What is blue carbon and why is it vital for mitigating Canada's carbon emissions?

Marlow Pellatt spent time on Vancouver Island, taking samples of soil from deep underground and wading through water to understand the biodiversity in the area.

To an onlooker, it may seem like he’s playing in mud, but he’s actually researching how important coastal ecosystems are in Canada’s fight against climate change.

Pellatt, a coastal ecologist with Parks Canada, led a team that was part of an international effort to study and preserve coastal systems this year. The joint initiative involves Canada, the U.S. and Mexico to study "blue carbon" -- the carbon stored in marine ecosystems.

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"About a decade ago, there was interest in how these natural systems interact in the carbon cycle and what value they may have in mitigating climate change," Pellatt told CTVNews.ca in a phone interview.

It’s widely known that plants absorb greenhouse gas (GHG) carbon dioxide as part of the photosynthesis process, creating food for the vegetation by combining sunlight and water.

What scientists wanted to understand was how coastal plants and the soil located in mangroves, tidal salt marshes and seagrass meadows absorbed carbon and how efficient these ecosystems were in doing so.

WHAT IS BLUE CARBON?

It is the term scientists and researchers use to describe the carbon captured and stored in coastal and marine ecosystems. All water-based ecosystems such as wetlands, bogs and lakes absorb carbon but at a slower rate than coastal systems.

Researchers have long understood that plants absorb carbon through photosynthesis, but they wanted to understand how to harness the carbon-capture powers of the natural world.

As Pellatt walks around Grice Bay, a popular launch point for visitors of the Pacific Rim National Park Reserve in British Columbia, he is focused on the plants and soil at his feet. The location chosen for the research is a tidal salt marsh with eelgrass on Vancouver Island.

"The work that we've started off with is focused on the tidal salt marshes, and the seagrass meadows mainly because those are the ones that we've got a good handle on their ability to store carbon," Pellatt said.

 

Canada has the longest coastline in the world, spanning 243,042 kilometres, including mainland and offshore island coasts. With such a vast coast, scientists believe there is so much more to understand about these valuable ecosystems.

By coining the term blue carbon and understanding how nature absorbs and stores CO2, scientists and governments can work towards using Canada’s coastal ecosystems to their advantage in the fight against climate change.

SO WHY IS THIS IMPORTANT?

Understanding how much carbon coastal ecosystems absorb and store carbon, helps Canadians understand how to play a role in preservation.

Canada is committed to reducing emissions by 40 to 45 per cent from 2005 levels by 2030. There is a further goal for Canada to achieve net-zero emissions by 2050.

The most recent data from 2020 shows Canada emitted 672 megatonnes of carbon dioxide into the atmosphere, a reduction from 738 megatonnes in 2019. To hit the current 2030 target, Canada needs to be between 296 megatonnes and 333 megatonnes of GHG emissions.

If the coastal ecosystems are destroyed by natural disasters or humans, the carbon buried underground is released into the atmosphere. The Blue Carbon Initiative, an organization focused on saving coastal marine habitats, estimates when these ecosystems are degraded or destroyed as much as 1.02 billion tonnes of CO2 are released annually around the world.

Not only is carbon released, the ecosystem no longer absorbs CO2 after destruction.

A research article published in Science Advances in June 2021 called 'Natural climate solutions for Canada' explains blue carbon ecosystems can mitigate the release of 1.7 million tonnes of CO2 by the year 2030, which is the equivalent to 3.4 million barrels of oil.

This is why the federal government has invested in a three-year, $1.59-million Blue Carbon Canada collaborative project, with a team of researchers and policy experts from Parks Canada and Fisheries and Oceans Canada, along with other conservation agencies. The research will help determine where the country’s blue carbon ecosystems exist, their mitigation capacity and how they adapt to climate change scenarios.

The research paper explains that when ecosystems are disturbed, they aren’t able to absorb as much carbon. When restoration is involved, the ecosystems will bounce back but are not as efficient.

