A recent Nature study titled “Biomass carbon emissions from nickel mining have significant implications for climate action” reveals that current research and database metrics vastly underestimate the environmental impact of nickel mining. Specifically, the study found that the land use associated with nickel mining has been understated by a factor of 4 to 500.
This has serious implications for climate mitigation efforts, especially since the land being disturbed is typically dense with carbon-rich biomass. Currently, mining companies do not count emissions caused by biomass losses in their Scope 1 or 3 sustainability reporting despite the fact that, as noted in the study, rehabilitation efforts in areas with ultramafic rock have been largely unsuccessful (tropical nickel deposits).
With nickel mining currently unavoidable, Dr. Mervine said the research highlighted a need for mining companies to avoid developing new mines in areas where there is “irrecoverable carbon”—carbon stored in ecosystems such as old-growth rainforests and mangroves, which once cut down can never be restored back to their original biomass densities. Link
Importantly, the authors acknowledge that even these revised figures are likely to underestimate land use and carbon impact, as the study only accounts for direct land transformation—excluding the far-reaching indirect impacts.
Separate studies suggest that indirect deforestation from mining can expand a mine’s total footprint by 7 to 28 times. These indirect impacts include land used for infrastructure such as roads, ports, power stations, housing, markets, and new agricultural zones that emerge around mining operations.
When these direct and indirect impacts are combined, the true land and carbon footprint of nickel mining could be underestimated by as much as 28x to 14,000x, far beyond the 4x to 500x noted in Nature. To give these figures some context, the study notes that the mining industry already accounts for roughly 10% of global energy-related carbon emissions. In addition, biomass carbon losses in some cases are as large as emissions from extraction and processing according to the authors – and would likely be larger than these activities when indirect impacts are considered.
This trend is likely to apply to other energy transition metals to varying degrees.
By contrast, nodule extraction from the deep ocean avoids these issues almost entirely. Its indirect impacts are well studied and primarily involve sediment plumes. Unlike land-based mining, there is no forest or vegetation at the bottom of the ocean, and the amount of living biomass disturbed is orders of magnitude lower than on land. Moreover, research shows that plume-related impacts on biomass are minimal to negligible.
This new data only strengthens the case for nodule harvesting. We already knew based on life cycle analyses that it outperforms terrestrial mining across nearly every impact metric. This study makes it clear that the gap is even wider in terms of land use and climate impact.
More subtly, this work underscores how much uncertainty still surrounds terrestrial mining, despite thousands of years of experience. Arguments that we should halt deep-sea mining due to uncertainty appear increasingly weak, especially when terrestrial mining’s known risks are so severe (especially to indigenous human populations).
Finally, greater land use also translates to greater threats to people and biodiversity. Communities in Africa and Southeast Asia face genocide, war, disease, displacement, and malnutrition thanks in no small part to our push to extract increasingly lower grade ores from tropical rainforests. These forests, which host massive biodiversity, are equally under threat.
Activists who seek to block nodule harvesting while ignoring the catastrophic human and environmental toll of terrestrial mining are disingenuous and their motivations suspect. History will not be kind to these groups.
“Companies should prioritize the development and expansion of mine sites in areas that have low biomass densities, such as in deserts, rather than in rainforests, while, of course, being mindful of environmental impacts beyond carbon.” Link
(we note that the abyssal plains have been compared to deserts by scientists)