Giant new snake species identified in the Amazon

A team of scientists on location with a film crew in the remote Amazon has uncovered a previously undocumented species of giant anaconda.

Professor Bryan Fry from The University of Queensland led a team which captured and studied several specimens of the newly named northern green anaconda (Eunectes akayima), located in the Bameno region of Baihuaeri Waorani Territory in the Ecuadorian Amazon.

"Our team received a rare invitation from the Waorani people to explore the region and collect samples from a population of anacondas, rumoured to be the largest in existence," Professor Fry said.

"The indigenous hunters took us into the jungle on a 10-day expedition to search for these snakes, which they consider sacred.

"We paddled canoes down the river system and were lucky enough to find several anacondas lurking in the shallows, lying in wait for prey.

"The size of these magnificent creatures was incredible -- one female anaconda we encountered measured an astounding 6.3 metres long.

"There are anecdotal reports from the Waorani people of other anacondas in the area measuring more than 7.5 metres long and weighing around 500 kilograms."

Professor Fry said the northern green anaconda species diverged from the southern green anaconda almost 10 million years ago, and they differ genetically by 5.5 per cent.

"It's quite significant -- to put it in perspective, humans differ from chimpanzees by only about 2 per cent," he said.

"This discovery is the highlight of my career."

The new anaconda species was found while filming with National Geographic for their upcoming Disney+ series Pole to Pole with Will Smith, on which Professor Fry, a National Geographic Explorer, was the expedition's scientific leader.

"Our journey into the heart of the Amazon, facilitated by the invitation of Waorani Chief Penti Baihua, was a true cross-cultural endeavour," he said.

"The importance of our Waorani collaborators is recognised with them being co-authors on the paper."

The scientists also set out to compare the genetics of the green anaconda with specimens collected elsewhere by world-leading anaconda expert Dr Jesus Rivas from New Mexico Highlands University, and use them as an indicator species for ecosystem health.

Professor Fry said the Amazon continues to face alarming ecological threats.

"Deforestation of the Amazon basin from agricultural expansion has resulted in an estimated 20-31 per cent habitat loss, which may impact up to 40 per cent of its forests by 2050," he said.

"Another increasing problem is habitat degradation from land fragmentation, led by industrialised agriculture and heavy metal pollution associated with spills from oil extraction activities.

"Forest fires, drought and climate change are also notable threats.

"These rare anacondas, and the other species that share this remote ecosystem, face significant challenges."

Professor Fry said his next research project would focus on heavy metal pollution in the Amazon.

"It's not only these gigantic snakes that are facing environmental threats, but almost all living things in the region," he said.

"The discovery of a new species of anaconda is exciting, but it is critical to highlight the urgent need to further research these threatened species and ecosystems.

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Naturally regrowing forests are helping to protect the remaining old forests in the Amazon

The climate crisis and UN Decade on Ecosystem Restoration have generated great interest in the value of secondary forests. These are forests that have regrown naturally on land abandoned from agriculture.

Collaborative research between Lancaster University, Bangor University and the University of British Columbia has produced new evidence of just how important they are in counteracting the effects of forest fragmentation across the Amazon basin. This has just been published in a paper in the journal Environmental Research Letters. It is an output of the PhD research of Charlotte Smith, in the Envision Doctoral Training Partnership, in which Bangor University is a partner.

Co-author of the paper, John Healey, Professor of Forest Sciences at Bangor University, described how it shows "that secondary forests cover just 190,000 km2 of the Amazon but connect more than 2 million isolated fragments of old-growth forest, prominent amongst the world's most important habitats for biodiversity conservation. The secondary forests are helping maintain connectivity for patches of old-growth forest that are too small to support long-term viable populations of rare species."

Charlotte Smith reported "secondary forests are buffering as much as 41% of old-growth forest edges, potentially shielding them from negative edge effects such as hotter temperatures and wind. Proximity to old-growth forests can also help the rate of biodiversity and biomass recovery in secondary forests. It is positive that 94% of secondary forests were connected to old-growth forest. However, may old-growth forest remnants are small and degraded patches, so only 57% of secondary forest was connected to an area of extensive, structurally-intact old-growth."

