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Alarming levels of mercury found in aging Amazon forest

The protected old-growth forest in the southeastern Peruvian Amazon appears pristine: Old trees with massive trunks grow alongside young, slender trunks, forming a canopy so thick that scientists sometimes feel It feels like night in the daytime.

But a new analysis of what’s inside forest leaves and bird feathers tells a different story: The same canopy that supports some of the richest biodiversity on the planet is also sucking in toxic levels of mercury. alarming, according to a study published Friday.

Mercury is released into the air by miners searching for gold along nearby riverbanks. They use mercury to separate the precious metal from the surrounding sediment and then burn it. Carried in the air, the particles cling to the leaves like dust and are washed away by rain to the forest floor. Other seeds are attracted to the leaf tissue. From there, the mercury appears to have made its way up the songbird food web, which indicates mercury levels 2 to 12 times higher than in comparable areas far from mining.

“The patterns are much clearer and more devastating than we expected,” said Jacqueline Gerson, a biochemist at the University of California Berkeley who led the study as a PhD. will be find. student at Duke. Research is published in the journal Nature Communications.

The findings, from the Madre de Dios region of Peru, provide new evidence of how humans are changing ecosystems around the world, as species extinction rates accelerate, with little understanding. about consequences.

Scientists have known for a long time that mercury, which is also released into the air when coal is burned, is a neurotoxin dangerous to humans and animals. In aquatic ecosystems, it can be easily converted into a highly toxic form known as methylmercury. When larger fish eat smaller fish, mercury will stick around, accumulating in food webs. For this reason, doctors advise pregnant women around the world to avoid eating large, carnivorous fish such as shark, mackerel, and swordfish.

In the region of Madre de Dios, where illegal gold mining has skyrocketed In recent years along with gold prices in the global market, the government declared a health emergency in 2016 after 40% of people were tested in 97 villages for dangerously high levels of mercury. in their system.

The researchers mainly focused on human exposure to mercury in rivers, lakes and oceans. They don’t worry about it on land, because it’s less likely to become mercury. But the sheer amount of mercury that goes into the forest, combined with rain and soil conditions, is leading to worrying levels of methylmercury there.

“It is thought that people living in the Peruvian Amazon have been exposed to mercury from eating fish,” Dr. Gerson said. “That may not be the case.”

The type of gold mining that occurs in the Madre de Dios region, known as manual and small-scale gold mining, occurs in about 70 countries, often illegally or informally, and it is largest source of mercury pollution in the world. It also accounts for about 20% of global gold production.

Julio Cusurichi Palacios, president of the Indigenous Federation of the Madre de Dios River and its Tributaries, a group formed by indigenous communities in the area, said the government should combat illegal fishing with coercion. but also by enhancing alternative livelihoods for indigenous peoples and other local people. He says they harvest fish, Brazil nuts, yucca and corn, but need help “improving their merchandise, selling their merchandise, so they don’t have to think,” I better. go mining, because my product has no market.'”

For the study, Dr. Gerson and her team collected soil, leaves, forest litter and other samples at three sites near the mining operation and two more distant. To collect a certain number of leaves, they use a giant slingshot to shoot a weighted rope into the canopy and pull the branch down.

As mercury levels returned, a protected former development near gold mining became prominent. Those areas had 15 times more mercury than neighboring areas, probably because the thick canopy of trees and vegetation captured and stored the mercury.

Shocked by the numbers, Dr. Gerson continued to scour the scientific literature for examples of forests of similar magnitude. The only one she found was in an industrial area in Guizhou, China, contaminated by mercury mining and coal burning. Some levels in the Amazon classic look healthy even higher.

By capturing mercury, forests are helping to keep it out of aquatic systems, says Emily Bernhardt, a professor of biochemistry at Duke University and a co-author of the study.

“These are some of the most biodiverse forests on Earth,” said Dr. Bernhardt. “We already know that they sequester tons of carbon in their biomass and soil, and now we’ve discovered a hugely important, additional service.”

But service is not without cost. She notes that mercury poisoning can affect a bird’s ability to navigate and sing, and may cause them to lay fewer eggs. It can also make their eggs less likely to hatch.

Previously, scientists had assumed that mercury pollution in the air from this type of gold mining would have less of a local effect, said Daniel Obrist, a professor of environmental science at the University of Massachusetts Lowell, who has studied study mercury in the forests of the Northeastern United States and the Arctic, said. and did not participate in the Amazon research.

“It fills a very important gap in understanding what happens there with small-scale mining and what its impact is,” Dr. Obrist said. “Not just for global processes, but for local communities.”

https://www.nytimes.com/2022/01/28/climate/amazon-forest-mercury-peru.html Alarming levels of mercury found in aging Amazon forest

Fry Electronics Team

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