Published September 24, 2025
By Alana M. Carlson, Marine Geoengineering Campaigner at the Center for International Environmental Law
This is the third analysis in a multipart series exposing the threats and risks connected to geoengineering and why these technologies must not be considered effective climate action.
As the climate crisis escalates, so does the search for solutions. Geoengineering — large-scale technological intervention in Earth’s climate system — is increasingly entering mainstream discourse. But behind the undeliverable promises of cooling the planet and capturing carbon lies a dangerous reality: geoengineering could devastate biodiversity and disrupt ecosystems, while sidelining real climate action.
At a time when Earth’s biodiversity is under immense pressure from climate change, pollution, and habitat destruction, geoengineering risks accelerating ecosystem collapse and species extinction. If deployed at large scale, these highly speculative interventions in the Earth’s atmosphere, oceans, and land could fundamentally alter the delicate balance of Earth’s vital systems, severely compromising our ability to protect the biosphere and restore it to a state that better regulates climate conditions and provides vital ecosystem functions. By creating the illusion of a “plan B,” geoengineering also risks delaying crucial action to cut greenhouse gas emissions and implement real solutions to the climate crisis.
For these reasons, the UN Convention on Biological Diversity (CBD) had the foresight to take a series of precautionary decisions relating to geoengineering, including putting in place a de facto moratorium on deployment, with strict criteria for experiments, in 2010. The moratorium has been reaffirmed repeatedly — including most recently at the United Nations’ biodiversity conference in October 2024 (CBD COP16) — in response to concern about the growth in uncontrolled experiments.
The Biodiversity Impacts of Geoengineering Techniques
Biodiversity describes the richness of life that makes up ecosystems. Robust biodiversity is essential for healthy ecosystems and our well-being. It underpins important functions, like pollination and climate regulation, and enables Earth to remain in the relatively stable climate conditions that have allowed life to thrive and flourish. However, geoengineering experiments pose grave threats to this already fragile balance.
Central to understanding geoengineering — and its potential for seriously undermining biodiversity and human rights — is the scale at which it is proposed, both geographical and temporal, in order to have a climatically relevant impact. Solar geoengineering deployment is theorized and modelled on hundreds of years of continuous deployment and as a planetary-scale intervention, while certain ocean carbon dioxide removal (CDR) techniques are theorized as utilizing 10-20 percent of the ocean’s surface and operating for decades, if not centuries, and some land-based techniques are estimated to utilize twice the world’s currently cultivated land.
Below, we explore the risks that different geoengineering techniques pose to biodiversity.
Atmosphere-Based Geoengineering Could Trigger Global Ecological Disruptions
Solar radiation modification (SRM) technologies are highly speculative techniques that seek to artificially cool the planet without addressing the drivers of the climate crisis. Deployment of these technologies would introduce novel risks and damage to people and the planet. Among these risks is the possibility of termination shock (an abrupt rise in global temperatures as a result of discontinued SRM), which means that if we were to start using these techniques, we could never stop without risking catastrophic harm.
Stratospheric aerosol injection (SAI) and marine cloud brightening (MCB) are proposed SRM techniques that could dim the amount of sun that reaches Earth. If this occurred, it would likely have negative impacts on plant species across the planet, resulting in increased food insecurity. Additionally, these technologies would likely lead to uneven temperature changes, such as excess cooling in the tropics and warming in the poles. Such changes would cause temperature stress — much like that observed with climate change — that species would be unable to adapt to, leading to negative effects across ecosystems globally.
Further harms from SAI include changes in precipitation and damage to the ozone layer. SAI would slow down the global water cycle, likely causing up to a 2 percent decrease in mean precipitation, which would undermine food and water security everywhere. Some forms of SAI would likely weaken our ozone layer, thereby allowing more harmful UV rays to reach Earth and species that would be unable to quickly adapt to the increased radiation.
Marine microbubbles — an SRM technique that proposes using artificial substances to increase the longevity of bubbles left in the wake of ships — may cause localized light dimming, and like SAI and MCB, termination shock if stopped abruptly after a period of continuous large-scale deployment.
