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Nature https://doi.org/10.1038/s41586-020- be considered for use in preventing future out- 2381-y (2020). This article was published online on 22 June 2020. breaks of related animal viruses, if they make the leap to causing infection in humans. Environmental science Ultimately, it seems unlikely that a robust treatment for COVID-19 will rely on a single antibody. Rather, as was the case for SARS, Atmospheric CO removed a synergistic approach combining different 2 monoclonal antibodies in an antibody cocktail might be more effective5. For such approaches by rock weathering to move forwards, evidence of effective anti- body neutralization from in vitro studies will Johannes Lehmann & Angela Possinger be needed, along with in vivo data assessing how well an antibody can boost other aspects Large-scale removal of carbon dioxide from the atmosphere of the immune response — by enlisting other might be achieved through enhanced rock weathering. It now immune cells to tackle the infection, for exam- seems that this approach is as promising as other strategies, ple. There are many promising avenues to explore in these efforts. in terms of cost and CO2-removal potential. See p.242 Pinto and colleagues got a head start with their work by exploring pre-existing anti- bodies, and they should now have more B-cell Achieving targets for mitigating global risks, such as the possible release of metals and populations to mine. Many other teams, to warming will require the large-scale withdrawal persistent organic compounds (compounds give just some examples2,6–13, have also pre- of carbon dioxide from the atmosphere. On resistant to environmental degradation). sented useful discoveries in the hunt for page 242, Beerling et al.1 report that enhanced Despite the enthusiasm the authors’ find- antibodies that can target SARS-CoV-2. The rock weathering in soils has substantial techni- ings might generate, it is crucial to stress that, next steps will be to test individual antibod- cal and economic potential as a global strategy even under optimistic assumptions, enhanced ies and antibody cocktails in animal models, for removing atmospheric CO2. When crushed rock weathering will sequester only some of to determine whether they offer protection, basalt or other silicate material is added to the annual global carbon emissions from and then to assess their safety and effective- soil, it slowly dissolves and reacts with CO2 fossil-fuel use. Therefore, reducing these ness in human clinical trials. An accelerated to form carbonates. These either remain emissions should still be the top priority for path might narrow the time lag between anti- in the soil or move towards the oceans. The averting dangerous climate change. But, as body discovery and proof-of-concept trials authors argue that this method would enable Beerling et al. note, any approach is insuffi- 14 in humans to as little as five or six months . between 0.5 billion and 2 billion tonnes of CO2 cient alone, and should be considered as part The most recent prominent example to be removed from the atmosphere each year. of a portfolio of options. of immunotherapy for infectious disease This rate is similar to that of other land-based Several other land-based carbon-seques- relates to battling the Ebola virus. In con- approaches2, such as the accrual of organic tration techniques rely on soils. However, cert with vaccines and conventional, carbon in soil, carbon capture and sequestra- inorganic-carbon sequestration by rock small-molecule-drug trials, the development tion in geological formations, and the addition weathering is fundamentally different from of monoclonal-antibody therapies for Ebola of biochar (a carbon-rich material) to soil. organic-carbon sequestration. The latter relies has progressed rapidly. Cocktails of anti- Beerling and colleagues find that removing on photosynthesis by plants to remove CO2 bodies, beginning with one called ZMapp, atmospheric CO2 through enhanced from the atmosphere, and on soils to retain the that target a key Ebola viral protein called GP rock weathering would cost, on average, plant carbon, mostly in the form of microbial in two crucial regions of the protein, are con- US$160–190 per tonne of CO2 in the United remains. In the future, therefore, scientists tinuing to be developed15–17. This progress in States, Canada and Europe, and $55–120 per should pay closer attention to what they mean efforts to tackle Ebola gives hope for similar tonne of CO2 in China, India, Mexico, Indonesia by ‘carbon sequestration’ — is it inorganic or immunotherapy achievements in targeting and Brazil. Furthermore, the authors report organic? SARS-CoV-2. Pinto and colleagues’ work marks that China, the United States and India — the The sequestration of atmospheric CO2 a major step towards that much-anticipated, three largest emitters of CO2 from fossil-fuel through enhanced rock weathering shares and much-needed, success. use — have the highest potential for CO2 some of the principal appeal, but also the removal using this method. However, they also challenges, of organic-carbon sequestra- Gary R. Whittaker is in the Department of note that the application of silicate material to tion. The fact that crop production benefits Microbiology and Immunology, and in the soil (Fig. 1) requires careful assessment of the is certainly a key asset of both methods. In the 204 | Nature | Vol 583 | 9 July 2020 ©2020 Spri nger Nature Li mited. All rights reserved. ©2020 Spri nger Nature Li mited. All rights reserved. case of enhanced rock weathering, the added rock contains essential plant nutrients, such as calcium and magnesium, as well as potas- sium and micronutrients that promote crop production in several ways. We would go even further than the authors do, to claim that these nutrients are currently insufficiently supplied in agriculture. Increasing soil pH alone would substantially boost crop yields in many regions of the world, because it is possible that low pH constrains crop production on more than 200 mil- lion hectares of arable and orchard soils3. This area is equivalent to about 20% of the total extent of these soils (967 million hectares; see go.nature.com/31rcajd). Consequently, on a global scale, acidity is the most important soil constraint for agriculture4. However, there have been no detailed multi-regional analyses of the difference in crop yield between low-pH ILSA B KANTOLA ILSA and optimum-pH soils, and such investigations would benefit the study of synergies between Figure 1 | Application of silicate material to cropland. Beerling et al.1 demonstrate that enhanced rock carbon-sequestration methods. The proposed weathering, achieved by adding crushed basalt or other silicate material to soil, is an effective strategy for rock additions could conceivably mitigate the removing carbon dioxide from the atmosphere. low use and supply shortages of agricultural limestone in several regions5. Furthermore, yields even decrease, where incentives fail to production, and are centred around managing calcium improves root growth in acidic sub- persuade farmers, or where supply chains soils. Farmers must be fully behind such a surface soil6, with crucial knock-on effects break down. But scientists should not be global effort or it will fail. Scientists might through greater water uptake by plant roots. deterred from evaluating such technologies, need to recognize that climate-change miti- Co-deployment of enhanced rock and should instead accept that farmers need to gation is not a sufficient incentive on its own, weathering with other soil-based seques- be in the driving seat in adapting soil manage- and that benefits to crop growth will need to be tration approaches might both reduce ment to meet their specific site and crop-pro- prioritized, as will financial incentives.