Great civilizations of the past, such as the Sumerian Empire, Egypt, the Roman Empire, the Khmer-Angkor Empire, and the Maya of the Yucatan, ultimately fell due to their agricultural practices depleting soil organic matter and natural vegetation. This depletion led to vapor pressure deficits, causing prolonged droughts, torrential flooding rains, forest fires, and crop failures.
These civilizations collapsed because they were unable to feed their people and armies.
In regions like North Africa and the Middle East, the once-fertile fields have never recovered from human-induced environmental degradation and, thousands of years later, still remain deserts. In contrast, areas such as the Khmer territories in Southeast Asia and the Mayan Yucatán Peninsula have been allowed to regenerate and restore their climate naturally.
Just as each civilization failed to learn from the lessons of those that came before and instead repeated destructive practices, we are now witnessing this happening on a much larger global scale.
The world is experiencing an increase in extreme weather events, leading to reduced yields and more crop failures. Various regenerative agricultural practices can enhance the local climate, reversing climate extremes and restoring balance.
Vapor Pressure Deficit (VPD)
Vapor pressure deficits (VPD) worsen droughts and lead to intense rainfall when the drought ends, as the rising temperatures enhance moisture absorption from the vegetation and soil into the atmosphere. They drain the soil and vegetation of moisture, making the landscape more vulnerable to fires.
The total amount of water vapor that air can hold is known as the saturated water vapor pressure (SVP) level. When this level is exceeded, any excess water vapor condenses into rain. An increase in air temperature raises the SVP by 7 percent for every 1 °C rise. When there is insufficient moisture available from soil evaporation and plant transpiration to meet the saturation vapor pressure (SVP) level, the resulting difference is called a vapor pressure deficit (VPD).
The increase in SVP enhances the atmosphere’s drying strength during a VPD. This results in more extreme weather events, such as torrential rain that leads to flooding, as well as more frequent and prolonged droughts.
Bare ground heats up significantly more than ground covered with vegetation. The greater the vegetation cover, the more pronounced the shading and cooling effects. The image illustrates a 24°C (43.2°F) difference between the tall grass cover and the bare ground. A seven percent increase in drying for every degree Celsius rise corresponds to a 168% increase in drying.
Photosynthesis declines when atmospheric VPD increases because stomata close. Stomata are the breathing pores in leaves; they absorb air and, importantly, CO2 for photosynthesis. Plants shut their stomata when conditions become too dry to prevent water loss through transpiration. This action halts photosynthesis due to insufficient CO2 needed for glucose conversion.
Research indicates that VPD, instead of variations in rainfall, has a significant effect on vegetation growth. VPD strongly affects forest mortality, crop yields, and forest fires. Increases in VPD limit land evapotranspiration across various ecosystems because plants close their stomata to reduce water loss through transpiration.
Reversing Vapor Pressure Deficits
Contrary to the widespread belief that plants deplete soil moisture and should be removed to conserve it, the opposite is actually true. Plants condense atmospheric moisture at night by lowering their body temperature. This moisture forms droplets on the leaves, which then drip into the soil, enhancing its water content. It is the vapor pressure deficits (VPDs) that dry out the soil, not the plants.
Ground covers such as grasses and trees provide shade, cooling the soil and nearby areas. Planting shrubs, grasses, and trees helps to cool the climate by reducing VPDs.
The widespread regeneration of vegetation contributes to a cooler regional climate. As a result of regenerating forests, the eastern regions of the United States are now 1.5 °C (2.7°F) cooler than they were a century ago, while other areas have warmed by the same amount.
Adopting agroforestry systems will reduce VPD, cool the climate, increase soil moisture, and boost yields. These can be developed from row cropping, grazing, and horticulture practices such as orchards and vineyards.
Pasture Cropping
Similarly, pasture cropping is an innovative regenerative agriculture system where crops are strip-tilled into a perennial pasture instead of being cultivated on bare soil, which reduces VPD by maintaining a permanent ground cover. There’s no need to plow the pasture species or eliminate them with herbicides before planting the cash crop.
Colin Seis developed this in Australia. The principle is based on the ecological fact that annual plants thrive in perennial systems. The key is adapting this principle to the appropriate management systems for specific crops and climates. Pasture cropping can be used on permanent pastures and arable croplands.
Research conducted by Dr. Christine Jones indicates that this farming system significantly enhances soil fertility and increases the levels of soil organic matter (SOM).
Neils Olsen further innovated pasture cropping by developing equipment that integrates cultivation, mulching, aeration, and mixed species seeding into narrow tilled strips within the perennial pasture in a single pass. The field is grazed down or mulched before planting to reduce competition with the cash crop.
