outbreak was recently reported by Alexandra Morton, a biologist living in British Columbia. Salmon anemia, which is sometimes carried by sea lice, forced farmers to kill 1.5 million salmon last year in Maine. Despite that effort, the National Oceanic and Atmospheric Administration reported recently that the disease has already been observed in wild Atlantic salmon. Another threat to wild fish, say Naylor and her colleagues, is even more direct: Farmed fish eat wild fish. Carnivorous aquaculture species such as salmon, shrimp, eel, flounder, halibut, tuna, and sea bass are fed fish meal and fish oil—essentially ground or pressed anchovies, sardines, capelin, blue whiting, mackerel, Atlantic herring, and other small bony fish. Each year roughly 66 billion pounds of these fish are used as feed, a growing percentage of which is going to aquaculture: 10 percent in 1988, 35 percent in 1997. For some farmed marine species, as many as five pounds of wild fish are needed for one pound of growth. In Naylor's view, as aquaculture continues to expand—about 10 percent per year in the 1990s—farmed fish could lead to the depletion in some regions of the small wild fish upon which much of the marine food chain depends. "This is environmental advocacy being cloaked in science, and I think that is a very dangerous thing," responds John Hargreaves, an associate professor in the Department of Wildlife and Fisheries at Mississippi State University. "Some of the issues that have been raised by the environmentalists are legitimate. You can find examples of bad behavior everywhere. But to cite those examples as generalities is not responsible." Likewise, James Tidwell, coordinator of aquaculture programs at Kentucky State University and past president of the World Aquaculture Society, is angered by the contention that aquaculture damages wild fisheries. "I am not without sin, but I am not real good at paying for ones I did not commit," he says. "Most of the fisheries were in brutal condition before aquaculture was even on the scene." In addition, Tidwell and others argue that fish-meal production has remained constant for many years, despite the growth of aquaculture. "We are at a sustainable yield now," Tidwell says. "If aquaculture doesn't use it, someone else will." And he notes that there is no evidence that the use of fish meal for aquaculture has led to the depletion of wild fish either. Aquaculture critics respond that it's only a matter of time before the loss of wild fish is more readily apparent. "The evidence is there about how much fish meal is being used, and it is logical that if consumption goes up, there will be more and more effort to fish those stocks," says Clay at the World Wildlife Fund. Naylor says that if the Nature article encouraged aquaculture owners to think more about the effect on the ecosystem and the potential problem of supplying fish meal, it did its job: "I didn't mind the controversy, because my opinion was that they have to stand up to what they are saying, and if this is the way to get them to prove they are right, that is fine."
Each of 10 salmon cages at a farm near Vancouver is 100-feet square, 80-feet deep, and holds 100,000 baby fish. The distribution of food pellets, from spinning cones suspended above red floats, is computer-controlled.
A red tide extending more than 46 square miles bloomed in June near 27 fish farms off the coast of British Columbia. Biologist Alexandra Morton links the explosion of algae to farms "introducing so much organic waste into the water."
Morton holds a lice-infested pink salmon fry. "Salmon lice on juveniles were never seen until the farms came here," she says. "Big fish survive lice, but the little guys are doomed because they don't have as much body mass."
Brown's Bay Packing on Vancouver Island is the end of the production line for many salmon raised on nearby fish farms. Several 12- to 16-pound salmon, already gutted, filleted, and packed in ice, are ready for shipping.
