Why forests aren’t coming back after gold mining in the Amazon
Key findings:
- Scientists found that small-scale gold mining in the Peruvian Amazon is stripping away topsoil and reshaping the land in ways that deplete water — a key reason forests fail to grow back.
- The process leaves behind hot, dry piles of sand and stagnant ponds. These sandy mounds can reach 145 degrees F (60 C) and drain water up to 100 times faster than forest soil, making the terrain inhospitable to tree growth.
- Sites near ponds or at lower elevations retain more moisture and show signs of natural regrowth, suggesting that water access — not just soil quality — plays a critical role in forest recovery.
- To improve reforestation, the researchers recommend flattening the sand piles and filling in mining ponds so plant roots can reach the water table more easily.
Forests in the Peruvian Amazon aren’t growing back after gold mining — not just because the soil is damaged from toxic metals, but because the land has been depleted of its water. A common mining method known as suction mining reshapes the terrain in ways that drain moisture and trap heat, creating harsh conditions where even replanted seedlings can’t survive.
The findings, published in Communications Earth & Environment, revealed why reforestation efforts in the region have struggled. One of the study’s co-authors is Josh West, professor of Earth sciences and environmental studies at the USC Dornsife College of Letters, Arts and Sciences.
“We’ve known that soil degradation slows forest recovery,” said West, who is also a National Geographic Explorer. “But this is different. The mining process dries out the land, making it inhospitable for new trees.”