Professor Healey pointed out the importance of this research, "It provides powerful new evidence of the importance of managing forests at the landscape scale. Promoting forest restoration through secondary forests located next to old-growth forest remnants can play a vital role in both conserving biodiversity in these remnants and the rate of biodiversity recovery in the secondary forests themselves."

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Climate change likely to uproot more Amazon trees

Tropical forests are crucial for sucking up carbon dioxide from the atmosphere. But they're also subject to intense storms that can cause "windthrow" -- the uprooting or breaking of trees. These downed trees decompose, potentially turning a forest from a carbon sink into a carbon source.

A new study finds that more extreme thunderstorms from climate change will likely cause a greater number of large windthrow events in the Amazon rainforest. This is one of the few ways that researchers have developed a link between storm conditions in the atmosphere and forest mortality on land, helping fill a major gap in models.

"Building this link between atmospheric dynamics and damage at the surface is very important across the board," said Jeff Chambers, a senior faculty scientist at the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab), and director of the Next Generation Ecosystem Experiments (NGEE)-Tropics project, which performed the research. "It's not just for the tropics. It's high-latitude, low-latitude, temperate-latitude, here in the U.S."

Researchers found that the Amazon will likely experience 43% more large blowdown events (of 25,000 square meters or more) by the end of the century. The area of the Amazon likely to see extreme storms that trigger large windthrows will also increase by about 50%. The study was published in the journal Nature Communications on Jan. 6.

"We want to know what these extreme storms and windthrows mean in terms of the carbon budget and carbon dynamics, and for carbon sinks in the forests," Chambers said. While downed trees slowly release carbon as they decompose, the open forest becomes host to new plants that pull carbon dioxide from the air. "It's a complicated system, and there are still a lot of pieces of the puzzle that we're working on. In order to answer the question more quantitatively, we need to build out the land-atmosphere links in Earth system models."

To find the link between air and land, researchers compared a map of more than 1,000 large windthrows with atmospheric data. They found that a measurement known as CAPE, the "convective available potential energy," was a good predictor of major blowdowns. CAPE measures the amount of energy available to move parcels of air vertically, and a high value of CAPE often leads to thunderstorms. More extreme storms can come with intense vertical winds, heavy rains or hail, and lightning, which interact with trees from the canopy down to the soil.

"Storms account for over half of the forest mortality in the Amazon," said Yanlei Feng, first author on the paper. "Climate change has a lot of impact on Amazon forests, but so far, a large fraction of the research focus has been on drought and fire. We hope our research brings more attention to extreme storms and improves our models to work under a changing environment from climate change."

While this study looked at a future with high carbon emissions (a scenario known as SSP-585), scientists could use projected CAPE data to explore windthrow impacts in different emissions scenarios. Researchers are now working to integrate the new forest-storm relationship into Earth system models. Better models will help scientists explore how forests will respond to a warmer future -- and whether they can continue to siphon carbon out of the atmosphere or will instead become a contributor.

"This was a very impactful climate change study for me," said Feng, who completed the research as a graduate student researcher in the NGEE-Tropics project at Berkeley Lab. She now studies carbon capture and storage at the Carnegie Institution for Science at Stanford University. "I'm worried about the projected increase in forest disturbances in our study and I hope I can help limit climate change. So now I'm working on climate change solutions."

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Companies' 'deforestation-free' supply chain pledges have barely impacted forest clearance in the Amazon, researchers say

More companies must make and implement zero-deforestation supply chain commitments in order to significantly reduce deforestation and protect diverse ecosystems, say researchers.

Corporate pledges not to buy soybeans produced on land deforested after 2006 have reduced tree clearance in the Brazilian Amazon by just 1.6% between 2006 and 2015.

This equates to a protected area of 2,300 km2 in the Amazon rainforest: barely the size of Oxfordshire in the UK.

The findings, made by tracing traders' soy supplies back to their source, are published today in the journal Environmental Research Letters. The work involved a team from the University of Cambridge, Boston University, ETH Zurich and New York University.

The researchers also discovered that in the Cerrado, Brazil's tropical savannah, zero-deforestation commitments have not been adopted effectively -- leaving over 50% of soy-suitable forests and their biodiversity without protection.

Brazil has the largest remaining tropical forests on the planet, but these are being rapidly cleared to rear cattle and grow crops including soybean. Demand for soy is surging around the world, and an estimated 4,800 km2 of rainforest is cleared each year to grow soybeans.

