What soil do you want to leave as your legacy?
WORDS BY PHILIP MULVEY
We are in the Anthropocene. The time when the main geological change agent is people. Each year we move more rock and earth than the forces of nature. We also alter the climate. We have anthropogenic climate change. But did you know we also alter soil that essentially link between the earth and climate (the atmosphere).
Most rural soil has been altered by people to be what it is now.
In the late 1980s, Dr Keith Helyar of the NSW Department of Agriculture realised that there was a connection that the soil developed under the Pilliga Forest in Western NSW, was due to the land practices of the Australian Aboriginal groups. The soil, which had an alkaline topsoil at odds with its parent material, could only have been created by intentional and prolonged management of fire.
Professor Gammage1 more than 20 years later, observed that nearly all of Australia’s savannah, woodlands and forest landscape and vegetative patterns were intentionally created by Aboriginal groups. Between 1836 and 1840 approximately 40 soil samples were collected on the east coast of Australia as part of a scientific investigation by Pawel Strzelecki2. He found soil organic carbon levels were between 5 and 12%, exceptionally high by today's standards. We now know that Aboriginal people have been using fire management of landscape to alter the soil over in excess of 10,000 years. The concept that the majority of savannah and woodland soil profiles have been created by human intervention is now gaining acceptance worldwide.
People, for a long time, have impacted soil at a landscape scale both positively and negatively (see images 1, 2 and 3). It is obvious that, if fire management by native people has impacted soil positively, the more invasive impact of soil disturbance through agriculture is likely to have a significant adverse impact. The archeological evidence shows this.
The Levant, the area in which agriculture first evolved in Europe and the Middle East (around the delta region of the Tigris and Euphrates, in Iraq and extending into Kuwait) has progressively changed from fertile cropping land, to grazing land, and finally, to desert3. This is the commonly understood pattern created by agriculture in semi–arid lands. But it only applies to environments in which annual evaporation exceeds precipitation.
Does agriculture in colder sub–temperate, higher latitude lands, in which annual precipitation exceeds evaporation, also suffer the fate of landscape degradation? Again the geological evidence from Mesolithic communities4 is that these lands were abandoned due to agriculture–caused landscape degradation, and have since become moors, peatland and marshes – not deserts.
Climate change caused by landscape change was first identified by Plato in Critias in 306 BC, in which he observed good soil husbandry produced an “attempered” climate. But poor management led to less rainfall, heavier rain events leading to more topsoil erosion, and more heat from the land. Strezlecki, in 18452, noted that land clearing, followed by degrading of soil through poor farming practices, reduced rainfall and increased heat from the land occurring faster in sandy soils. Both observed that agriculture changes the climate and leads to desertification.
Impacts in the UK, northern Europe and America by Mesolithic and Neolithic peoples practicing agriculture took longer to be recognised, due to the majority of land being moors, peats and marches, disguising the impact of people in causing these landscapes features. In these latitudes, agricultural degraded land leads to cooler, wetter conditions4, also unsuitable for growing crops and with time, unable to provide sustenance for stock.
In 1937, Carl Sauer5, sharply questioned humanity’s future in pursuing contemporary agricultural practices and observed that “humanity…had not yet learned the difference between yield and loot”. Modern agriculture's pursuit of yield has conflated the two. Unlike most businesses, agriculture is largely driven by yield and not profit stimulated by governments and research organisations funded by Big Farmer (agri–businesses). Reducing inputs seems not to matter to many agriculture researchers and advisors who have a vested interest in chasing yield. A “long” agriculture research experiment is 2 years and misses true sustainability assessment, which assesses profitability and environmental impacts over the long term (up to a decade).
In Australia it took less than 200 years to deplete soil organic matter (SOC), in soil by over 75%, leading to widespread soil erosion and landscape degradation, lower rainfall, hotter summers and increased floods6. We changed our soil and the landscape and climate responded.
In America it took less than 50 years for the tornadoes to follow man–made irrigation 150 miles westward into Kansas, which was accelerated post President Nixon as the windbreaks were removed and irrigation increased.
There are similar changes to climate as a result of soil and vegetation changes from Brazil (less soil organic matter, less rain) to Mongolia (less soil organic matter, increases in number and duration of cold snaps) and in the developed world from UK to Spain (less infiltration due to less organic matter leading to increased runoff, more flooding, as witnessed in the past few months, and more desertification).
