Rings can tell you a lot more about a tree than just its age.
Get the Popular Science daily newsletter💡 Email address Sign up Thank you! Terms of Service and Privacy Policy. Researchers believe they have identified a network of spies to help combat illegal gold mining operations in the Amazon rainforest. But unlike other espionage efforts, there is no risk of betrayal from the new assets: Trees aren't known for spilling secrets. Humans have coveted the Amazon's natural resources for generations, particularly its gold. But with most of the region's easily accessible precious metals long gone, illegal mining operations now focus on extracting the soil's hidden gold particles. To do this, the miners use a method that requires adding toxic mercury into the ground and allowing it to bind to any surrounding gold. Because the resulting amalgams have a much lower melting point than gold alone, miners then burn the mercury away to collect the residual lucrative metal. Meanwhile, the mercury-laden smoke disperses into the atmosphere where it can harm the surrounding…