Wetlands are carbon capture kings
Sixty years ago when hunters banded together to save wetland habitats, they couldn’t have foreseen just how valuable their efforts would be.
Field & Game Australia (FGA) emerged in response to concerns about the future of the iconic Pacific black duck and brought hunters together to save the wetland habitats crucial to a healthy population.
Hunters volunteered to pay licence fees to fund the creation of the network of State Game Reserves, which continue to provide important habitat for not only ducks but all waterbirds.
According to researchers from the Deakin University School of Life and Environmental Sciences’ Blue Carbon Lab, Victoria’s wetlands provide another substantial benefit, locking away the annual emissions of 185 000 people, or roughly the population of Geelong.
The tally, which came to 3 million tons of CO2 each year, increases our understanding of how the environment helps to regulate greenhouse gas emissions.
Lead researcher Dr Paul Carnell said inland or non-tidal wetlands were an integral part of Australia’s carbon budget.
“While a lot more is known about how trees suck up and store carbon, freshwater wetlands can actually sequester 20 to 40 times more carbon than forests on dry land,” he said.
The key to wetlands’ success in carbon storage is the mixture of plant material and sediment in the soil, which contains little oxygen, and makes it hard for the carbon to be broken down and re-released into the atmosphere.
“Instead the carbon in this material is stored in the ground, that’s called carbon sequestration, and each year new material is added to the wetland’s overall carbon store,” Dr Carnell said.
“It’s the reverse process of digging up and burning coal or oil, here wetlands are taking that gas and putting it back into the ground.”
Victoria has about 530 000 ha of inland wetlands, which include marshes, peatlands, pools and lakes, making up about 2.33 per cent of the state’s land area.
As part of their study, which was funded by the Department of Environment, Land, Water and Planning, ecologists from the Blue Carbon Lab worked with Victoria’s 10 Catchment Management Authorities to take soil samples from more than 100 different wetlands across the state.
The soil was taken to a lab where it was dried, pulverised and put through a machine to analyse how much carbon it contained.
In total, the researchers estimated Victoria’s inland wetlands had a soil carbon stock of 68 million tons, worth about $6 billion under Australia’s most recent carbon price.
The study, published in the journal Global Change Biology, found Victoria’s alpine wetlands had the highest overall carbon stocks, while permanent freshwater sites like billabongs sequestered the most amount of carbon each year.
“Many of us already know that wetlands are great places to find birds, are important for fisheries and provide vital ecosystem services such as nutrient cycling, erosion control and flood mitigation. So this data shows they play a critical role in carbon storage too,” Dr Carnell said.
“On the flip side, this means disturbance and loss of wetlands has the potential to release significant quantities of CO2 back into the environment.”
Head of the Blue Carbon Lab, Associate Professor Peter Macreadie said the new study estimated that since European settlement, the loss of wetlands in Victoria had released up to 74 million tonnes of CO2 equivalents, equal to the emissions of 16 million cars over one year.
“Since European settlement we have lost more than a quarter of our non-tidal wetlands here in Victoria, mostly due to agricultural practices and development,” he said.
However, wetlands also have a dark side which offsets their capture and storage of carbon.
“These wetlands can be large sources of methane emissions. They’re effectively nature’s fart factories. So that’s something we’d like to be able to quantify further in future research too.”
In the meantime, Associate Professor Macreadie said it was critical Victoria properly protected and managed the inland wetlands it had left including using an existing pathway, money collected through carbon offsets.
“Right now, if you purchase a carbon offset for your flight to Sydney for example, that program will most likely plant a certain number of trees they estimate will grow to store the CO2 equivalent to your plane trip,” he said.
“But we know that wetlands are far more efficient at storing carbon than trees. Here in the Blue Carbon Lab, we’re collecting the information so that governments and carbon offset providers may one day be able to offset carbon emissions by restoring wetlands.“