There are two major anthropogenic climate forcing agents. One as we all know is gases emitted by our activities that collect in the atmosphere and reflect the heat we create back to earth. They are collectively known as greenhouses gases. The other as set above is degradation of our soil and landscape affecting how the earth’s surface responds to solar radiation that hits its surface
Soil covered with vegetation and rich in organic carbon converts nearly all the incoming solar radiation to evaporating or transpiring liquid water to vapour. Bare ground does not do this and the incoming solar radiation heats the ground which releases infra–red for the greenhouse gases to reflect back to earth. Degraded land is the heat source and the greenhouse gases are the blanket, a 2–step process, illustrated clearly below:
Addressing one without the other is not reversing climate change.
In 2011, the rate of human–led change in soil was so concerning to the soil science community that a committee was formed to communicate that “we must learn the difference between yield and loot in the coming decades and adjust our uses of soils accordingly”7. This is researcher language for “we need a new way of doing agriculture, and fast”. Polite, as you don’t want to upset funders, your peers or your employer (institutions and government).
In the last 6 years, I have continued my lifetime journey of repairing degraded land but this time focusing on the benefits from Regenerative Agriculture. During this time I have learnt that urine and manure patches and rock “floaters” are all indicators of degraded land. Recently, during filming of an upcoming series of videos on regenerative agriculture (www.timthompson.ag), I visited a number of farms, including two farms that had better indicators of soil health and a deeper soil moisture profile than that of undeveloped native forest nearby. One of which had worked out how to solve the rock “floater” problem. They started by identifying the rocks did not float up but the soil eroded away (see images 4, 5 and 6).
Image 4, 5 & 6: Using Stock grazing to remove Stone “Floaters” – Rock exposed during erosion of soil by poor practices. Soil goes down rather than rock goes up. Photos are a year apart from the same location.
.jpeg)
These farms maintained productive, more profitable farms than the traditional practices of their neighbours who often had a higher yield. The regenerative agriculture farms had vegetative cover of soil at all times, diverse species above and below the ground and incorporated grazing animals in their rotation system. Though they were not registered as organic, they did not apply any manufactured fertiliser, herbicides, fungicides or pesticides at all, for more than 10 years. At least one farm did not apply any fertiliser at all, relying solely on microbial fixed nitrogen and microbial release of stored phosphate and rotation of animals to fertilise the pasture.
How we farm, changes not only our soil for the better but our landscape and our climate resilience as well as our climate. In these farms it was not just soil health that had returned, so had both native fish and numerous species of small birds. The small water cycle had returned bringing more summer thunderstorms (known in Australia as square clouds – as they tend to only fall on regenerative farm and forested land) and mists and dews increased, leading to an increase in effective rain, and less frosts and less extreme heat days. In one instance runoff did not occur after a 150 mm (6”) two hour rainfall event onto what was a heavy clay soil (basalt parent material). Thus stream water quality has drastically improved and stream flow continues well into the summer.
The improvements to soil and climate health from regenerative practices in agriculture are more evident every day as more farmers are learning about effective land management strategies. It is clear that a decrease in vegetative cover and soil organic matter adversely changes our landscape and climate, potentially more so than greenhouse gases. In contrast, an increase in vegetative cover to 100% of the area, 100% of the time, increases our soil organic matter and not only causes positive changes to our landscape but also reverts the anthropogenic climate change restoring the small water cycle, providing an attempted climate and a climate resilient landscape. These changes can be achieved in a productive agriculture system. It is called Regenerative Agriculture.
Aggregated soil does more than we give it credit for. It is known that losing aggregation loses most soil functions and leads to landscape degradation, desertification and changes to climate. We now have early evidence that reversing degradation back to an organic matter rich, aggregated soil restores climate to its previous state.
Knowing this we ask, what soil do you want to leave as your legacy? Choose to practice, or insist on food and fibre from regenerative agriculture or continue with the status quo and chase “loot”.
References
The Environmental Earth Sciences International Group acknowledges the Traditional Custodians of country throughout Australia and their connections to land, sea and community. We pay our respect to their Elders past, present and emerging and extend that respect to all Aboriginal and Torres Strait Islander peoples today.
.png)
