Global decarbonization efforts have overwhelmingly focused on the energy and oil and gas sectors - and rightfully so, as electricity and heating are the top-emitting sectors. As such, developing renewable energy sources to support a sustainable transition of industries has taken precedence. Even with complete emissions avoidance and reduction, we would still face a climate crisis due to unavoidable emissions and legacy greenhouse gases.
‘Hard to abate’ emissions are attached to every activity and industry, and cannot, even under best-case assumptions, be eliminated. There are also legacy emissions – excess amounts of greenhouse gas we’ve been spewing into the atmosphere for over two centuries – which, even if we stopped completely today, will continue driving us down a dangerous environmental path.
Without actively removing emissions from the atmosphere, we will be unable to stop climate change, let alone reverse its impacts.
Carbon markets play a key role in our ability to measure and implement carbon avoidance, reduction, and removal strategies. However, recent analyses, including insights from McKinsey, suggest that the supply of durable carbon removals could be up to ten times lower than what is required to meet the IPCC’s 1.5-degree target. This stark gap highlights the urgency to expand our approach.
Active removal and reduction strategies have almost exclusively focused on land-based solutions, including engineered (i.e., Direct Air Capture) and nature-based approaches (i.e., reforestation). But an overlooked carbon sink holds enormous potential: water.
Water bodies have always played a key role in moderating the climate, naturally absorbing excess CO₂ through gas exchange with the atmosphere. Once CO₂ is in the water, phytoplankton utilize it for photosynthesis, generating oxygen and energy. Research estimates that phytoplankton, whether ocean or freshwater, provide 50% - and possibly up to 80% - of the world's oxygen, far more than all the trees on Earth, even though they make up less than 1% of the total green plant material on Earth.
Putting the ocean aside, freshwater ecosystems – our lakes, rivers, and wetlands – remain an underutilized asset in global climate strategies. Freshwater ecosystems have immense carbon sequestration potential, but neglecting their health risks turns them into major greenhouse gas emitters. Unfortunately, these freshwater systems - bursting with carbon sequestration potential - are under-researched and underfunded.
This oversight is more than a missed opportunity; it’s an active risk. By failing to safeguard freshwater health, we accelerate the climate crisis, jeopardizing not just biodiversity but global food security, economic stability, and public health.
Despite making up only a tiny fraction of the planet’s total water, freshwater ecosystems are among the most powerful players in the global carbon equation. Per unit area, they sequester and remove carbon at an unparalleled rate, predominantly through the first photosynthetic organisms to appear on Earth: cyanobacteria.
Cyanobacteria are the most efficient photosynthetic organisms, responsible for generating oxygen and sequestering carbon. When part of a balanced ecosystem, they create conditions that make freshwater lakes a net carbon sink. However, when out of balance, cyanobacteria can proliferate out of control, drastically shifting the biodiversity equilibrium, while deteriorating water quality to dangerous levels.
Cyanobacteria, the efficient photosynthesizers that make water such an effective carbon sink, are a double-edged sword. The same microorganism that allows water to act as an efficient carbon sink can cause it to become a significant emissions source.
This is the situation we face today. Excess nutrients, including phosphorus and nitrogen, combined with CO₂ saturation in the air and rising temperatures due to global warming, have created the perfect storm. These factors have collided, leading to an explosion of harmful algal blooms (HABs) in freshwater ecosystems.
Cyanobacteria HABs (aka: blue-green algae) are bacterial infections in water. Like an unchecked infection in the human body, HABs proliferate in freshwater bodies, destroying biodiversity, depleting oxygen levels in water and limiting water’s carbon sequestration potential.
Recent research has found that HABs also emit methane and nitrous oxide, potent greenhouse gases with far greater warming potential than carbon dioxide. In short, HABs disrupt ecosystem balance, preventing water from absorbing atmospheric CO₂, while also emitting greenhouse gases, further intensifying the problem.
To break this cycle, we need a new approach to carbon sequestration, one that prioritizes water health. Utilizing new monitoring technologies, researchers and environmental administrations responsible for water maintenance can track water quality and health in near real-time and identify problems (i.e., HAB outbreaks) early. The ability to assess the severity, size and specific location of HABs enables us to develop targeted treatment protocols and manage water health proactively instead of reactively.
Having reliable data also allows researchers to develop robust measurement methodologies to calculate the emissions removal impacts of HAB treatments. These approaches must be validated and regulated at the highest level.
Remediating HABs allows us to leverage the power of nature – cyanobacteria’s highly efficient photosynthesis capabilities – to rapidly remove active emissions and unleash freshwater’s full capacity as a carbon sink.
As the McKinsey research highlights, current methods alone won’t close the critical gap in durable carbon removals needed by 2030. To bridge this divide, we must expand our understanding of carbon sequestration to incorporate freshwater. This means embracing new technologies and investing in multidisciplinary research that accounts for the complexity of freshwater dynamics.
By improving how we measure, verify, and model carbon sequestration in lakes, rivers, and wetlands, we can reshape climate policies to reflect their true potential. Taking a collaborative approach and gathering stakeholders from policy, academia, innovation and investment will allow us to forge new pathways for funding, research and implementation of solutions.
This will allow freshwater to take its place in global carbon removal efforts, enhancing the resilience of our climate action plans and helping us surpass emissions reduction targets for a more sustainable future.
Eyal Harel is an entrepreneur with a strong passion for protecting natural resources and improving global water quality. As the Co-Founder and CEO of BlueGreen Water Technologies, Eyal has developed new businesses and identified key market opportunities with the ultimate goal of making the environment safer for the next generation.
