The classic view of weathering as a stabilizing feedback traces back to influential work in the 1980s and 1990s. Robert Berner and colleagues formalized how silicate weathering responds to atmospheric carbon dioxide and temperature, creating a negative feedback loop: more carbon dioxide warms the planet and acidifies rain, which accelerates weathering, which in turn removes carbon dioxide from the atmosphere. Later, Maureen Raymo and William Ruddiman proposed that the uplift of mountain ranges such as the Himalaya may have cooled the Cenozoic Earth by exposing fresh rock to erosion. Francis Macdonald and colleagues later connected arc volcanism and associated weathering to major climatic transitions. These frameworks cemented the idea that mountain building and rock exposure are, in broad strokes, allies of a cool climate.

But as Bufe emphasizes, drawing down carbon dioxide is only one side of the ledger. Weathering and erosion also release carbon. The oxidation of fossil organic carbon buried in sedimentary rocks, and the oxidation of sulfide minerals such as pyrite, both deliver carbon dioxide to the atmosphere, in some landscapes at rates that rival or exceed the silicate weathering sink. Recent work by Bufe, Jeremy Rugenstein and Niels Hovius, published in Science in 2024, compiled global evidence that mountain ranges act not merely as carbon sinks but as carbon sources as well, with the balance between drawdown and release depending on what the rocks are made of, how fast they erode, and how water moves through them. In the Southern Alps of New Zealand, for example, rapid erosion of carbon-rich sedimentary rock can push the net carbon balance toward emission, whereas volcanic arcs dominated by fresh basalt tend to favor drawdown.

The picture grows still more complicated when biology and hydrology enter the equation. Susan Brantley and colleagues showed in 2023 that the depth and structure of the critical zone, the weathered skin of Earth where rock, soil, water and life interact, exert fundamental control on how much mineral surface area is available for reactions. Vegetation, microbial communities and soil organic matter can both accelerate mineral dissolution and shield it from infiltrating water. Meanwhile, organic carbon itself is constantly being eroded from soils, transported by rivers, buried in floodplains and deltas, or oxidized back to carbon dioxide. Studies led by Robert Hilton and A. J. West have mapped this biospheric carbon loop, and work by Guillaume Soulet and colleagues has quantified how efficiently the biosphere exchanges carbon with the atmosphere through erosion, complicating any simple accounting of weathering as a one-way carbon pump. Sue Tank and colleagues have further shown that in high-latitude permafrost landscapes, the fate of weathering-derived carbon in streams and lakes can shift dramatically as climates warm.

Spatial scale matters profoundly. A weathering flux measured on a single hillslope may not scale linearly to a whole catchment, and catchment-scale estimates may not extrapolate to mountain belts or continents. Supply of fresh mineral surface, runoff, temperature and lithology each impose their own dependencies, and these dependencies can switch sign across environments. In hot, wet tropical basaltic terrains, weathering rates can be extraordinarily high and largely supply-limited. In cold, arid or transport-limited settings, the same mineralogy may weather sluggishly. Time introduces its own twists: pulses of tectonic uplift or glacial grinding expose fresh rock that weathers rapidly at first, then slows as easily dissolved minerals are exhausted. Over million-year timescales, these transients mean that today’s weathering fluxes partly reflect climate and tectonics from deep in the past, making it treacherous to read modern weathering rates as a simple response to modern conditions.

Disciplinary boundaries compound the challenge. Geochemists who trace dissolved ions in rivers, geomorphologists who measure erosion and sediment transport, soil scientists who study profile development, ecologists who quantify vegetation dynamics and carbon cycling, and climate modelers who simulate global feedbacks each hold pieces of the puzzle. Bufe argues that only research spanning spatial scales, temporal scales and disciplines can resolve how weathering modulates the carbon cycle in a warming world. As the climate changes, weathering itself will change: rising temperatures and altered hydrology will accelerate some reactions, thawing permafrost will expose new mineral surfaces and release ancient organic carbon, and intensifying storms will mobilize sediment in ways that models are only beginning to capture. Whether the geological thermostat will help blunt anthropogenic warming, and on what timescale, remains an open and consequential question.

