Local Wetlands More Of A Climate Change Powerhouse Than The Amazon

Do sea level rises help save the planet? It’s a tricky question but in some instances rising sea levels do have a positive impact especially around natural coastal wetlands.

In fact, Australia’s coastal wetlands are carbon sequestration powerhouses according to research undertaken by the Blue Carbon Horizons team.

According to Professor Neil Saintilan from the Department of Earth and Environmental Sciences at Macquarie University, mangroves and saltmarshes are the world champions of carbon sequestration and “not the Amazon”.

Winners of the recent Eureka Prize for Environmental Research, the Blue Carbon team comprising researchers from Macquarie University, the University of Wollongong and ANSTO found wetlands are at the forefront of carbon storage.

Professor Saintilan says coastal wetlands are efficient natural systems in the trapping of carbon dioxide.

So how does it work?  Put simply, in wetland areas such as mangroves, the soil is saturated and has a high saline content which locks away the carbon in the roots.

Infographic: Wetlands store much of their carbon by burying sediments underwater, that are often loaded with organic, carbon-rich matter. When tidal wetlands flood from tides or sea-level rise, sediment accumulates above the bedrock floor. The higher the waters rise, the more space exists for sediment to build up.
Credit: University of Wollongong

As for the Amazon rainforest or any forest, they have a lot of carbon in the soil as well as oxygen and, carbon and oxygen don’t mix. The upshot is a lot of carbon is released back into the atmosphere.

Bearing this in mind, the rate of carbon capture in mangroves “is an order of magnitude higher than rainforests”.

And it’s not as though they’re all small little trees sitting on the fringe of waterways. In some areas of South America, the mangrove forests can grow as high as 63 metres tall – that’s a lot of carbon and it’s all being locked away in a secure, salty underground vault.

Unfortunately, we’ve managed to destroy many of our coastal wetlands globally for farming of livestock and in the case of our regional neighbours, the planting of palm oil plantations but we’re slowly beginning to reverse this destruction.

In the case of the Blue Horizons team, they discovered the capacity of coastal wetlands to store carbon will substantially increase with sea level rise.

Saintilan says this will offset some of the effects of global warming but it doesn’t mean we should all move to the hills and wait for the oceans to start lapping out our feet.

“It only provides a small negative feedback to global warming, it’s not the solution.”

What we need to do is to immediately start restoring our coastal wetlands which might include letting nature (or the tide) do its work in reclaiming low-lying land lost to farming.

Fellow member of the Blue Horizons team, Associate Professor Kerry-Lee Rogers from the University of Wollongong, said the team worked on a wider global project looking at the variability of carbon levels in saltmarshes.

Nothing could explain the variability until they started to look at the history of sea level rises over the last few thousand years. What they found was where the sea levels were rising the fastest in places such as the United States and Europe, there was more carbon sequestered.

In a place like Australia where sea levels have remained fairly stable for thousands of years, the carbon levels were constant. What they discovered is wetlands pump more carbon into their root systems as sea levels rise.

Now the Eureka moment came when an old mine on the NSW coast at Chain Valley Bay was shuttered in the 1980s.

As the old coal mine tunnels sank under the bay after many of the tunnel supports were removed, it simulated a sea level rise.

“What we saw was how Australia’s low carbon saltmarshes reacted to this sea level rise. The marshes grew quickly and the level of carbon also grew dramatically as it was sucked from the atmosphere and pumped into the root systems underground,” Associate Professor Rogers said.

Rogers reiterated the fact that our coastal wetlands and all of our natural coastal landscapes should be preserved as they are “and where we can restore them we should take up that opportunity.”

She said the federal government is working towards a mechanism for coastal wetlands to be included in the emissions reduction fund.

Professor Rogers also emphasised the need for development to be better planned in coastal areas as “we need to be smarter.”

“We should also think more about land clearance in other countries and take into account where we buy our produce from such as shellfish from Thailand or anything containing palm oil sourced from reclaimed wetlands in Indonesia for example,” she concluded.


Lead Image: Kerrylee Rogers from the University of Wollongong’s School of Earth, Atmospheric and Life Sciences, researching tidal saltmarsh in Tomago, New South Wales, Australia.
Photo Credit: University of Wollongong

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