Climate change is already fueling dangerous heat waves, raising sea levels and transforming the oceans. Even if countries meet their pledges to reduce the greenhouse gas emissions that are driving climate change, global warming will exceed what many ecosystems can safely handle.That reality has motivated scientists, governments and a growing number of startups to explore ways to remove carbon dioxide from the atmosphere or at least temporarily counter its effects.But these climate interventions come with risks – especially for the ocean, the world’s largest carbon sink, where carbon is absorbed and stored, and the foundation of global food security.AdvertisementAdvertisementAdvertisementAdvertisementOur team of researchers has spent decades studying the oceans and climate. In a new study, we analyzed how different types of climate interventions could affect marine ecosystems, for good or bad, and where more research is needed to understand the risks before anyone tries them on a large scale. We found that some strategies carry fewer risks than others, though none is free of consequences.What climate interventions look likeClimate interventions fall into two broad categories that work very differently.One is carbon dioxide removal, or CDR. It tackles the root cause of climate change by taking carbon dioxide out of the atmosphere.The ocean already absorbs nearly one-third of human-caused carbon emissions annually and has an enormous capacity to hold more carbon. Marine carbon dioxide removal techniques aim to increase that natural uptake by altering the ocean’s biology or chemistry.Some of the methods of climate interventions that affect the ocean, such as iron (Fe) fertilization. Vanessa van Heerden/Louisiana Sea GrantBiological carbon removal methods capture carbon through photosynthesis in plants or algae. Some methods, such as iron fertilization and seaweed cultivation, boost the growth of marine algae by giving them more nutrients. A fraction of the carbon they capture during growth can be stored in the ocean for hundreds of years, but much of it leaks back to the atmosphere once biomass decomposes.AdvertisementAdvertisementAdvertisementAdvertisementOther methods involve growing plants on land and sinking them in deep, low-oxygen waters where decomposition is slower, delaying the release of the carbon they contain. This is known as anoxic storage of terrestrial biomass.Another type of carbon dioxide removal doesn’t need biology to capture carbon. Ocean alkalinity enhancement chemically converts carbon dioxide in seawater into other forms of carbon, allowing the ocean to absorb more from the atmosphere. This works by adding large amounts of alkaline material, such as pulverized carbonate or silicate rocks like limestone or basalt, or electrochemicall …