As solar geoengineering does not address the root causes of climate change, and at the same time introduces the risk of mitigation deterrence, it is likely that the preexisting crisis of ocean acidification would be exacerbated, resulting in direct harm to the base of marine food webs and communities that rely on marine species for their livelihoods.
Marine Carbon Dioxide Removal Threatens Ocean Ecosystems
Marine carbon dioxide removals aim to force the ocean to sequester even more carbon than it already does. If deployed, these unproven, energy-intensive approaches would introduce immense novel risks to our already strained marine ecosystems and likely severely harm biodiversity to the detriment of marine functions and human well-being.
Ocean alkalinity enhancement (OAE) technologies propose increasing the oceans’ uptake of CO2 by making marine waters more alkaline — either through the introduction of processed alkaline minerals or by processing seawater electrochemically to remove acid from it. Mineral OAE comes with a high mining cost, comparable to today’s global iron ore industry, which would degrade freshwater and terrestrial ecosystems. Mineral OAE proposals pose direct harm to marine life through the introduction of highly caustic alkaline materials or highly alkalinized water that can burn marine species. OAE may cause short-term shock effects associated with the introduction of high alkalinity, and may cause further, not yet understood long-term impacts on biodiversity as well. Electrochemical OAE would involve processing enormous volumes of seawater, harming marine life in the process, and creating vast quantities of acid waste that require treatment and disposal. It is a highly energy-intensive process that risks displacing renewable energy, better directed toward decarbonizing energy systems and providing energy access.
Ocean fertilization (introducing micro- and macronutrients to the ocean to encourage algae growth) risks disrupting the connectivity of marine ecosystems. Such disruptions would likely impede the ability of migratory species to move as needed and be a barrier to many species’ reproduction. These techniques risk creating toxic algal blooms that poison marine species. Oxygen depletion events that would lead to the suffocation of species may also occur. Ocean iron fertilization has already been shown to be ineffective, and deployment is prohibited internationally.
Artification upwelling (pumping cool, nutrient-rich deep-sea waters to the surface through thousands of pipes) may be done in tandem with ocean fertilization and risks bringing stored carbon up from the deep ocean, which may intensify ocean acidification. Additionally, like MCB and marine microbubble enhancement, seaweed cultivation technologies are likely to cause localized light dimming, which would disrupt the basis of food webs.
Seaweed cultivation is also proposed in combination with biomass sinking, where bales of plant matter would be dumped at the bottom of the ocean to increase marine carbon storage. In addition to seaweed, wood, and crop residues from land are also proposed for this purpose. These techniques disregard the fact that deep-sea life is delicate, largely unknown, and provides many vital ecosystem functions, including oxygen and nutrient cycling in the oceans. They risk physical harms caused by depositing bales of biomass on the ocean floor, as well as from bottom-up acidification, which would occur as a result of the biomass’s inevitable decay. Such harms would lead to negative impacts across food webs, harm marine biodiversity, and communities reliant on marine ecosystems for their livelihoods.
Land-Based Geoengineering Would Disrupt Ecosystems on a Massive Scale
Enhanced weathering (EW) is OAE’s terrestrial cousin. It would see ground alkaline materials spread over farmlands and fields to artificially increase CO2 uptake. Like OAE, to do at scale EW would require an enormous amount of mining comparable to today’s iron ore industry, and would lead to all of mining’s associated harms. This technique comes with uncertainties about the ecological toxicity impacts of spreading crushed, uncharacterized, or poorly characterized materials over land-based ecosystems and agricultural lands.
Biochar (storing carbon as charcoal spread over land) and bioenergy with carbon capture storage (BECCS) would come with high ecological costs. To implement these technologies at scale would require growing biomass plantations on more than twice the land currently cultivated. These plantations would cause a massive loss of biodiversity due to habitat and food loss, as well as increased exposure to and decreased resilience to diseases. Additionally, fertilizer production and use would have to be scaled up, exacerbating the harms associated with it.
