Marine ecosystems, such as mangroves, whales, and phytoplankton, contain carbon and are part of the ocean's carbon cycle. This cycle involves the movement of carbon between the atmosphere, ocean, and living organisms. However, claims that protecting marine biodiversity can significantly limit climate change by removing large amounts of CO₂ from the atmosphere are being challenged by recent research. Studies suggest that even if marine life is restored or increased, it would only slightly improve the ocean's ability to absorb human-produced carbon emissions. Therefore, preserving marine biodiversity should be considered important in its own right, not just for its potential role in climate change mitigation. The ocean holds about 37,570 gigatons of carbon, with nearly all of it—99.98%—in non-living forms, primarily as dissolved inorganic carbon. Living marine organisms, including coastal "blue carbon" ecosystems like mangroves and seagrass beds, contain about 9.2 gigatons of carbon. Phytoplankton, microscopic marine plants, play a key role in the natural carbon cycle. Through photosynthesis, they absorb carbon dioxide from the atmosphere and contribute to the "biological pump," a process that transports carbon to deeper ocean layers. However, the ocean's ability to act as a carbon sink—absorbing excess CO₂ from human activities—is mainly driven by physical and chemical processes, not just biological ones. Since the start of the industrial era, the ocean has absorbed approximately 167 gigatons of carbon produced by human activities, mostly in dissolved form. In comparison, the loss of carbon in marine ecosystems due to human actions is estimated at just 0.57 gigatons. Restoring these ecosystems could enhance the ocean's carbon absorption capacity, but only by about 1% of current human-caused emissions. The impact of restoring whale populations or reducing fishing pressure is considered minimal in the context of the overall global carbon cycle. Marine ecosystems are essential for biodiversity, food security, and coastal protection. However, promoting their protection as the main solution to climate change could be misleading. While preserving marine environments is crucial for both ecological and human reasons, reducing CO₂ emissions remains the most effective way to address climate change. Efforts to protect the ocean should be valued for their own benefits, rather than primarily for their potential to combat global warming.