The effects of gold mining on forest health are long lasting. According to new research, gold mining stunts the regrowth of Amazon forests, limiting their ability to store carbon.

"Historically gold mining was often overlooked in deforestation analysis as it occupies relatively small areas when compared to pastures or large-scale agriculture," lead study author Michelle Kalamandeen told UPI in an email.

Kalamandeen started the research as a postgraduate researcher at the University of Leeds but is now a postdoctoral researcher at Cambridge University.

"Yet, given recent proliferation in mining activities since 2007-2008 and again in 2012, the potential areas may be underestimated and the impact on biodiversity and forest recovery unquantified," she said.

For the study, Kalamandeen and her colleagues sampled soil and measured trees at 18 test plots in two main gold mining areas in Guyana. Researchers also established two control sites in old-growth forests.

"We measured trees/saplings/seedlings within each plot and took soil samples from abandoned gold mining sites, active sites and control 'old-growth' sites," Kalamandeen said.

The data -- published Monday in the Journal of Applied Ecology -- showed trees in forests damaged by gold mining activity struggled to reestablish themselves. Where as forest harmed by other kinds of activities, such as logging and agriculture, were able to rebound, the negative effects of mining on growth and carbon storage persisted.

"Our analysis showed that the lack of nitrogen was the primary driving force for the lack of recovery occurring on the tailing ponds and mining pits," Kalamandeen said. "On the overburden, where there was an abundance of nitrogen, regrowth of trees were similar to other Neotropical secondary, recovery forests."

Researchers were surprised to find that a lack of nitrogen, instead of an excess of mercury, was to blame for the stunted regrowth.

"Our research showed that active mines had on average 250 times more mercury than abandoned mining sites, suggesting that this mercury leaches into neighboring forests and rivers," Kalamandeen said.

Researchers found that in the few mining sites where topsoil was replaced and fertilized with nitrogen -- an often mandated, but rarely enforced, restoration step -- regrowth was comparable to plots where trees were cleared for other types of activity.

Scientists hope their findings will inspire politicians and policy makers in the Amazon to strengthen environmental regulations for gold mining.

"It's important the current environmental policies are enforced. Most Amazonian countries have reasonable monitoring and enforcement policies but weakening of such policies or reduced funding to regulatory agencies as we've seen in Brazil and Venezuela, means that enforcement isn't occurring," Kalamandeen said.

"Addressing corruption in mining agencies is also another issue that needs addressing at the national scale," Kalamandeen said. "For restoration, many Amazonian countries don't have a forest restoration policy when it comes to gold mining and this needs to be tested and developed for tropical forests at the landscape-scale."

Gold prices often rise in the wake of economic crises, and when they do, small-scale gold mining activity ramps up in the Amazon.

Though under new leadership, Brazil has recently been weakening environmental regulations. But in the years that followed the financial crisis, strong rainforest protections forced miners to pursue gold in neighboring countries, especially the dense forests of Guyana and the French Guiana.

With the COVID-19 pandemic putting a significant dent in global economic growth, researchers worry gold mining activity will once again proliferate across a large stretch of forest known as the Guiana Shield. In the future, scientists hope to test new technologies designed to curb the threat of gold mining.

"We hope to use remote sensing to help detect gold mining especially illegal mining within the Amazon," Kalamandeen said.

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