The majority of soy is consumed indirectly by humans: soybean is widely used as feed for factory-farmed chickens, pigs, fish and cattle. It also accounts for around 27% of global vegetable oil production, and as a complete protein source it often forms a key part of vegetarian and vegan diets.

By 2021, at least 94 companies had adopted zero-deforestation commitments -- pledging to eliminate deforestation from their supply chains. But the study revealed that many of these commitments are not put into practice.

And the researchers say that adoption of zero-deforestation commitments is lagging among small and medium sized food companies.

"Zero-deforestation pledges are a great first step, but they need to be implemented to have an effect on forests -- and right now it's mainly the bigger companies that have the resources to do this," said Professor Rachael Garrett, Moran Professor of Conservation and Development at the University of Cambridge Conservation Research Institute, a joint senior author of the report.

She added: "If soybean traders actually implemented their global commitments for zero-deforestation production, current levels of forest clearance in Brazil could be reduced by around 40 percent."

Deforestation is the second largest contributor to global greenhouse gas emissions after fossil fuel use. It also causes the loss of diverse animal and plant life, threatens the livelihoods of indigenous groups, and increases inequality and conflict.

The researchers say that the supply chains of other food products including cattle, oil palm and cocoa supply chains are more complex than soy, making them even more difficult to monitor.

"If supply chain policies intend to contribute to the task of tackling deforestation in Brazil, it's crucial to expand zero-deforestation supply chain policies beyond soy," said Garrett, who is also Professor of Environmental Policy at ETH Zurich.

A 'soy moratorium' was the first voluntary zero-deforestation commitment in the tropics -- by signing it, companies agreed not to buy soybeans produced on land deforested after 2006. But while the commitment was implemented in the Brazilian Amazon, most Brazilian soy is produced in the Cerrado -- which is rich in biodiversity.

The researchers say their findings suggest private sector efforts are not enough to halt deforestation: supportive political leadership is also vital to conservation efforts.

"Supply chain governance should not be a substitute for state-led forest policies, which are critical to enable zero deforestation monitoring and enforcement, have better potential to cover different crops, land users, and regions," said Garrett.

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Archaeologists reveal pre-Hispanic cities in Bolivia with laser technology

More than 20 years ago, Dr. Heiko Prümers from the German Archaeological Institute and Prof. Dr. Carla Jaimes Betancourt from the University of Bonn, at that time a student in La Paz, began archaeological excavations on two "mounds" near the village of Casarabe in Bolivia. The Mojos Plains is a southwestern fringe of the Amazon region. Even though the savannah plain, which flooded several months a year during rainy season, does not encourage permanent settlement, there are still many visible traces of the time before Spanish colonization at the beginning of the 16th century. Next to the "mounds," these traces include mainly causeways and canals that often lead for kilometers in a dead straight line across the savannahs.

"This indicated a relatively dense settlement in pre-Hispanic times. Our goal was to conduct basic research and trace the settlements and life there," says Heiko Prümers. In earlier studies, the researchers already found that the Casarabe culture -- named after the nearby village -- dates to the period between 500 and 1400 AD and, according to current knowledge, extended over a region of around 16,000 square kilometers. The "mounds" turned out to be eroded pyramid stumps and platform buildings.

Initial conventional surveys revealed a terraced core area, a ditch-wall enclosing the site, and canals. In addition, it became apparent that some of these pre-Hispanic settlements were enormous in size. "However, the dense vegetation under which these settlements were located prevented us from seeing the structural details of the monumental mounds and their surroundings," says Carla Jaimes Betancourt from the Department for the Anthropology of the Americas at the University of Bonn.

LIDAR technology used in the Amazon for the first time

To find out more, the researchers used the airborne laser technology LIDAR (Light Detection and Ranging) for the first time in the Amazon region. This involves surveying the terrain with a laser scanner attached to a helicopter, small aircraft or drone that transmits around 1.5 million laser pulses per second. In a subsequent evaluation step, the vegetation is digitally removed creating a digital model of the earth's surface, which can also be displayed as a 3D image. "The first results were excellent and showed how effective the technology was even in dense rainforest. From that moment on, the desire arose to map the large settlements of the Casarabe culture using LIDAR technology," says study leader Dr. Heiko Prümers.

