Mining companies worldwide are expanding mineral extraction at existing mines, as the rate of opening new sites slows, to meet global demand driven mainly by the need for clean energy infrastructure.
A study, publishing January 22 in the Cell Press journal One Earth, shows that the practice of expanding and intensifying mining at existing sites can worsen environmental and social risks over time. But these operations tend to draw less scrutiny and regulation.
"Current policy and debate are focused on approving new critical mineral mines," says first author Deanna Kemp of the University of Queensland, Brisbane, Australia. "That is important, but our study draws attention to a deeper shift, which is the ongoing expansion of existing mines and the long-term environmental and social liabilities this creates."
Global demand for minerals has been rising over the past decades, often because of their central roles in the renewable energy transition. Metals like copper, cobalt, and lithium are key components of electric vehicles, power grids, and batteries. Some estimates suggest that the need for these minerals could increase by as much as six times by 2040.
To meet such demand, mining companies around the world are increasingly turning to brownfield mining, which involves exploring and extracting minerals at or near existing operations for longer periods and at deeper levels. Such practice tends to generate more waste, take up more land, and lead to greater overall impact in these places. Unlike new mining projects, which can take up to 15 years to permit and develop, brownfield expansion often unfolds with less public scrutiny.
While brownfield mining is common industry practice, its sheer scale, pace, and impact remained poorly understood at the global level.
To address this gap, Kemp and her team used data on global mineral production and investment to show how capital has been increasingly flowing to brownfield mining. They identified 366 brownfield sites around the world for further analysis.
By mapping these operations with satellite imagery and other data that tracks social and environmental conditions worldwide, the team found that more than one-fifth of the sites lie within 50 kilometers (31 miles) of ecologically pristine or partially modified areas, including Arctic tundra regions and high-mountain environments. More than half of the sites are located within 20 kilometers (12 miles) of biodiversity hotspots or protected areas, potentially posing threats to sensitive ecosystems.
The team also found that many brownfield operations are concentrated in countries facing high levels of structural inequality, where access to opportunities like education and employment varies across groups. More than a third of the brownfield sites they identified are in countries affected by conflict or militarization.
Overall, nearly 80% of the brownfield mines analyzed are in locations facing multiple high-risk conditions, which also include water scarcity, weak governance, and limited press freedom.
"What stood out to us is that many of these mines are operating in contexts with layers of social and environmental complexity," Kemp says. "These are conditions where regulatory oversight is harder while risks accumulate."
Kemp adds that with new mining technologies, some brownfield expansions are happening underground, and they are difficult to detect and evaluate with satellite imagery. As a result, the team's findings may underestimate the extent of such industrial expansion.
"If larger, deeper, and longer-life mines is how we move the energy transition forward, our regulatory frameworks should better reflect that practice," Kemp says. "That means assessing mine expansion for cumulative and long-term effects rather than treating expansion as a routine decision compared to new projects."