It is against this backdrop of genuine scientific uncertainty that Bufe levels his sharpest critique. Enhanced rock weathering, the practice of spreading crushed silicate rock such as basalt on farmland to accelerate carbon dioxide drawdown, has surged in popularity as a carbon removal strategy. A growing industry now sells carbon credits based on the assumption that a quantifiable and permanent fraction of the applied rock dissolves, and that the resulting bicarbonate represents durable carbon sequestration. Commercial rankings of the best enhanced weathering credit projects have proliferated, and the market is expanding faster than the underlying science can constrain it. In a companion review in Nature Reviews Earth & Environment, Maximilian Schiedung and colleagues catalogued the substantial uncertainties in measuring, reporting and verifying enhanced weathering outcomes, from dissolution kinetics in real soils to secondary carbonate formation that can return carbon to the atmosphere.

Bufe contends that issuing carbon credits for enhanced weathering at the present stage is premature. The very complexities that make natural weathering hard to quantify, the competing sources and sinks, the dependence on lithology, hydrology, biology and timescale, apply with full force to engineered deployments. Crushed rock applied to one field may behave very differently from the same material in another, and the net climate benefit must account for the carbon cost of mining, grinding and transporting rock, as well as for nitrous oxide and other greenhouse gas effects that soil amendments can trigger. Without robust, context-specific measurement of how much carbon is actually drawn down and for how long, credits risk monetizing an assumption rather than a verified outcome, potentially undermining confidence in carbon removal as a whole.

None of this argues that enhanced weathering should be abandoned, Bufe stresses. Rock weathering remains one of the most promising and scalable negative-emissions pathways, rooted in a process that has regulated Earth’s climate for eons. But realizing that promise responsibly demands investment in the fundamental science: long-term field experiments across climates and soil types, improved tracers of mineral dissolution and carbon fate in rivers and oceans, and models that honor the tangled interplay of tectonics, erosion, hydrology and life. The geological thermostat is real, but it is not a simple dial. Understanding its gears, and the directions in which some of them spin backward, is a prerequisite for turning rock weathering into a trustworthy tool against climate change rather than a cautionary tale about moving faster than the science.

Subject of Research: The complex role of rock weathering in Earth's carbon cycle and the risks of premature carbon crediting for enhanced weathering

Article Title: Rock weathering’s tangled role in Earth’s carbon cycle

Article References: Bufe, A. (2026). Rock weathering’s tangled role in Earth’s carbon cycle. Nature Water. https://doi.org/10.1038/s44221-026-00707-9

Image Credits: AI Generated

DOI: 10.1038/s44221-026-00707-9

Keywords: rock weathering, carbon cycle, enhanced weathering, carbon credits, chemical weathering, silicate minerals, carbon dioxide removal, geomorphology, biogeochemistry, erosion, climate mitigation, Nature Water

Enhanced rock weathering has long been touted as one of the most promising carbon removal strategies because it leverages a process that has regulated Earth’s climate for billions of years. When rainwater, slightly acidified by dissolved carbon dioxide, percolates through silicate rocks such as basalt, the carbonic acid pulls calcium and magnesium ions out of the mineral lattice. These ions ultimately combine with carbonate in oceans and soils, forming stable minerals that sequester carbon for tens of thousands of years or longer. The catch is speed: natural weathering operates on geological timescales, and even crushed and spread basalt can take years to decades to absorb a meaningful fraction of the carbon dioxide applied to farmland alongside it.

The new study attacks that bottleneck at its chemical root. Siderophores are small organic molecules with an extraordinary affinity for iron, capable of prizing the metal out of mineral surfaces even at vanishingly low concentrations. In doing so, they destabilize the crystal structures of iron-bearing silicates, exposing fresh surfaces to attack by carbonic and organic acids. Microbiologists have understood this mechanism for decades, but the idea of engineering microbes to produce siderophores at industrial scale for climate purposes remained largely theoretical—until now.