For the current study, in 2019 the team together with Prof. Dr. José Iriarte and Mark Robinson from the University of Exeter, mapped a total of 200 square kilometers of the Casarabe cultural area. The evaluation done by the company ArcTron3 held a surprise. What came to light were two remarkably large sites of 147 hectares and 315 hectares in a dense four-tiered settlement system. "With a north-south extension of 1.5 kilometers and an east-west extension of about one kilometer, the largest site found so far is as large as Bonn was in the 17th century," says co-author Prof. Dr. Carla Jaimes Betancourt.

It is not yet possible to estimate how many people lived there. "However, the layout of the settlement itself tells us that planners and many active hands were at work here," says Heiko Prümers. Modifications made to the settlement, for example the expansion of the rampart-ditch system, also speak to a reasonable increase in population. "For the first time, we can refer to pre-Hispanic urbanism in the Amazon and show the map of the Cotoca site, the largest settlement of the Casarabe culture known to us so far," Prümers emphasizes. In other parts of the world similar agrarian cities with low population densities had already been found.

LIDAR shows anthropogenically altered landscape

LIDAR mapping reveals the architecture of the settlement's large squares. Stepped platforms topped by U-shaped structures, rectangular platform mounds, and conical pyramids (up to 22 meters high). Causeway-like paths and canals connect the individual settlements and indicate a tight social fabric. At least one other settlement can be found within five kilometers of each of the settlements known today. "So the entire region was densely settled, a pattern that overturns all previous ideas," says Carla James Betancourt, who is a member of the Transdisciplinary Research Area "Present Pasts" at the University of Bonn.

The researchers emphasize that for all the euphoria about the site mappings and the possibilities they offer for reinterpreting the settlements in their geographic setting, the real archaeological work is just beginning. The goal for the future, they say, is to understand how these large regional centers functioned.

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Amazon deforestation threatens newly discovered fish species in Brazil

Smithsonian's National Museum of Natural History researcher Murilo Pastana and his colleagues have discovered and described two new species of Amazonian fish -- one with striking red-orange fins and the other so small it is technically considered a miniature fish species -- in a paper published today, May 16, in the Zoological Journal of the Linnean Society.

Both species inhabit waters located at the bleeding edge of human encroachment into the Amazon rainforest roughly 25 miles north of the Brazilian city of Apuí. Pastana and his co-authors, Willian Ohara with the Federal University of Rondônia and Priscila Camelier with the Federal University of Bahia, said that ongoing deforestation in the region places these roughly inch-long fish, part of a group known colloquially as the South American darters, in imminent danger of extinction. In particular, the more colorful of the two species, Poecilocharax callipterus, is at risk because its known range is limited to a single stream comprising roughly 1.5 square miles of habitat.

"It was exciting to find new species," Pastana said. "But in the field, we saw the forest on fire, logging trucks carrying out huge trees, and cleared patches turned into cattle pasture. This made us feel a lot of urgency to document these species and publish this paper as quickly as possible."

As a Brazilian-born scientist, Pastana is passionate about preserving the country's biological heritage, and his hope is that naming and describing these species might motivate the Brazilian government to protect and conserve these newly discovered, endangered fishes.

The small subfamily to which these previously unknown fish species belong is also highly desirable in the aquarium hobbyist market. Pastana, whose work is supported by the Smithsonian's Sara E. and Bruce B. Collette Postdoctoral Fellowship in Systematic Ichthyology, said that the exotic aquarium fish trade could pose yet another threat to these two new species even as scientists are first formally identifying them and learning of their existence.

The expeditions that uncovered these new freshwater species took place between 2015 and 2016. Pastana said the broad goal of these forays into the Brazilian Amazon was to search out the still unknown biological treasures of the many waterways in the Madeira River Basin, the richest river basin in the world in terms of fish biodiversity according to a 2019 estimate.

"We went to sample places that have never been visited by scientists," Pastana said. "This area is really important because this is one of the frontiers where deforestation is moving north -- the border between new cities and native forest."

The Apuí region where these scientific surveys took place sits at number two on a recent list of Brazilian municipalities with the highest deforestation rates. Ironically, the same roads that facilitate the region's accelerating loss of habitat also facilitated access to formerly unreachable streams, ponds and tributaries for Pastana and his colleagues.

