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Protecting and effectively managing oceans and seabeds is crucial in the fight against climate change.

Oceans have absorbed and . They also , locking it away from the atmosphere for hundreds to even thousands of years.

Coastal habitats such as and have gained significant attention as . In comparison, the sediments that line the seafloor have been generally ignored, even though they have been estimated to hold carbon stores . A major contributing factor has been the lack of reliable, high-resolution maps of the seabed's carbon store.

We are part of who set out to address that problem, and details the creation of the first high-resolution maps of carbon in Canada's seabed sediments.

These maps provide the first steps towards including climate change considerations in Canada's seabed conservation.

Nature as a buffer

Earth's climate and , the world's human population will likely have overshot the level of emissions that would limit global warming to 1.5 C.

The most significant action to prevent the worst effects of climate breakdown is to considerably reduce the burning of fossil fuels. But, .

Natural ecosystems act as a major buffer against climate change. Of all the carbon dioxide pumped into our atmosphere, around . Damage to these ecosystems from human activities is, however, limiting their effectiveness, with originating from habitat degradation.

Forests and wetlands are often targeted for because they hold large amounts of carbon within their trees and soils. The important role that seabed sediments play in the ocean's carbon cycle has been , but their ability to exacerbate or mitigate human-caused climate change .

Mapping seabed carbon

One of the first steps towards incorporating climate change mitigation in seabed management is to quantify and map this major carbon store.

In our new study, we compiled the best available data on the composition of seabed sediments across Canada and combined this with a wide range of environmental data within a machine learning predictive mapping process to create the first national map of organic carbon stocks in seabed sediments.

The resulting high resolution seabed carbon map covers 4.5 million square kilometers, which is nearly 80% of Canada's total marine area, or 90% of the seafloor area above 2,500 meters.

In total, the amount of carbon estimated to exist within the top 30 centimeters of seabed sediments across Canada is 10.9 billion tons. This is equivalent to approximately , and around .

Canada's carbon-rich seafloor

There is considerable variation in the amount of carbon stored in different parts of Canada's seabed. On the west coast in British Columbia, the muddy sediments at the bottom of fjords and inlets were estimated to contain particularly high levels of carbon, along with parts of the enclosed Salish Sea. This was contrasted by very low carbon in shallower areas offshore, where strong waves and currents frequently stir up the sediment leaving little carbon to accumulate.

On Canada's east coast, enclosed inlets and bays also contained the highest amount of carbon. However, a significant amount was also predicted to occur in the deep channels of the Gulf of St. Lawrence. In comparison, the Arctic seafloor generally contained lower levels of carbon, but relatively high carbon was predicted in sediments close to the Arctic coasts and in the northern parts of Baffin Bay near Greenland.

Future developments

that human activities are impacting seabed sediment carbon stocks. For example, estimated that global fishing activities using bottom trawls and dredges disturb huge amounts of seabed sediments and may cause a considerable amount of the carbon to be .

Although there is in the scale of these estimates, the maps produced here may provide opportunities to better research appropriate management strategies to limit the potential loss of carbon due to disturbance of the seafloor in Canada.

Habitats such as seagrass beds, saltmarshes and kelp forests are already included in the hope that by providing them protection, their carbon storage capacity will be maintained or enhanced. One option would be to include carbon-rich seafloor sediments within Canada's expanding marine conservation network for similar precautionary carbon protection. This would be a sensible low-risk strategy.

There may also be the potential to that disturb carbon-rich seabed areas. Using this map to gain an understanding of where these interactions occur could allow better targeting of research and management actions.

Overall, seabed sediments are one of the world's largest carbon stores. It is important to consider how to best manage them as part of our toolbox for slowing down runaway climate change.

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