Falling fish catches could mean malnutrition in the developing world

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Jun 15, 2016

The world won’t be able to fish its way to feeding 10 billion people by midcentury, but a shift in management practices could save hundreds of millions of fish-dependent poor from malnutrition, according to a new analysis by members of the Fisheries and Food Security science team supported by the National Socio-Environmental Synthesis Center (SESYNC) at the University of Maryland. The researchers utilized new databases on global fish catch and on human dietary nutrition and found that the vulnerability of poor, fish dependent populations in the tropics has been underestimated and that these are the very places whose fish resources are under the most intense pressure. The report was published June 16 as a commentary in the journal Nature.

“SESYNC is a leader in providing funding for critical efforts to address emerging problems--such as issues around falling fish catches and malnutrition in the developing world--through new interdisciplinary partnerships to improve understanding,” said Dr. Margaret Palmer, executive director of SESYNC. “The scholarship that Chris Golden and his team have clearly highlighted in their Nature commentary is a powerful reminder that interdisciplinary synthesis research has the potential to uniquely inform decisions and improve the design of public policies.”

At its heart, the problem is a simple one of supply and demand: global fish catches peaked in 1996, while the Earth’s human population is expected to rise through 2050, from the current 7.3 billion to between 9 billion and 10 billion.

But that straightforward dynamic oversimplifies a problem also affected by natural processes, economic pressures, international regulations, and human health needs.

Lead author Christopher Golden, research scientist at the Harvard T.H. Chan School of Public Health and associate director of the Planetary Health Alliance, said that it isimportant to include human nutrition, along with biodiversity preservation and economic considerations, in determining how fisheries are managed.

The work estimates that, in the coming decades, 11 percent of global population – 845 million people -- is vulnerable to micronutrient deficiencies due to its reliance on seafood, a figure that climbs to 19 percent, or 1.39 billion people, if nutrients only found in animal sources, such as vitamin B12 and DHAomega-3 fatty acids, are included.

The analysis of two new databases, one from Sea Around Us at the University of British Columbia and the other from a team led by Samuel Myers at the Harvard T.H. Chan School of Public Health, says that those most likely to suffer the impact of fisheries’ decline are the global poor, particularly those for whom fish make up a significant part of their diet.

“We’re missing an enormous piece of this picture, because many of the consequences of the way we manage resources and conserve natural systems will have very strong and powerful downstream effects on human health,” Golden said. “It’s not just a biodiversity issue, it’s not just an economics issue. We need to be really thinking through this third dimension, human health and well-being.”

While fish are recognized as an important source of protein, they also provide often overlooked micronutrients—like vitamin B12, iron and zinc, Golden said. According to the report, micronutrient deficiencies can affect maternal mortality, child mortality, cause cognitive defects, and impact immune function. Some 45 percent of mortality in children under age five is attributable to undernutrition.

The report says that the vulnerability of these poor, fish dependent populations in the tropics has been underestimated and that these are the very places whose fish resources are under the most intense pressure.

The problems facing subsistence fishing populations are not solely due to overfishing, which has been successfully addressed in some locations through sound management. In addition, destructive fishing practices and coastal pollution are degrading the aquatic environment, while climate change is also expected to have an effect. Warmer water and acidification bleaches coral reefs while rising temperatures force tropical species poleward. Climate change’s effects could reduce catch by 6 percent globally and by as much as 30 percent in certain tropical regions. Warming tropical seas will hold less oxygen and cause fish to get smaller, cutting overall biomass by about 20 percent by 2050.

Golden said those in industrialized nations can compensate for the nutritional gap left by a decline of fish in the diet. They can afford to buy replacement foods, supplements, and vitamins, while those in developing nations often have few alternatives.

Even among developing nations, however, there is much variation in the threats to local fish supplies. A large island nation like Madagascar, where Golden has worked on the interface between human health and the environment for 17 years, suffers most from unsustainable fishing practices and foreign fleets in its waters – issues that could be addressed with better management. Small island developing states, like Kiribati, Maldives, Palau, and Vanuatu, however, may have more intractable problems. Climate change will likely push local fish species toward the poles, while rising seas may flood low-lying areas where aquaculture is practiced. Many of those in their populations, meanwhile, are too poor to afford high quality replacement foods or to buy supplements to replace nutrients once received from dietary fish.

That means populations too poor to buy market substitutes, as in Madagascar, will likely fall back on less-nutrient rich foods, like rice and tubers. Those in wealthier nations, like Philippines, Brazil, Mexico, and Indonesia, meanwhile, may buy cheap processed foods to replace fish, which would increase the risk of metabolic diseases rather than undernutrition, Golden said.

“Wealthy nations are somewhat immune to these environmental effects. They can create systems of food imports, intensive agricultural food production, fortified foods, and supplements that buffer them from the potential pitfalls or consequences, whereas it is poorer populations dependent on the direct pathway from the environment to their own wellbeing that are most at risk,” Golden said. “There’s almost a reverse Robin Hood system where the wealthier nations are now going into biodiversity rich areas, with robust fish populations, and using foreign fleets to capture resources – both legally and illegally - and bring them back to wealthier populations that don’t need them.”

Aquaculture is seen by some as an answer to the problem, but Golden said that isn’t the case, at least as currently practiced. While global aquaculture production has exploded, outstripping wild catch destined for human consumption for the first time in 2014, much of the production is intended for tables in the developed world or for developing nations’ urban elite. In addition, he said, aquaculture is not entirely divorced from wild fisheries, as the fish meal fed farmed fish comes from wild caught stock.

While it’s unlikely that wild harvests will provide the same nutrition for midcentury’s significantly larger human population, better management can improve catches by as much as 10 percent, Golden said, and, if those practices have human nutrition in mind, hundreds of millions of cases of malnutrition can be avoided.

“The hopeful thing is that policy and management has been shown to rebound fisheries on the scale of a decade,” Golden said. “So it’s a really important time to be sounding this alarm so nutrition-sensitive policies can be implemented.”

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