Natural carbon sinks are weakening, and if they fail, it will trigger runaway climate change from which we will not be able to recover. Nature’s carbon sponges cannot keep pace with the massive amount of carbon (CO₂) being generated by our fossil-fuel-intensive economies. The Earth’s carbon cycling capacity is faltering, and if the planet stops buffering our emissions, there is no hope of staving off the worst impacts of climate change. Natural carbon sinks absorb half the emissions humans generate each year. Without them, atmospheric emissions will rise dramatically and push the planet toward irreversible collapse. A carbon sink is any system that absorbs and stores more carbon dioxide from the atmosphere than it releases. Examples of natural carbon sinks include oceans, forests, and soils. Their ability to sequester carbon is what keeps our planet from getting unsustainably hot. Carbon sinks cool the planet by reducing the concentration of global-warming-causing greenhouse gases (primarily CO₂) in the atmosphere. However, nature’s capacity is not infinite. A carbon sink can become a source of carbon. The three biggest natural carbon sinks are oceans, forests, and soil. Oceans hold 38,000 gigatons (Gt) of CO₂ that they absorb through chemical, physical, and biological processes (e.g., phytoplankton). Forests store 870 Gt of CO₂. Trees and plants absorb CO₂ during photosynthesis, storing it in trunks, roots, and soil. The top 3 feet of soil contain 1,700 Gt of carbon, which is more than twice the amount of CO₂ emitted by fossil fuels since the dawn of the industrial revolution. Soil absorbs CO₂ primarily through a process called soil carbon sequestration, which stores carbon in organic matter (SOM), composed of dead plant matter and microbes. The amount of carbon in the soil is decreasing, and losing its capacity to store carbon. Soils are storing less CO₂ due to global warming, intensive farming, and agricultural conversion. Deforestation releases carbon from the soil, and it also eliminates the carbon sequestering capacity of the trees and vegetation that are removed. Some forests are switching from carbon sinks to net emitters of CO₂. A 2023 paper found that parts of the Amazon rainforest became net carbon emitters. This is the case in Australia’s tropical rainforest, where extreme temperatures and drier conditions have resulted in more dead trees and less tree growth. Another 2025 study found that Africa’s forests may have also hit a tipping point, transitioning from carbon sink to carbon emitter. Earlier studies indicate that parts of the Amazon rainforest are also emitting more carbon than they are sequestering The oceans are by far the Earth’s largest carbon sink, and they are losing their ability to store CO₂. A 2025 study indicates that some parts of the ocean (e.g., tropical seas) have switched from sinks to sources of carbon. The weakening of the ocean’s biological carbon pump is disrupting the movement of CO₂ from the surface to the deep sea. This weakening is primarily due to global warming, which disrupts the natural physical and biological “conveyor belt” that transports carbon from the sunlit surface to the deep sea. Warming is also contributing to phytoplankton declines, which significantly decreases the ocean’s CO₂ absorbing capacity. This observation was corroborated by a 2025 study that found the oceans have less chlorophyll, which is associated with a lowered carbon sequestration capacity. The temperature-stabilizing capacity of natural carbon sinks is in jeopardy, and anthropogenic emissions keep increasing. If oceans, forests, and soils, stop absorbing carbon, the climate system will shift from self-regulating to self-amplifying. As natural carbon sinks lose their capacity to mitigate climate change, warming will dramatically accelerate. Warming of this magnitude risks triggering irreversible climate tipping points and ecosystem collapse. This will cause widespread disruption to food systems and water supplies. The weakening of natural carbon sinks is a threat to all life on Earth as well as human civilization. While human efforts like conserving forests, sustainable farming, restoring wetlands, and supporting kelp forests can increase nature’s capacity to absorb carbon, these efforts are not coming remotely close to keeping pace with the emissions emanating from our fossil-fuel-powered economies. Without these natural buffers, emissions cuts, no matter how large, will not be enough. These sinks are Earth’s last line of defense, and if they fail, the climate crisis will escalate from dangerous to unavoidably catastrophic. |
Wednesday, 4 February 2026
Weakening Natural Carbon Sinks Are a Climate Clarion Call
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