A new study of dozens of wild fish species commonly consumed in the Peruvian Amazon says that if the persistent loss of fish species diversity continues, people there could suffer from severe nutritional deficiencies. In addition, the increasing use of aquaculture and other substitutes may not be able to compensate for this. The research is having an impact far beyond the Amazon as the diversity and abundance of wild-harvested food declines in rivers and lakes around the world as well as on land. Around 2 billion people worldwide are dependent on uncultivated food; Inland fishing alone employs about 60 million people and is the main source of protein for about 200 million. The study appears in the Journal this week Scientific advances.

The authors examined the vast, rural Loreto department of the Peruvian Amazon, where most of the 800,000 residents eat fish at least once a day, averaging about 52 kilograms per year. This is their main source not only of protein, but also of fatty acids and essential trace elements such as iron, zinc and calcium. Unfortunately, it’s not enough; a quarter of all children are malnourished or stunted, and more than a fifth of women of childbearing age are iron deficient.

Threats to the Amazon fishery, long a pillar of both indigenous peoples and modern development, are legion: new hydroelectric dams that imprison large migratory fish (some stretch thousands of kilometers from the Andes headwaters to the Atlantic estuary and back) ; Soil erosion in rivers from deforestation; toxic runoff from gold mines; and overfishing by the fishermen themselves, who struggle to feed the rapidly growing populations. In Loreto the catches are stagnating; some large migratory species are already on the retreat, others may be on the way. It is different too; According to the World Wildlife Fund, a third of the world’s freshwater fish species are critically endangered and 80 are already known to be extinct.

Different species of animals and plants contain different ratios of nutrients, so biodiversity is key to adequate human nutrition, the researchers say. “If the fish wears off, the quality of the diet will degrade,” said study’s lead co-author Shahid Naeem, director of the Earth Institute Center for Environmental Sustainability at Columbia University. “Things are definitely going back now and they could be on the way to crashing.”

To study the region’s fish, the study’s lead author, then Columbia PhD. Student Sebastian Heilpern, made numerous shopping trips to the bustling Belén retail market in the provincial capital of Iquitos. He also visited the city’s Amazon docks, where wholesale starts at 3:30 a.m. He and another student bought several specimens of as many different species as they could find and ended up with 56 of the region’s 60 or so most important foods. These included humble scaled fish known locally as Ractacara and Yulilla; saucer-shaped palometa (related to piranha); and giant catfish that span six feet or more. (The researchers have been satisfied with parts of the largest.)

The fish were flown on ice to a government laboratory in Lima, where each species was analyzed for protein, fatty acids and trace elements. The researchers then plotted the nutritional value of each species against their likelihood of surviving various types of persistent environmental degradation. From this, they developed several scenarios of how future human diets would affect if different species were left out of the mix.

Overall, the biomass of the caught fish has remained stable in recent years. However, large migratory species, most vulnerable to human activity, make up a declining proportion and as they disappear they are replaced by smaller local species. Most fish contain roughly the same amount of protein, so this has not affected the protein supply. And the researchers found that many smaller fish actually have higher levels of omega-3 fatty acids, so ingesting them can actually increase that supply. On the other hand, as the species mix tends to be more towards smaller fish, iron and zinc supplies are already declining and will continue to decline, they say.

“As with any other complex system, you can see a compromise here,” says Heilpern. “Some things rise while others fall. But it only takes up to a point. ”Which species will fill in the gaps when others decline is difficult to predict – but researchers believe that the overall nutritional value of catches will decrease by the point where 40 of the 60 food species will be become scarce or become extinct. “You have a tipping point where the remaining species can be really lousy,” Heilpern said.

One possible solution: In many places around the world where wild foods like fish and bushmeat (like monkeys and lizards) are declining, people are increasingly turning to chicken farming and aquaculture – a trend promoted by the World Bank and other great powers Organizations. This is increasingly the case in Loreto. In a separate study published in March, Heilpern, Naeem and their colleagues show that this, too, undermines human nutrition.

The researchers observed that from 2010 to 2016, chicken production in the region increased by about three-quarters, and aquaculture almost doubled. However, when analyzing the nutritional values ​​of the farm animals, they found that they tend to be poorer in nutrition than a diverse mix of wild fish. In particular, the switch to chicken and aquaculture will likely worsen the already serious iron deficiency in the region and reduce the supply of essential fatty acids, it is said. “Since no single species can provide all of the essential nutrients, biodiversity is required to maintain a nutrient-adequate diet,” they write.

In addition, poultry farming and aquaculture pollute the environment far more than fishing. In addition to promoting the clearing of forests to produce feed for the animals, animal husbandry produces more greenhouse gases and brings fertilizers and other pollutants into the nearby waters, says Heilpern.

“Inland fish are fundamental to nutrition in many low-income and food-scarce countries, and of course in landlocked countries,” said John Valbo Jørgensen, a Rome-based inland fisheries expert with the United Nations Food and Agriculture Organization. “Many significant inland fisheries, including that in Peru, take place in remote areas with poor infrastructure and limited resources. It will not be possible to replace these fisheries with livestock, including fish. “

In collaboration with the Wildlife Conservation Society, Heilpern is now creating an illustrated guide to the area’s fish, including their nutritional values, to help fishermen and consumers better understand their value.

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The other authors of the new study are Ruth deFries and Maria Uriarte of the Earth Institute; and Kathryn Fiorella, Alexander Flecker, and Suresh Sethi from Cornell University.

Scientific contacts:

Sebastian Heilpern [email protected]

Shahid Naeem [email protected]

Ruth deFries [email protected]

More information: Kevin Krajick, Senior Editor, Science News, The Earth Institute [email protected] 212-854-9729

Columbia University’s Earth Institute mobilizes science, education, and public policy to achieve a sustainable earth. http: // www.Earth.Columbia.edu .

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