So, in 2015 and 2016 Pastana and others camped along a road called AM-174 and collected fish using nets, traps and other methods. All the specimens were photographed, cataloged and preserved for further study back at the Museum of Zoology, University of São Paulo.

One of these specimens has vivid red-orange fins and a distinctive dark spot just in front of its tail. This fish stood out immediately as a new species, Pastana said. The fish, which has now been named P. callipterus, inhabits the margins of what scientists call a black water stream, so named because its waters are stained the color of coffee by tannins leached from fallen leaves. Males of the species have even more intense coloration and sport dorsal fins that can exceed half their body length, which averages just over an inch. Despite targeted efforts to seek out this species in the surrounding area on the 2016 return trip, Pastana and his colleagues were only able to find P. callipterus in the stream in which it was first discovered.

Researchers encountered the second new species documented on these field expeditions among tangles of tree roots protruding from the banks of muddy watered streams -- distinct from the relatively translucent, if darkly stained, black water streams. Given the scientific name P. rhizophilus for its love (phil) of roots (rhiz), this species is an amber yellow with males possessing dark streaks in their dorsal and anal fins. But perhaps the most distinctive quality of this new species is that it is so small that scientists consider it to be miniature, a designation given to any fish that is less than about an inch long when mature, Pastana said. He added that lab study revealed that in these three-quarter-inch-long fish, parts of the skeleton that are typically bone are instead made of cartilage.

Genetic investigations confirmed the evolutionary relationship of these two new closely related species and their relatives, bringing the total number of species in their small sub-family (Crenuchinae) to five. This is the first addition of a new species to the group in 57 years.

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Dynamic rivers contributed to Amazon's rich bird diversity

 One of the most contentious questions in evolutionary biology is, how did the Amazon become so rich in species? A new study focused on birds examines how the movements of rivers in the Amazon have contributed to that area's exceptional biological diversity. The research team, led by the American Museum of Natural History, found that as small river systems change over time, they spur the evolution of new species. The findings also reveal previously unknown bird species in the Amazon that are only found in small areas next to these dynamic river systems, putting them at high risk of imminent extinction. The study is detailed today in the journal Science Advances.

The lowland rainforests of the Amazon River basin harbor more diversity than any other terrestrial ecosystem on the planet. It is also a globally important biome containing about 18 percent of all trees on Earth and carrying more fresh water than the next seven largest river basins combined. Researchers have long wondered and hotly debate how the Amazon's rich biodiversity arose and accumulated.

"Early evolutionary biologists like Alfred Russel Wallace noticed that many species of primates and birds differ across opposite riverbanks in the Amazon, and ornithologists now know that rivers are associated -- in one way or another -- with the origin of many avian species," said the study's lead author Lukas Musher, a postdoctoral researcher at the Academy of Natural Sciences of Drexel University and a recent comparative biology Ph.D. graduate of the American Museum of Natural History's Richard Gilder Graduate School. "Moreover, accumulating geological evidence has suggested that these rivers are highly dynamic, moving around the South American landscape over relatively short time periods, on the order of thousands or tens of thousands of years."

To investigate how the movement of rivers across the landscape has influenced the accumulation of bird species in the Amazon, the researchers sequenced the genomes of six species of Amazonian birds.

"Even though birds can fly, our study confirmed that current rivers across the Southern Amazon rainforest, even relatively small ones, are highly effective at isolating populations of these six species, which leads to genomic divergence and ultimately speciation," said the study's senior author Joel Cracraft, Lamont Curator and curator-in-charge in the Museum's Department of Ornithology.

However, because these rivers move around the landscape at different time scales, their movements can have varying outcomes for bird species: when river rearrangements occur quickly, populations of birds on each side can merge before they've had time to differentiate; when river changes happen slowly, species have a longer time to diverge from one another; and when rivers change at intermediate rates, bird populations diverge and then join back together and co-occur when a river moves.

The scientists also identified distinct populations of birds that should be described as separate species but have been considered a single species until now.

"Though we know Amazonian biodiversity is unmatched by any other terrestrial ecosystem, we demonstrated that its species richness may be greatly underestimated even in well-studied groups such as birds," Musher said. "Our results corroborate those of other studies that have reported fine-scale patterns of diversity across the southern Amazon basin -- a region threatened by rapid and ongoing deforestation -- yet this diversity is generally unrecognized. Many of the distinct populations are relatively young and endemic to a small Amazonian region, meaning that a large portion of the Amazon's birds may be threatened with loss to imminent extinction."