Pasture cropping is an effective method for increasing SOM. Olson was the first farmer to receive payment for sequestering soil carbon under the Australian government-regulated system. In 2019, he earned payment for sequestering 11 tons of CO2 equivalent per hectare per year under the Australian government’s Carbon Farming Scheme. He received payment for an additional 13 tons of CO2 equivalent per hectare in 2020. In 2024, he achieved 21 tons of CO2 equivalent per hectare (21,000 lbs per acre). (Neils Olson Pers. Com)
Greater Resilience in Adverse Conditions
Published studies indicate that regenerative and organic agriculture, utilizing the science of agroecology, is more resilient to anticipated weather extremes and can outperform conventional farming systems in yield under such conditions. For instance, the Wisconsin Integrated Cropping Systems Trials found that organic yields were higher during drought years and comparable to conventional yields in normal weather years.
Regenerative Organic Systems Increase Soil Organic Matter
This resilience is attributed to the increase in SOM. Research shows that regenerative organic systems are more effective at sequestering carbon-rich organic matter in the soil compared to conventional farming systems, offering multiple benefits listed below.
Improved Efficiency of Water Use
Research indicates that organic systems utilize water more efficiently due to improved soil structure and higher levels of humus and other organic matter compounds. Lotter and colleagues gathered data over a 10-year period during the Rodale Farm Systems Trial (FST). Their research revealed that the organic manure system and organic legume system (LEG) treatments enhance the soil’s water-holding capacity, infiltration rate, and water capture efficiency. The LEG maize soils exhibited an average of 13% higher water content than conventional system (CNV) soils at the same crop stage, and 7% higher than CNV soils in soybean plots (Lotter et al., 2003). The more porous structure of organically treated soil allows rainwater to quickly penetrate the ground, leading to reduced water loss from runoff and increased levels of water capture. This was particularly evident during two days of heavy rain from Hurricane Floyd in September 1999 when the organic systems captured nearly double the amount of water compared to the conventional systems.
Long-term scientific trials conducted by the Research Institute of Organic Agriculture (FiBL) in Switzerland compared organic, biodynamic, and conventional systems (DOK Trials) and revealed similar results, showing that organic systems were more resistant to erosion and more effective at capturing water.
The higher levels of organic matter allow the soil in the organic field to resist erosion in heavy rain events and capture more water. (Source: FiBL DOK Trials)
This aligns with numerous other comparative studies demonstrating that organic systems experience less soil loss due to superior soil structure and increased organic matter levels. Dr. Reganold conducted a long-term study and concluded: ‘We compare the long-term effects (since 1948) of organic and conventional farming on selected properties of the same soil. The organically-farmed soil had significantly higher organic matter content, thicker topsoil depth, higher polysaccharide content, lower modulus of rupture, and less soil erosion than the conventionally-farmed soil. This study indicates that, in the long term, the organic farming system was more effective than the conventional farming system in reducing soil erosion and, therefore, in maintaining soil productivity.’
Source: Rodale Institute
The same soil contains different levels of organic matter. The higher levels on the left make the soil more resistant to erosion and increase its water-holding capacity. In contrast, the soil on the right, with low levels of organic matter, is more prone to erosion, dispersion, and holds less water.
Humus, a key component of soil organic matter, is one of the main reasons organic soils are more stable and have a greater capacity to retain water. This is because it can hold up to 30 times its own weight in water, and as a ‘sticky’ polymer, it binds soil particles together, providing increased resistance to both water and wind erosion.
Humus can retain up to 30 times its own weight in water. It is a polymer that binds the soil together, providing stability and holding many of the nutrients that plants need to grow well.
The Importance of Organic Matter for Water Retention
There is a strong relationship between levels of soil organic matter and the amount of water that can be stored in a soil’s root zone. The table below should be viewed as a guideline rather than an exact set of measurements. Different soil types will retain varying volumes of water at the same organic matter levels due to factors such as pore spaces, specific soil density, and other variables. Generally, sandy soils retain less water than clay soils.
The table offers insights into the potential volume of rainwater that can be captured and stored in the root zone, in relation to the percentage of soil organic matter.
The same table in metric.
There is a significant difference in the amount of rainfall that can be captured and stored between the current soil organic matter (SOM) levels in most traditional farms in Asia and Africa and those in a well-managed organic farm with adequate SOM levels. This difference explains why organic farms perform better during periods of low rainfall and drought.
The 40-year Rodale Farming Systems Trial demonstrated that regenerative organic corn produced 31% more than industrial agriculture during droughts and had higher yields throughout the entire duration of the trial.
Avoiding bare ground by maximizing vegetation cover is crucial for reducing VPDs and increasing SOM. SOM enhances the soil’s ability to capture and retain rainfall, improve fertility, and prevent the erosion of fertile topsoil during heavy rain events. Adopting these regenerative organic practices is essential for reversing the trend of increasing adverse weather events and ensuring a productive future for our farming and ranching systems, as well as providing our civilization with healthy, nutritious, poison-free food. We can avoid repeating the past’s failures.
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