Biochar would also introduce unique pollution risks. In addition to using biomass for biochar, so-called feedstocks for it can include crop and wood residues, manure, tires, plastics, municipal waste, and sewage — all of which come with unique toxicity risks. Toxins taken up by plants grown in biochar-amended soils may lead, over time, to the accumulation of deadly arsenic, cadmium, lead, and mercury in animals and humans. Humans and animals would also be exposed to these toxins as airborne pollutants.
Direct air capture (DAC) is a technology that seeks to absorb CO2 from the air through solvents or sorbents that carry not yet understood risks for biodiversity from their manufacturing. The installation of DAC plants would exacerbate ecosystem fragmentation and cause immense water stress wherever deployed. Capturing up to 1 percent of annual greenhouse gas emissions would require as much water as 144 countries consume domestically annually. DAC also introduces novel risks of CO2 leaks around the plants, which may lead to suffocation events or rapid water acidification. The technology is also highly energy-intensive and carries the same risks as electrochemical OAE in this respect. Furthermore, captured CO₂ from DAC is also used in enhanced oil recovery (EOR), which claims to store CO₂ while extracting more oil. Thus, DAC is used to falsely label EOR as “low carbon” despite the increased emissions at the injection site and its continued support of further fossil fuel production.
A Bad Bet for the Planet, a Bad Bet for People
The potential direct and indirect harms to biodiversity and ecosystem functions from geoengineering mean these technologies pose significant, unprecedented, never-before-seen risks to a wide range of human rights. The UN Human Rights Council’s Advisory Committee has warned that the deployment of geoengineering technologies has the potential to violate the human rights of “millions and perhaps billions of people,” with the greatest impact on Indigenous Peoples, rural communities, and fisherfolk. Among the many human rights that would be undermined due to harm to biodiversity are the rights to life, the rights of future generations, and the right to culture.
Untestable except through experimentation at a large scale, the true extent of social, economic, and cultural harms of geoengineering would likely become apparent only once deployed. The harms to biodiversity and human rights could create “sacrifice zones” that further entrench the fossil economy and its harms, as well as other preexisting inequalities at the expense of those most vulnerable to the climate crisis.
Precaution Over Speculation: What Should Policymakers Do?
The global response to geoengineering must be guided by precaution, environmental justice, and human rights. Geoengineering is neither insurance to “buy time” nor any form of supplement to mitigation. Instead of entertaining dangerous, highly speculative technologies, policymakers must prevent the normalization of geoengineering in climate policy and prioritize real climate solutions that protect and restore biodiversity, including a full, fair, funded, and fast phaseout of fossil fuels.
To prevent the risks of geoengineering and protect people and the planet, governments should:
- Implement and enforce the CBD’s de facto moratorium on geoengineering domestically and across international fora
- Support the development of strong precautionary regulatory controls under the London Convention/London Protocol to block harmful ocean-based geoengineering
- Ban all outdoor geoengineering experiments, preventing any immediate harm and deterring technology development
- Work toward a Solar Geoengineering Non-Use Agreement to prevent dangerous planetary-scale manipulations of sunlight
- Stop public support and funding for geoengineering technologies and deny patents
- Reject geoengineering in climate policies and carbon market mechanisms, preventing its use as a loophole to continue emitting greenhouse gases
- Protect biodiversity and ecosystem integrity by avoiding harmful interventions, minimizing unavoidable impacts, and restoring damaged ecosystems
- Uphold the inherent and collective rights of Indigenous Peoples and the rights of frontline communities, ensuring their lands are not turned into sacrifice zones for speculative geoengineering projects
- Urgently prioritize real solutions to the climate crisis through a fast, fair, funded, and full phaseout of fossil fuels
The Future We Choose
The climate crisis demands urgent action — but not reckless interventions that jeopardize biodiversity and human rights. Policymakers must resist the illusion of geoengineering and instead commit to proven rights-based solutions. A world free from fossil fuels, rooted in justice and ecological integrity, is possible — but only if we reject false solutions and embrace real climate action now.
Image Credit: Flickr-Joseph-King
2013 TAMU Applied Biodiversity Sciences Amazon Field School on the Tambopata River in the Peruvian Amazon


