By Nicole Masters
It’s heartening to see the increasing awareness and dialogue around the role of land management, groundcover, and their influence upon climate. In particular, to finally see the decades of research by Mediterranean climate expert Millan M. Millan become unearthed by a new generation of systems thinkers.
Millan describes a "two-legged" perspective on climate with one leg representing land use and water cycles and the other including greenhouse gas effects and the prevailing CO2-centric view. “Water begets more water” poetically describes soil as a nurturing "womb" for rain and climate, while vegetation acts as a facilitating "midwife." Through these metaphors, Millan provides unique insights into the complex dynamics of our planet's climate.
Water affects climate from the micro to the macro. From the transpiration of water bodies (oceans, dams, and even ponds), local wind and humidity are influenced. On the macro scale water vapor is the most powerful greenhouse gas, accounting for around 97 % of the total global greenhouse warming. The primary reason for our moderate climate is the remarkable capacity of water to absorb solar radiation and heat. The water cycle involves an exchange of energy, resulting in temperature variations. As water evaporates, it undergoes a change in kinetic energy, which in turn cools down the surrounding environment. Conversely, when water condenses, it releases energy, thereby warming the environment. Let's delve into how this process works. When water transforms from a liquid state to vapor (evaporation), it produces a cooling effect, like the sensation we experience when sweating in a breeze. These mechanisms have a significant impact on the climate. Without water's role as a buffer in the atmosphere, global temperatures could potentially rise by 91°F (33°C). Despite the central role of water vapor in human-induced climate change, it has been largely overlooked by media, politicians, and climate scientists, who (incorrectly) assumed that human contributions to this phenomenon were insignificant.
Studies have demonstrated that bare exposed soils alter rainfall dynamics, with one Montanan study showing that chemical fallow practices (the practice of leaving fields naked to the elements), push the atmospheric boundary potentially 2600ft (800m) higher. Since the 1970’s a shift away from fallows in Canada has resulted in an increase in precipitation and a decrease in summer temperatures. Following the deforestation upon colonization in Australia, summer rains dropped by 12%. Across the Australian wheatbelt, winter rainfall, when crops need it the most, has declined by 19% in the past 50 years. Bare fallow practices have influenced the creation of a large barometric high over Western Australia. This, in part, pushes rains to the south and away from the wheatbelt. Millan posits that improving land management on as little as 25,000 ac is enough to alter precipitation dynamics.
Microbes too play a central role in water dynamics in soil and rainfall. Between 69-100% of precipitation contains ice-nucleating bacteria that seed clouds, from families which include Pseudomonadaceae, Enterobacteriaceae and Xanthomonadaceae as well as Lysinibacillus.
Samples collected from clouds found over 30,000 different species of bacteria and fungi; a quarter of the bacteria and most of the fungi collected were actively metabolizing. Generally, these species are found in the environment, living on, or in plants as symbionts, endophytes or pathogens. A type of rust, Puccinia lagenophorae, which ravaged wheat crops in the late 1920s, may possibly have had a role in altering climate dynamics, becoming one of the contributing factors to the 1930s dust bowl.
Deep, well aggregated, biologically active soils are THE central feature of a functioning water cycle. Imagine your microbes as power-packed tiny water bubbles. As biological biomass and predation increase, this water is released into the pore spaces. The water holding capacity in a soil is driven by several interrelated factors, not just soil organic matter, but porosity and structure, texture, and bulk density. New research also points to the role of microbiology in the formation of biogenic amorphous silica (bASi) in improving soil texture and water holding capacity. BASi can form silica gels with a water content at saturations higher than 700%, dramatically increasing plants’ resistance to drought. In agricultural soils, bASi pools have been reduced to levels of ~1% (or lower) contributing to a significant decrease in the soil’s water holding capacity. These forms of soil Si are disrupted by crop removal, haying, overgrazing, cultivation, deforestation, desertification, and anything which undermines decomposition and the return of plant materials to the soil.
The soil's biological exudates and decomposing organisms not only bind the particles together but also create space for water, which is essential for all life. When these processes work harmoniously, a beneficial feedback loop is established: the higher the carbon content in the soil, the greater its water-holding capacity. With more water in the soil, vegetation can thrive and flourish. As plants transpire, they release moisture into the atmosphere and draw more carbon into the soil, creating a virtuous cycle. This cycle brings more water, sequesters carbon, and remains hidden beneath the surface like the nurturing womb in Millan’s metaphors.
Through following the soil health principles, improvements in soil health lead to improved water dynamics. Water issues can be addressed by building the soil sponge, slowing and spreading the movement of water and keeping ground covered. Through maximizing photosynthesis to shade soils and stimulate microbial communities, increased sugars are drawn into the ground. Ever noticed how if you leave white sugar out on a bench, it will develop a crust on the surface? Sugar draws water molecules towards itself.
If soil is the womb, then it is the trees and green vegetation who are the midwives in the water cycle. A large tree may be drawing upwards of 150 gal (600 lt) per day through their roots and out through their leaves, with estimates pointing to the cooling power of 2 air conditioning units all day, every day.
A 2016 study by GOAmazon revealed that it is the interactions between forest biology, aerosols and clouds which keep the Amazon’s ecosystem functioning. These aerosols are formed by dusts, microbiology, and volatile organic carbons (VOC), such as terpene, isoprene, sesquiterpenes, released by the rainforest. Imagine these aerosols as tiny particles resembling seeds that are suspended in the air. They are called cloud condensation nuclei, which act as catalysts for the formation of cloud droplets by attracting water vapor to condense on them. These aerosols condense into minuscule particles that are carried upwards by the convection currents in the atmosphere, reaching heights of up to 49,000ft (15,000m). Within these convective clouds, strong downdrafts of air are created, resulting in the formation of precipitation such as rain. As a result, these particles descend towards the ground, effectively cleansing the atmosphere and initiating the next cycle of "aerosol embryos." These amazing VOCs travel high into the atmosphere before being redistributed around the planet very efficiently. Some of this outbreath from the Amazon heads to the Andes, while some goes to southern Brazil.
Soil biological systems and land management have largely been ignored in global climate modelling, overlooking the vital role well-managed soil systems play in mitigating greenhouse gases (GHG) and climate dynamics. Why are the biological water mediated processes in climate dysfunction being largely ignored? One argument is that these systems are too complex and variable to model, it’s not as easy to calculate inputs and outputs as it has been for many of the GHG models. Another may be that markets and political forces find monetization of carbon credits more profitable and simpler than investing in good land use management and native forest restorations.
Keeping ground covered, encouraging a diversity of plant species, enhancing microbiological function all play a key role in water and climate dynamics, on your own land, and beyond. Focusing on building vibrant diverse ecosystems has direct benefit to a rancher or farmer, beyond any potential ecosystem credit. I wonder, can you imagine what a revived water cycle looks like in your part of the world? And how far-reaching can the actions of a few be?
