Amazon forests suck up mercury from gold supply chain

Scientists in the Amazon have discovered the highest levels of mercury ever recorded in the canopy of a pristine patch of old-growth rainforest, according to a study in Nature Communications.

Birds from the area, around Peru’s Los Amigos Biological Station, have 12 times the normal levels of mercury in their systems, according to the Duke University team.

“These forests are doing an enormous service by capturing a huge fraction of this mercury and preventing it from getting to the global atmospheric pool,” Duke biology professor Emily Bernhardt said in a statement.

That made it “even more important that they not be burned or deforested, because that would release all that mercury back to the atmosphere,” she added.

The Amazon is in the midst of a highly destructive gold mining boom, fueled by rising gold demand — the precious metal is essential, for example, in high tech. Gold prices stand at $1,800 an ounce, nearly four times where they were in 2001.

Those prices has pulled waves of miners to the fringes of the Amazon and has made Peru the world’s No. 6 gold producer. 

The mining has created scars in the jungle visible from space, according to NASA’s Earth Observatory.

Mercury is involved as miners work to recover small bits of gold in sediment. Mercury is also a neurotoxin that grows more and more concentrated as it moves up the food chain into predator fish and ultimately people.

One Brazilian study recommended that Amazonians in mining areas eat some predatory fish less than once a month, and a previous Duke study found 62 percent of the region’s population had mercury levels higher than the Environmental Protection Agency threshold.

Those studies were focused on water pollution. Friday’s Duke study, by contrast, looked up to the canopy. Researchers fired slingshots into the canopy and brought down leaves, which they sampled for mercury.

The result was dramatic.

“We found that mature Amazonian forests near gold mining are capturing huge volumes of atmospheric mercury, more than any other ecosystem previously studied in the entire world,” lead researcher Jacqueline Gerson of the University of California, Berkeley said in a statement. 

Once in the trees, the mercury did not all stay put. Researchers found elevated concentrations in the feathers of three songbird species deep in a nearby reserve, and far from mining activity. 

What should be done? Gerson, the lead researcher, said she doesn’t want mining to be shut down.

“A very similar thing, with very similar methods, has already been done throughout many of the wealthy countries of the world where gold was available. The demand is just pushing mining further into new areas.” 

The United States can’t stop them or “impose solutions,” Gerson said in a statement.

“The goal is to highlight that the issues are far vaster than water pollution, and that we need to work with local communities to come up with ways for miners to have a sustainable livelihood and protect indigenous communities from being poisoned through air and water,” she added.