A recent article ‘A warming climate will make Australian soil a net emitter of atmospheric CO2’, published in Nature Portfolio Journal said that predicted net losses of organic carbon from soil will significantly affect Australia’s ability to achieve its GHG emissions reduction target.
It also found that warmer and drier conditions will lead to more significant carbon loss in the rangelands than elsewhere in Australia.
On the surface it’s a gloomy outlook but if you dig a little deeper (pardon the pun) it also highlights the opportunity for better land management to mitigate the losses.
Senior remote sensing scientist at Cibo Labs, Dr Juan Pablo Guerschman is working on the Food Agility Rangelands Carbon project, a partnership with Australian Agricultural Company, Cibo Labs, FLINTpro, CarbonLink, University of Technology Sydney, Federation University and Charles Sturt University.
Dr Guerschman explains that rangelands account for more than 75 per cent of Australia’s land mass, and the sheer scale makes them important for soil carbon.
“Rangelands naturally tend to have low levels of carbon in their soils but because the total area is so large, even if there are small increases in soil carbon per hectare, the potential amount of carbon to be removed from the atmosphere and stored is quite big.”
The opposite is also true - a small decrease in soil carbon per hectare over a large area can have a big impact on Australia’s total carbon stocks.
Dr Guerschman said the modelling showing rangelands as net carbon emitters in the future assumes that there’s no change in management of the rangelands.
“They assume business as usual management but because it's slowly getting hotter there’ll be increased decomposition of carbon in the soil so that's why the rangelands are net emitters of carbon in that model,” he said.
“That also means that the opportunities for preventing that carbon from being released by improving the way the land is managed are huge.”
In a country as diverse as Australia, both in terms of farming systems and landscapes, there are challenges in measuring and understanding changes in soil carbon over time, and how that’s impacted by things like grazing management.
There’s also been criticism of how credits are awarded for soil carbon sequestration under the Australian carbon credit unit scheme (ACCU).
Dr. Guerschman emphasised that projects like our Rangelands Carbon project are critical to providing concrete evidence and scientifically robust data through intensive soil sampling and analysis to understand landscape carbon.
“The science has to be strong and that means intensive sampling so that the statistics and modelling applied to it are robust and supported by evidence,” he said.
The project team has undertaken intensive soil sampling over the landscape, with 1650 soil cores collected in 484 sites in 2022 and 2023. Drone images taken in 19 of those sites are being combined with satellite imagery to track vegetation changes over time.
“Samples have been taken in different landscapes, different types of vegetation, places with more grasses, less grasses, more trees and less trees and so on. We’ve also been targeting areas with evidence of different long-term land management and history,” Dr Guerschman said.
“We go and measure how much carbon we see in those places, where the landscape is a bit more degraded and places where it's less degraded in better condition. One of the most interesting things we are seeing is statistical evidence of higher carbon levels in soils in areas where the landscape is healthy.
“That is quite strong evidence to say, if we go to places that are not in the best shape, and we implement changes there and improve them then over time those soils will end up with more carbon.”
Read more about the Rangelands Carbon project on our website.
