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New research sheds lights on the huge carbon store in Canada's seabed

New research sheds lights on the huge carbon store in Canada's seabed
A seabed habitat on the ocean floor off the coast of Nova Scotia seen on the third dive of the NOAA Deep Connections 2019 expedition. Credit: NOAA Office of Ocean Exploration and Research

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

Oceans have absorbed more than 90% of the excess heat from global warming and at least 25% of global carbon dioxide (CO2) emissions. They also store vast amounts of carbon, locking it away from the atmosphere for hundreds to even thousands of years.

Coastal habitats such as mangroves, seagrass beds, saltmarshes and kelp forests have gained significant attention as natural climate solutions. In comparison, the sediments that line the seafloor have been generally ignored, even though they have been estimated to hold carbon stores considerably larger than that of trees and soils on land. A major contributing factor has been the lack of reliable, high-resolution maps of the seabed's carbon store.

We are part of a group of scientists who set out to address that problem, and our recent study 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 has already changed on an unprecedented scale and in the next five years, 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, due to the scale of the problem, every tool will be necessary.

Natural ecosystems act as a major buffer against climate change. Of all the pumped into our atmosphere, around 60% is absorbed by our lands and oceans. Damage to these ecosystems from human activities is, however, limiting their effectiveness, with 10 to 20% of global greenhouse gas emissions originating from habitat degradation.

Forests and wetlands are often targeted for protection and restoration to help in the fight against climate change 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 recognized for many years, but their ability to exacerbate or mitigate human-caused climate change has only more recently been considered.

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.

New research sheds lights on the huge carbon store in Canada's seabed
Photo of muddy mixed sediment in Halls Bay, Newfoundland in 1990. Credit: Natural Resources Canada

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 100 times that of all Canadian seagrass beds and saltmarshes combined, and around 60% of the carbon contained in the trees of all the forests in Canada.

Canada's carbon-rich seafloor

There is considerable variation in the amount of carbon stored in different parts of Canada's seabed. On the 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 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

There is increasing evidence that human activities are impacting seabed sediment carbon stocks. For example, a recent study 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 emitted as CO2.

Although there is significant uncertainty 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 , saltmarshes and are already included in Canada's marine conserved areas 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 manage or modify human activities 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, 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.

Provided by The Conversation

This article is republished from The Conversation under a Creative Commons license. Read the original article.The Conversation

Citation: New research sheds lights on the huge carbon store in Canada's seabed (2024, June 14) retrieved 24 July 2024 from
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