Gold Mining Is the Latest Human Effort to Wreak Havoc on the Amazon

Illegal logging, slash-and-burn farming, and the steady pace of infrastructure development are all contributing to the decline of the Amazon. A new mapping effort has revealed a new threat: Gold mining in the Peruvian Amazon, once thought to be a relatively small industry, has skyrocketed. With it has come increased reliance on child labor, conflict, and the loss of tens of thousands of hectares of rainforest.

Since the 2008 global recession, deforestation rates attributable to gold mining have tripled in Peru's section of the Amazon, according to the results of an aerial survey published in PNAS. The team further found that the total geographic being used by miners increased by 400 percent from 1999 to 2012.

"Our results reveal far more rainforest damage than previously reported by the government, NGOs, or other researchers," said lead author Greg Asner, of the Carnegie Institution for Science, in a release. "In all, we found that the rate of forest loss from gold mining accelerated from 2,166 hectares per year before 2008 to 6,145 hectares each year after the 2008 global financial crisis that rocketed gold prices."

As Asner notes, that's higher than previous estimates in the Madre de Dios region, where gold mining operations have increased steadily with rising global gold prices. For example, a 2011 study published in PLOS One found an average deforestation rate of 1915 hectares per year from 2006 to 2009.

The increase in the new study may be due to more sophisticated mapping techniques. The team used the Carnegie Landsat Analysis System-lite (CLASlite) land-mapping system, which has higher resolution than traditional Landsat satellite survey systems. As the authors write:

CLASlite differs from other satellite-mapping approaches because it uses spectral mixture analysis to detect changes in forest cover in increments as small as 1% of a Landsat pixel, or about 10 m2. This process allows for the detection and mapping of fine-scale disturbances that go undetected using traditional remote-sensing methods

The higher resolution meant the team was able to better account for smaller mining operations, which tend to be the hardest to regulate and track. According to the team's findings, "Small clandestine operations now comprise more than half of all gold mining activities throughout the region."

Those small operations can still be highly destructive, especially when added up as a whole. Aside from cutting down forests and destroying fragile topsoil to get at gold, miners rely on toxic chemicals like mercury to separate gold from earth. The 2011 study noted above actually focused on imports of mercury to Peru, and found that mercury demand in the country rose with gold prices, which likely means more mercury in the Amazonian system.

According to Asner's team, "recent quantitative work also shows very widespread mercury pollution in air and waters throughout Madre de Dios, negatively affecting the entire food chain and people far beyond the mining sites." Mercury is not only highly poisonous, which is bad news for already damaged systems. It's also incredibly persistent. A study published in the same issue of PNAS found that mercury used during California's gold rush in the mid-19th century will likely persist for thousands of years.

There's another problem with Peru's gold mining: much of it's illegal. That quest for gold has brought about criminal interests and violence, as our Jason Koebler recently detailed. "About one-fifth of the country's gold is produced illegally, and the sector is propped up with forced labor and child labor," he wrote. For a country already dealing with a huge cocaine problem, it's yet another industry full of dirty money that's a cesspool for corruption.

Anser et. alnote that high-resolution airborne and satellite mapping is key to quantifying deforestation and harmful anthropogenic effects on the Amazon, which is true. But for things to change, that data has to be utilized by lawmakers and enforcers to try to bring things under control.

"Obtaining good information on illegal gold mining, to guide sound policy and enforcement decisions, has been particularly difficult so far," said co-author Ernesto Raez Luna of the Peruvian Ministry of the Environment in the same release. "Finally, we have very detailed and accurate data that we can turn into government action. We are using this study to warn Peruvians on the terrible impact of illegal mining in one of the most important enclaves of biodiversity in the world, a place that we have vowed, as a nation, to protect for all humanity. Nobody should buy one gram of this jungle gold. The mining must be stopped."

How that will be done remains to be seen. Until then, the Amazon will continue to fall under the weight of human progress, including urbanization, oil drilling, and megadroughts. Now we can add mining to the ever-growing list.

@derektmead