Fig trees tell tales on illegal miners

FIG trees could give researchers the inside track on whether international efforts to prevent mercury emissions are working after it was discovered their rings can be used to monitor pollution from illegal gold mining.

Artisanal miners use toxic mercury to recover gold from ore. Mercury is often then dumped into the environment or burned off. This practice occurs predominantly in the Amazon and tropical areas in Southeast Asia.

Artisanal mining has taken place in Peru for centuries, particularly in the Madre de Dios region, where more than 30,000 small-scale mining operations are responsible for most of the country’s gold production. They have been described as a “scourge” because of the deforestation and mercury pollution they cause.

Research led by Cornell University in the US has found that fig trees growing in the region absorb mercury and record the concentrations in their rings. The finding suggests the trees could provide researchers with a network of biomonitors to track how regional use of mercury changes over the years.

Monitoring currently relies on devices that either need power to pump air or passive samplers that cost US$100 each and only last a couple of months.

“We’re trying to reduce emissions, especially from gold mining, as part of the United Nations Minamata Convention on Mercury, and in order to do that, we need to be able to measure it, to see the impact over time,” said study author Jacqueline Gerson, assistant professor of biological and environmental engineering at Cornell.

“This really offers a method that can be employed throughout the Global South to understand changes in mercury over time, as well as spatial indicators of mercury.”

The research is published in Frontiers in Environmental Science.