(This piece is an excerpt from observations by Peter Donovan of the Soil Carbon Coalition on a series of talks by Walter Jehne, founder of Healthy Soils Australia .) Our current method of agriculture and land management is largely monoculture, reliant on chemical fertilizers and pesticides, the plowing up the natural biome community in the soil, and expansion through deforestation, with little attention to how the natural world actually works. This piece takes a different perspective, another way that is more in line with Nature’s way and might be the solution to land degradation, drought, flooding, malnutrition/famine, and global warming.
The condition of the soil surface, and what’s growing on it, controls the fate of rainfall.
Deforestation, fire, and agriculture have tended to move landscapes leftward, baring soil, increasing fine dust particles that nucleate haze but not rain, planting short-season annuals, shortening the length of green season and the sugary plant root exudates that feed soil porosity and aggregation. Bare soil heats up, radiates, and some of this heat is re-radiated back from greenhouse gases. Regular fire or tillage bares soil and prevents the soil carbon sponge from developing. High-pressure domes over large expanses of hot bare ground repel rain. These landscapes multiply heat and aridity.
On the right, the formation of high-albedo rain clouds from abundant transpiration with bacterial precipitation nuclei helps recycle water locally, while the pressure drop from large-scale condensation drives the biotic pump, which brings in moist air from the oceans. When the clouds clear, heat can escape. Abundant plants harvest atmospheric moisture as dew. More solar energy is dissipated upwards by transpiration, and less by sensible heat. These landscapes multiply rainfall and cooling.
The soil carbon sponge may increase your local multiplier for rainfall–the number of times that water is recycled from soil to sky and back again before it leaves your area, either as vapor or runoff. If you are in a dry area, increasing your multiplier can be significant!
To shift a landscape to the right, keep in mind the soil health principles: integrate livestock, cover the soil, diversity, living roots as long as possible, minimize tillage. There is some evidence that a reduction in summer fallow (from 77 million to 20 million acres in the northern plains of the U.S.), and an increase in summer plant cover may decrease temperatures and allow for more convective precipitation.
The vast majority of the heat balance in our blue planet, Walter noted, is governed by water. Australian agricultural pioneer Peter Andrews wrote, “Plants manage water, and in managing water, they manage heat.”
The opportunity to cool our planet, Walter emphasized, is by influencing the hydrological cooling processes, for which plants and the soil carbon sponge are critical. He suggested that a small increase in high-albedo convective cloudiness might even be enough, and if the soil carbon sponge could be increased rapidly, cooling could be correspondingly rapid.
Walter noted that nature has been doing all of this since plants and fungi colonized the bare rock of land masses hundreds of millions of years ago. “We can lift our boot off nature’s throat.”
This is why we at Canillas Community garden encourage minimal tilling of the soil, cover crops, chop-and-drop, mulching, and why we prohibit pesticides. Thanks to Lebanon Public Works, we have shredded, un-sprayed leaves from Colburn Park to cover any bare soil throughout the winter.