(CNN) One autumn day in 2009, the price of gold topped $1,000 an ounce.

That nice, round number brought cheers on London trading floors and toasts in Manhattan bars, but it made a different noise in "Mother of God," Peru.

Madre de Dios is a pristine chunk of the Amazon about the size of South Carolina, where macaws and monkeys, jaguars and butterflies thrive. It is some of the healthiest rainforest left on Earth and here, that $1000 number brought the sound of chain saws, diesel pumps and dirt bikes.

The Peruvian government estimates that hundreds of square miles of pristine rain forest in Madre de Dios have been to turned into toxic wasteland by illicit gold mining.

It created jungle boomtowns, complete with pop-up brothels and gun fights, as tens of thousands of men from the poorest corners of Peru joined a modern gold rush.

Much like the '49ers sluiced for treasure in California more than 150 years ago, these miners use primitive methods involving mercury. Most don't fully understand that "quicksilver" is toxic to every form of life in the Amazon. Or that since they fish the same waters they mine, it can end up in their own bloodstream, causing a host of health problems.