VICTORIA'S TEAL CARBON
Nontidal wetlands are estimated to contribute significantly to the soil carbon pool across the globe. However, our understanding of the occurrence and variability of carbon storage between wetland types and across regions represents a major impediment to the ability of nations to include wetlands in greenhouse gas inventories and carbon offset initiatives.
We performed a large-scale survey of nontidal wetland soil carbon stocks and accretion rates from the state of Victoria in southeastern Australia—a region spanning 237,000 km2 and containing >35,000 temperate, alpine, and semi-arid wetlands.
Our specific objectives were to: (a) Undertake a landscape-scale assessment of wetland soil carbon stocks by sampling wetland soil carbon from more than 100 wetlands spread across Victoria; (b) compare carbon stocks between wetland types and assess regional variability; (c) Utilize existing data on wetland soil accretion rates, combined with newly collected soil carbon data to estimate wetland soil carbon sequestration; and (d) based on this data, estimate soil carbon stocks and sequestration capacity for the entire region and the potential impact of historical wetland loss on carbon emissions from wetlands.
Global estimates suggest that freshwater wetlands contain 20%–30% of the terrestrial soil carbon pool, a disproportionately high contribution given that they occupy just 7% of the land surface. Despite their importance, freshwater wetlands have been historically underappreciated, with 87% of global wetland being lost since the early 1700s. They are threatened by land-use change, pollution, water extraction, and landscape modification. Quantifying the contribution of wetland ecosystems to carbon capture and storage is vital to justify the application of improved management strategies that ensure their continued contribution to a
multitude of other ecosystem services.
Carnell PE, Windecker SM, Brenker M, Baldock J, Maque P, Brunt K, Macreadie PI (2018)
Global Change Biology 24: 4173-4184
From an analysis of >1,600 samples across 103 wetlands, we found that alpine wetlands had the highest carbon stocks (290 180 Mg Corg ha1), while permanent open freshwater wetlands and saline wetlands had the lowest carbon stocks. Permanent open freshwater sites sequestered on average three times more carbon per year over the last century than shallow freshwater marshes. The duration of water inundation, plant community composition, and allochthonous carbon inputs likely play an important role in influencing variation in carbon storage.
We estimate that wetlands in Victoria have a soil carbon stock in the upper 1 m of 68 million tons of Corg, with an annual soil carbon sequestration rate of 3 million tons of CO2 eq.year1—equivalent to the annual emissions of about 3% of the state’s population.
This work was led by Dr Paul Carnell from Deakin University’s Blue Carbon Lab, involving partners from Edith Cowan University and the Victorian Catchment Management Authorities (CMAs): North Central CMA, North East CMA, Goulbum Broken CMA, Glenelg Hopkins CMA.
Funding was provided by Victoria Government’s Department of Environment, Land, Water & Planning grant (DELWP) and an Australian Research Council Linkage grant.