The research team used synthetic biology tools to upregulate the biosynthetic gene clusters responsible for siderophore synthesis in their bacterial strain, carefully balancing the metabolic burden that enhanced production imposes on the cells. Overproducing secondary metabolites can cripple microbial growth, so the engineering had to thread a needle between maximizing output and keeping the organisms viable. The resulting strains secreted siderophore concentrations several times higher than wild-type counterparts, and when applied to crushed basalt in controlled experiments, the treated microbial communities accelerated mineral dissolution rates well beyond what natural weathering achieves.

Measurements of dissolved ions released from the rock confirmed that the engineered bacteria were genuinely driving enhanced weathering rather than simply growing more prolifically. Elevated concentrations of calcium, magnesium, and silicon in solution served as chemical fingerprints of accelerated mineral breakdown. The researchers also tracked the fate of the released cations, which are the direct precursors of the carbonate species that permanently store carbon dioxide, providing a quantitative link between microbial activity and the theoretical carbon removal potential of the system.

What makes the approach especially attractive is its compatibility with existing agricultural practice. Enhanced rock weathering proposals typically involve spreading crushed basalt—a byproduct of mining and quarrying industries—across croplands, where it can also supply nutrients and raise soil pH. Adding engineered bacteria or their siderophore products to this workflow requires no new land, no exotic infrastructure, and no dramatic change in farm operations. The biological catalyst simply boosts the yield of carbon removal per tonne of rock applied, improving the economics of a scheme whose costs have otherwise been dominated by the grinding and transport of stone.

The carbon math is compelling if the laboratory results translate to the field. A single tonne of basalt can, in principle, absorb on the order of hundreds of kilograms of carbon dioxide over its weathering lifetime. If microbial siderophores can compress that timeline or increase the fraction of rock that fully dissolves, the effective carbon removal capacity of each tonne of applied rock rises accordingly, and with it the viability of gigatonne-scale deployment scenarios that climate models suggest will be necessary alongside deep emissions cuts.

Significant hurdles remain before engineered weathering microbes see real-world deployment. Field soils are wildly heterogeneous environments where introduced strains face competition from established microbial communities, predation, and fluctuating moisture and temperature. Regulators will also demand rigorous assessment of any genetically modified organism released into open agricultural systems, and researchers will need containment strategies or self-limiting designs to address ecological concerns. The team acknowledges that scaling from petri dishes and reactor columns to windswept fields is the defining test ahead.

Still, the study marks a striking convergence of biotechnology and geoscience, suggesting that the tools of synthetic biology can be pointed not merely at medicines and materials but at the planet’s own climate-regulating chemistry. If follow-up field trials vindicate the laboratory findings, the humble bacterial molecules that microbes have used for eons to feed on rock-bound iron could become one of the cheapest levers available for scrubbing carbon dioxide from the sky—and a vivid reminder that some of the most powerful climate technologies may already be alive in the soil beneath our feet.

Subject of Research: Engineered bacterial siderophore production for enhanced silicate rock weathering and carbon dioxide removal

Article Title: Engineered bacterial siderophore production accelerates rock weathering for carbon removal

Article References: Dalvie, N. C., Jalihal, A. P., Fitzgibbon, A., Böhnke, J.-T., Hijaz, M., Justman, Q. A., Davis, S. J., Silver, P. A., & Springer, M. (2026). Engineered bacterial siderophore production accelerates rock weathering for carbon removal. Nature Biotechnology. https://doi.org/10.1038/s41587-026-03288-w

Image Credits: AI Generated

DOI: 10.1038/s41587-026-03288-w

Keywords: enhanced rock weathering, siderophores, carbon removal, synthetic biology, basalt, silicate minerals, carbon dioxide sequestration, soil microbiology, climate engineering, mineral dissolution, biogeochemistry, Nature Biotechnology