BUILDING soil carbon stocks to reduce emissions has taken a step forward with 25 countries, including Australia, agreeing to increase soil carbon at the Paris Climate Conference.
The initiative recognises that soil can act as a sink for greenhouse gas emissions.
The agreement is referred to as “4/1000,” and is a voluntary pledge to reach a 0.4 per cent annual growth rate in soil carbon content.
In Australia, this would equate to sequestering an average of 0.22 tonnes of carbon per hectare according to the University of Sydney.
The objective of the Paris climate talks - also known as COP21 - to reach a universal agreement on climate was achieved in a landmark resolution with almost 200 countries agreeing to aim to keep global warming below 1.5 degrees C.
The 4/1000 initiative was launched by the French government as one measure to help reach the target and brings together contributors from government, business, NGOs and researchers.
Signatories to 4/1000 are expected to implement programs or policy of soil carbon sequestration which can be achieved by various means - ecology, forestry conservation agriculture or land management.
According to Sydney University the top two metres of soil holds four times the amount of carbon than is stored in plant biomass. Soil has the potential to store carbon for a very long time by various protective mechanisms.
However, land has progressively moved from a carbon sink to a carbon source as traditional tillage methods exposed soil to the air which causes carbon to oxidise to CO2.
Correctly managed soil is a carbon sink as plants draw down atmospheric carbon and convert it via photosynthesis to compounds including sugars which feed soil microorganisms.
The Faculty of Agriculture and Environment at the University of Sydney, said the target was ambitious but achievable.
Faculty spokesman, Budiman Minasny, said it meant “annually we need to sequester an average of 0.22 tonnes of carbon per hectare. This value falls between the estimation of sequestration rates of 0.19 to 0.3 tonnes of carbon per hectare per year, for best management practices in Australia where water is not severely limiting".
“The '4 per 1000' is an ambitious aspiration, however it is for the first time setting a global goal to promote good soil management that can help mitigate climate change,” he said.
“To achieve this we need disruptive technologies that can help agricultural practices to soak up more carbon in the soil, create soil security to achieve food security and mitigate climate change. Australia should be part of it.”
The 0.4 per cent annual growth rate of the soil carbon stock would make it possible to stop the present increase in atmospheric CO2 but is not seen as a “normative target for every country” as building soil carbon levels depends on a range of variabilities including temperature, rainfall soil type and types of organic matter.
The goal shows that even a small increase in the soil carbon stock is crucial to improving soil fertility and agricultural production and can help limit the global temperature increase to the target +1.5 per cent from pre-industrial levels.
This initiative is intended to complement other efforts to reduce global greenhouse gas emissions.
