Phil Mulvey, a specialist in soil and water chemistry, and his daughter, Freya Mulvey, a lawyer and science communicator, have challenged the climate science orthodoxy, arguing that climate change is fundamentally a heat and landscape management problem, not just an emissions problem. Of particular importance to forest managers is the revelation that soil degradation and land-use change are major—possibly dominant—drivers of climate change.
Their findings are detailed in “Ground Breaking: Soil Security and Climate Change” and build on the 2019 scientific discussion paper “Soil Security for Australia,” which set the scene for an Australian Soil Security framework defining the key issues and the justification for Soil Security. Mulvey’s book positions soil as a critical climate system, noting that soil stores both carbon and water; the transfer of heat to and from the atmosphere is influenced by vegetation cover (and the type of vegetation), and degraded soils amplify heat and reduce rainfall.
After co-authoring the book, Freya was awarded a Churchill Fellowship to examine soil projects in countries that place greater emphasis on soil condition and the relationship between climate change and soil quality. The long-term aim is to implement best-practice soil and landscape regulation into Australia’s legal and policy frameworks.
Phil says that, “Those who seek to lock up native forests and leave them to preserve the carbon sequestration in the timber are ignoring the greater carbon sink potential of the soil from which the forests grow and the loss of forest (carbon sink which they rely upon) to fire — directly as a result of no management.”
Soil organic matter (carbon) content is often linked to soil fertility. Woodlands and managed thinned forests with shrub and grass understorey develop an organic layer not only above, but also penetrating into the regolith (this is everything above the unweathered rock). This layer generally improves soil aeration, water infiltration and retention, and builds up soil microorganisms, which enhance soil quality.
Interestingly, Phil said, “Aboriginal management had less dense forests approaching woodlands as outlined in Mariani et al. 2022 and grasses mob-grazed by marsupials, which increased soil organic matter and would potentially offset lower litter inputs compared with those of unmanaged, denser forests.”
“Recent fires have shown that fire stops at soil with deep topsoil, which increases the relative humidity in the air above the soil, reducing flammability and stopping the ingress of fire.”
“Biologically active soil stimulated by the combination of grasses and trees reduces dried litter (fuel load). This factor, together with regular cultural burn patterns, ensured that fires lit by Aboriginals were contained in woodlands even during extended drought, as observed by the explorer Sturt in the 1826-1828 expedition.”
Mulvey’s experience has found that the Aboriginal people built up a healthy soil profile not just through leaf litter. Soil fungi have a significant role in healthy soils. The roots of grasses and trees play a role in the growth of fungi. There is a cooperative role among these roots that aggregates the soil and brings minerals to the trees. When you get too many trees, you do not get the system that allows this process. You need the grasses. Flowering grasses and flowering trees developed together. These were not common in the dinosaur period and co-developed after the meteorite fall. They also co-developed with animals that kept the areas open. Australian Indigenous people, through cultural burning patterns, effectively copied this system.
Based on Phil’s observations and comments, our national parks and state forests generally lack the benefit of deep, organic-matter-rich soils because they have a thick upper storey rather than a less dense canopy with a grass understory. Without deep, organic-matter-rich soils, there is less water content and a drier atmosphere above the ground. This makes them prone to destructive wildfires.
People serious about maximising carbon sequestration in Australian native forests, based on Phil’s comments, need to recognise the value of soil sequestration in native forests that are managed, and the importance of the whole ecosystem above and below ground.
Editor’s note: This is an opinion article. Wood Central does not take an editorial stance on the Australian native forest debate and runs contributions from across the sector. Direct extracts from the IPCC SRES Land Use chapter, and the IPCC Special Report on Climate Change and Land are reproduced verbatim with links.
