In the Peruvian Amazon, forests aren’t bouncing back after gold mining—not just because the soil is damaged, but because the land has lost its ability to hold water.
A new study shows that a common method called suction mining dries out the ground so badly that even planting new trees often doesn’t work.
The research, published in Communications Earth & Environment, helps explain why reforestation efforts in the region have largely failed.
Josh West, a professor of Earth sciences at the University of Southern California (USC), says this isn’t just about soil damage. “The mining process dries out the land, making it inhospitable for new trees,” he explains.
The study was led by scientist Abra Atwood from the Woodwell Climate Research Center. Atwood, who earned her PhD at USC, worked with researchers from several universities in the U.S. and Peru.
Together, they studied two abandoned mining sites in Peru’s Madre de Dios region, near the borders of Brazil and Bolivia.
To understand what’s happening, the team used drones, soil sensors, and underground imaging tools. They focused on suction mining, which is often used by small or family-run operations. This technique uses powerful water cannons to break apart the soil.
The loosened material is sent through filters to catch gold, while the nutrient-rich topsoil is washed away. What’s left behind are large, stagnant ponds and tall piles of sand—some as high as a three-story building.
Unlike other mining methods that may leave some topsoil intact, suction mining leaves behind very little that can support new plant life.
To measure how water moves through the soil, the researchers used a method called electrical resistivity imaging. They found that rainwater drains through these sand piles up to 100 times faster than in untouched forest soil. After it rains, these areas also dry out five times faster, making it nearly impossible for young tree roots to find water.
They also discovered that these damaged sites are much hotter than healthy forest areas. On the surface of exposed sand piles, temperatures reached up to 145°F (60°C)—about as hot as an oven. Even with efforts to plant new trees, the extreme heat and dryness cause the seedlings to die quickly.
Although the team saw some regrowth near ponds and low-lying spots, most of the mined land remained bare—especially the sandy areas far from the water table. These dry zones are the hardest places for forests to return.
Since 1980, small-scale gold mining has destroyed more than 95,000 hectares of rainforest in this region—an area over seven times the size of San Francisco. In protected areas like the Tambopata National Reserve, mining continues to expand, threatening wildlife and Indigenous communities. Gold mining now causes nearly 10% of all deforestation in the Amazon.
The researchers believe that simply planting trees won’t be enough. They suggest reshaping the land—flattening sand piles and filling in ponds—to help hold moisture and support new growth. Nature might eventually do this through erosion, but the process is far too slow.
“There’s only one Amazon,” says West. “It’s a unique and living system. If we lose it, we can’t get it back.”
