The Risks of Geoengineering on Biodiversity

Published September 24, 2025

By Alana Carlson , Marine Geoengineering Campaigner at the Center for International Environmental Law

This is a shorter version of an analysis published on CIEL's website.

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. 

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.

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. 

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 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.

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.

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. 

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.

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.

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.

Read the full analysis on CIEL’s website here.