This showcases to Canadians and governments that preserving coastal ecosystems is extremely valuable in aiding Canada to achieve its 2030 GHG emission targets.

"These systems serve as this important, natural barrier that protects often the cities and these communities, and that that we settled on,” Pellatt said. “It's really important to understand these carbon dynamics and the biodiversity aspects, especially when we have to respond and adapt to climate change."

Coastal ecosystems help support fishery industries by providing habitats for wildlife and act as a barricade to land from floods and storms.

WHAT SCIENTISTS UNCOVERED IN THE MUD

Ecosystems along coastal areas absorb carbon at a faster rate than forests, despite the total area being much smaller than Canada’s tree ecosystems. Part of the reason is the storage capacity of trees versus coastal plants.

Where trees store CO2 in leaves and underground to feed themselves, plants in tidal salt marshes or mangroves have the ability to store carbon for thousands of years in the sediment below, which remains in ecosystems for centuries.

Gail Chmura is a professor in the department of geography at McGill University who specializes in biogeography, paleo-ecology and wetland dynamics. For years, Chmura has studied the complex ecosystems within the Bay of Fundy along the coast of New Brunswick.

"The muddy water comes in, sits there a bit because it's a basin…and all the mud settles and the water drains," she says of the tide that comes into the Bay of Fundy. "We found in something like six years at one site, there was nearly a metre of mud that had collected, and that mud actually was trapping a lot of carbon."

In a review published in Ecology Society of America in January 2011 called 'A blueprint for blue carbon: toward an improved understanding of the role of vegetated coastal habitats in sequestering CO2,' researchers compiled studies on coastal ecosystems and outlined where blue carbon is stored around the world.

Underneath the top layer of plants, oyster shells and dead wood, CO2 can be located at the roots of seagrass. From samples deep inside the ground, researchers determined blue carbon is captured over the short term and stored over the long term.

In one instance in Portlligat, Spain, researchers found carbon deposits more than 10 metres thick and over 6,000 years old. Along Canada’s coasts, researchers are confident the findings are similar, showing carbon stored deep within the soil for thousands of years.

SALT VS FRESHWATER ECOSYSTEMS

Over the years, scientists have discovered that ecosystems exposed to saltwater absorb more carbon dioxide than freshwater wetlands. So why is that?

According to a report on the Environment and Climate Change Canada website, created by Chmura, wet conditions caused by regular flooding on coasts are a reason for the efficient capturing and storing of carbon.

"When you lose one of these ecosystems… the organic matter can decompose pretty rapidly,” Chmura said. "As opposed to when it's got saturated soil, you have very, very slow decomposition.”

If wetlands dry up, the plant matter starts to decompose releasing methane into the atmosphere along with CO2. Both GHG emissions are harmful, but the destruction of wetlands contributes to methane pollution which is 25 times more potent than carbon dioxide over a 100-year period, destroying ozone layers longer. Saltwater systems do not emit as much methane.

Although both natural ecosystems store GHG emissions and the preservation of both is needed, researchers have further questions about the coast.

Through their research in Grice Bay, Pellatt and his team found that northern coastal ecosystems have different carbon-storing capacities than those of the south.

“Most of the carbon is not stored in the plants, but it is stored in the sediment because of the way the plants grow,” Pellatt said. “If we think about the eelgrass in these northern systems, they tend to be smaller, their roots tend to be shallower in the sediments, and hence, they just don't have that ability to store as much carbon over the long term.”

B.C.’s eelgrass beds appear to store “considerably” less carbon than the global average for this ecosystem, but the province’s salt marshes are on par with the global scale.

Like previous research, Pellatt’s team determined that B.C.’s salt marshes capture and store more carbon per unit than the province’s boreal forest.

“When we understand what's in these salt marshes, eelgrass systems, peat systems and forests, all of this shows the value beyond resource value. It shows the value of keeping these systems intact,” Pellatt said.