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Amazon rainforest is losing resilience: New evidence from satellite data analysis

The Amazon rainforest is likely losing resilience, data analysis from high-resolution satellite images suggests. This is due to stress from a combination of logging and burning -- the influence of human-caused climate change is not clearly determinable so far, but will likely matter greatly in the future. For about three quarters of the forest, the ability to recover from perturbation has been decreasing since the early 2000s, which the scientists see as a warning sign. The new evidence is derived from advanced statistical analysis of satellite data of changes in vegetation biomass and productivity.

"Reduced resilience -- the ability to recover from perturbations like droughts or fires -- can mean an increased risk of dieback of the Amazon rainforest. That we see such a resilience loss in observations is worrying," says Niklas Boers from the Potsdam Institute for Climate Impact Research and the Technical University of Munich, who conducted the study jointly with researchers from the University of Exeter, UK.

"The Amazon rainforest is a home to a unique host of biodiversity, strongly influences rainfall all over South America by way of its enormous evapotranspiration, and stores huge amounts of carbon that could be released as greenhouse gases in the case of even partial dieback, in turn contributing to further global warming," Boers explains. "This is why the rainforest is of global relevance."

"When the tipping itself will be observable, it would be too late"

The Amazon is considered a potential tipping element in the Earth system and a number of studies revealed its vulnerability. "However, computer simulation studies of its future yield quite a range of results," says Boers. "We've therefore been looking into specific observational data for signs of resilience changes during the last decades. We see continuously decreasing rainforest resilience since the early 2000s, but we cannot tell when a potential transition from rainforest to savanna might happen. When it will be observable, it would likely be too late to stop it." The research is part of the project 'Tipping Points in the Earth System' (TiPES) funded by European Union's Horizon 2020 programme.

The team from the Potsdam Institute for Climate Impact Research and the Global Systems Institute of the University of Exeter used stability indicators that had previously already been applied to the Greenland ice sheet and the Atlantic overturning circulation. These statistical indicators aim at predicting the approach of a system towards an abrupt change by identifying a critical slowing down of the system's dynamics, for instance its reaction to weather variability. The analysis of two satellite data sets, representing biomass and the greenness of the forest, revealed the critical slowing down. This critical slowing down can be seen as a weakening of the restoring forces that usually bring the system back to its equilibrium after perturbations.

"A system might seem stable if one is considering only its mean state"

While a system might seem stable if one is considering only its mean state, taking a closer look at the data with innovative statistical methods can reveal resilience loss," says Chris Boulton from the University of Exeter's Global Systems Institute. "Previous studies based on computer simulations indicated that large parts of the Amazon can be committed to dieback before showing a strong change in the mean state. Our observational analysis now shows that in many areas destabilization indeed seems to be underway already."

To try and determine causes for the loss of resilience that the scientists find in the data, they explored the relation to rainfall in a given area in the Amazon, culminating in three 'once in a century' drought events in the region. Drier areas turn out to be more at risk than wetter ones. "This is alarming, as the IPCC models project an overall drying of the Amazon region in response to anthropogenic global warming," says Boers. Another factor is the distance of an area to roads and settlements from where people can access the forest. The data confirms that areas close to human land-use are more threatened.

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Declining biodiversity in wild Amazon fisheries threatens human diet

A new study of dozens of wild fish species commonly consumed in the Peruvian Amazon says that people there could suffer major nutritional shortages if ongoing losses in fish biodiversity continue. Furthermore, the increasing use of aquaculture and other substitutes may not compensate. The research has implications far beyond the Amazon, since the diversity and abundance of wild-harvested foods is declining in rivers and lakes globally, as well as on land. Some 2 billion people globally depend on non-cultivated foods; inland fisheries alone employ some 60 million people, and provide the primary source of protein for some 200 million. The study appears this week in the journal Science Advances.

The authors studied the vast, rural Loreto department of the Peruvian Amazon, where most of the 800,000 inhabitants eat fish at least once a day, or an average of about 52 kilograms (115 pounds) per year. This is their primary source not only of protein, but fatty acids and essential trace minerals including iron, zinc and calcium. Unfortunately, it is not enough; a quarter of all children are malnourished or stunted, and more than a fifth of women of child-bearing age are iron deficient.