High above the Sonoran Desert recently, Naylor mused about similarities between the green revolution and the blue revolution. "We flew over the whole area of the green revolution, and we noticed that all the old rivers and streambeds were dried up because irrigation was directing the water," she says. "And when we got down to the coast, the blue revolution was doing the same. The ecosystem is really engineered to the max." The term green revolution comes from work by Norman Borlaug in the 1950s to breed a dwarf form of wheat that is bountiful because it is short. It can produce more grain because it grows low to the ground and it doesn't tip over with the weight of the kernels. That innovation ushered in an era of selective crop breeding, irrigation, fertilizer, and pesticides. The world had never seen such bounty, but it didn't anticipate the environmental costs. The green revolution also led to waterways deadened by eutrophication, ecosystems altered because irrigation had drained rivers and streams, and various health problems due to increased use of pesticides. The blue revolution promises bountiful harvests as well. It already brings food to many people, both as protein and as desperately needed income. "When you talk to a farmer who has five kids and is trying to feed them now, the urgency of that dominates everything," Naylor says. As with the green revolution, however, the challenge facing the nascent blue revolution is to take into account the larger ecosystem. Naylor and her colleagues argue that wider use of polyculture systems could help make aquaculture more environmentally friendly. Shellfish aquaculture can help cleanse entire waterways, says Sandra Shumway, a marine biologist at the University of Connecticut, because clams, scallops, and mussels filter water for food: A three-inch oyster, for example, can filter about six gallons a day. Another key to making the blue revolution more environmentally acceptable, says Naylor, is to teach new methods to poor farmers. She says organizations like agricultural cooperatives should be developed for aquaculture. Then farmers could get free basic training about how to stock a pond, prevent disease, and treat effluents. "Many of them are trying to do a good job," Naylor says. "They are not trying to destroy the environment. They are just trying to make a living and contribute to the market. But they are not going to take on the stewardship issue themselves." Educating farmers could also help reduce antibiotic use. "It is safe to say that most enlightened producers wouldn't use antibiotics at all, because they are dealing with mostly viral diseases," Clay says. "But a lot of producers don't necessarily understand that." In the past 10 years, antibiotic use has dropped between 70 and 90 percent. But a February report by the U.S. Institute for Agriculture and Trade Policy estimates that between 204,000 and 433,000 pounds are still used every year in the United States alone. That's a fraction of what is fed to livestock, researchers say, but still plenty to allow mobile waterborne germs to learn to mutate against the effects of antibiotics. To eliminate the problem, Clay recommends that governments prohibit the inclusion of antibiotics in any manufactured feed: "No one manufactures their own feed, so that is a place you could have some control over the system." Or, he says, the 200 to 400 buyers who purchase all the shrimp for the U.S. market could be pressured not to buy any that have been treated with antibiotics. Clay and Naylor think aquacultural products should be labeled so consumers can exert influence over how and where their food is produced. Each shipment of shrimp that enters this country—mostly through California—already has a bar code, says Clay. "In many countries, it can tell you which producer and which pond. We have the means available right now to track a product back to a source if there is a problem." Consumers might also be encouraged to eat carp, catfish, tilapia, and other herbivores. That would bring down demand for farm-bred carnivorous fish that deplete the population of wild fish. And wild fish could be further protected if industry experts continue to refine fish food, Naylor says, "One of the positive things on the salmon side has been the focus on the feed issue and trying to improve it." The most recent data on salmon shows that 2.44 pounds of wild fish were needed in 2000 as food to produce one pound of salmon growth, compared with 3.16 pounds in 1997. Naylor is convinced that these improvements could help the blue revolution succeed in areas where the green revolution failed. Given the diversity and global character of the industry, she has set her sights high. But consider this: She has seen a desert turn first green and now blue, and she has seen crustaceans swimming amid cacti. In the light of such wonders, anything seems possible.
Salmon raised in a coastal farm are harvested after spending up to 18 months in net pens suspended from steel walkways. Industry officials say that the survival rate is 90 to 95 percent, compared with less than 10 percent for wild salmon. Morton argues that the practice of anchoring farms on wild salmon migration routes puts wild fish at risk. "Sick wild fish are picked off by predators," she says. "Sick farmed fish are coddled but pass on pathogens to wild fish on the migration routes."
Goldburg, Rebecca J., et al. "Marine Aquaculture in the United States: Environmental Impacts and Policy Options." Pew Oceans Commission, Arlington, Va., 2001. Available online at www.pewoceans.org/oceanfacts/2002/01/11/fact_22988.asp.