Threats to Amazon fisheries, long a mainstay for both indigenous people and modern development, are legion: new hydropower dams that pen in big migratory fish (some travel thousands of miles from Andes headwaters to the Atlantic estuary and back); soil erosion into rivers from deforestation; toxic runoff from gold mines; and over-exploitation by fishermen themselves, who are struggling to feed fast-growing populations. In Loreto, catch tonnages are stagnating; some large migratory species are already on the decline, and others may be on the way. It is the same elsewhere; globally, a third of freshwater fish species are threatened with extinction, and 80 are already known to be extinct, according to the World Wildlife Fund.

Different species of animals and plants contain different ratios of nutrients, so biodiversity is key to adequate human nutrition, say the researchers. "If fish decline, the quality of the diet will decline," said the study's senior coauthor, Shahid Naeem, director of Columbia University's Earth Institute Center for Environmental Sustainability. "Things are definitely declining now, and they could be on the path to crashing eventually."

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 River docks, where wholesale commerce begins at 3:30 in the morning. He and another student bought multiple specimens of as many different species as they could find, and ended up with 56 of the region's 60-some main food species. These included modest-size scale fish known locally as ractacara and yulilla; saucer-shaped palometa (related to piranha); and giant catfish extending six feet or more. (The researchers settled for chunks of the biggest ones.)

The fish were flown on ice to a government lab in Lima, where each species was analyzed for protein, fatty acids and trace minerals. The researchers then plotted the nutritional value of each species against its probability of surviving various kinds of ongoing environmental degradation. From this, they drew up multiple scenarios of how people's future diet would be affected as various species dropped out of the mix.

Overall, the biomass of fish caught has remained stable in recent years. However, large migratory species, the most vulnerable to human activities, comprise a shrinking portion, and as they disappear, they are being replaced by smaller local species. Most fish contain about the same amount of protein, so this has not affected the protein supply. And, the researchers found, many smaller fish in fact contain higher levels of omega-3 fatty acids, so their takeover may actually increase those supplies. On the other hand, as species compositions lean more to smaller fish, supplies of iron, zinc are already going down, and will continue to decline, they say.

"Like any other complex system, you see a tradeoff," said Heilpern. "Some things are going up while other things are going down. But that only lasts up to a point." Exactly which species will fill the gaps left when others decline is difficult to predict -- but the researchers project that the overall nutritional value of the catch will nosedive around the point where 40 of the 60 food species become scarce or extinct. "You have a tipping point, where the species that remain can be really lousy," said Heilpern.

One potential solution: in many places around the world where wild foods including fish and bush meat (such as monkeys and lizards) are declining, people are turning increasingly to farm-raised chicken and aquaculture -- a trend encouraged by the World Bank and other powerful organizations. This is increasingly the case in Loreto. But in a separate study published in March, Heilpern, Naeem and their colleagues show that this, too, is undermining human nutrition.

The researchers observed that chicken production in the region grew by about three quarters from 2010 to 2016, and aquaculture nearly doubled. But in analyzing the farmed animals' nutritional values, they found that they typically offer poorer nutrition than a diverse mix of wild fish. In particular, the move to chicken and aquaculture will probably exacerbate the region's already serious iron deficiencies, and limit supplies of essential fatty acids, they say. "Because no single species can offer all key nutrients, a diversity of species is needed to sustain nutritionally adequate diets," they write.

Besides this, chicken farming and aquaculture exert far more pressure on the environment than fishing. In addition to encouraging clearing of forests to produce feed for the animals, animal farming produces more more greenhouse gases, and introduces fertilizers and other pollutants into nearby waters, says Heilpern.

"Inland fish are fundamental for nutrition in many low-income and food-deficit countries, and of course landlocked countries," said John Valbo Jørgensen, a Rome-based expert on inland fisheries with the UN Food and Agriculture Organization. "Many significant inland fisheries, including those of Peru, take place in remote areas with poor infrastructure and limited inputs. It will not be feasible to replace those fisheries with farmed animals including fish."

Heilpern is now working with the Wildlife Conservation Society to produce an illustrated guide to the region's fish, including their nutritional values, in hopes of promoting a better understanding of their value among both fishermen and consumers.

Read more at Science Daily