The Water Cycle and Global Cooling
Much like with the carbon cycle the water cycle had been entirely disrupted by destructive farming practices. This is not surprising as the two cycles are interlinked. The upside of this is that the same regenerative actions that are used to fix the carbon cycle, and get carbon back in the soil, fix the water cycle by reinstating the soil carbon sponge. With carbon and water back in the soil photosynthesis will be optimised which in turn will start to cool the earth.
There are actually two water cycles the large and the small. The small cycle takes place on land and deals with transpiration from plants and the rain that this ultimately causes. The large water cycle is the cycling of water between land and sea. Both of these cycles have been disrupted by the ravages of degenerative agriculture and both are desperately in need of healing.
Image: courtesy NOAA National Weather Service
The small water cycle is driven by transpiration so in order for it to function the ground needs to be covered in growing plants which release water vapour as they photosynthesise. Bare ground heats up the environment in two ways, by heating up directly from the sun's radiation and by the lack of plants transpiring to cool the local environment down. This results in a breakdown in the small water cycle. People believe that bare soil is caused by a lack of rain, but bare soil actually causes a lack of rain by breaking the small water cycle. Bare soil is generally caused by poor management. If you look at the South African and Australian wheat regions for most of the year bare soil is exposed to the sun and the wind.
Like with the carbon cycle, where the carbon is in the wrong place, the water in the small water cycle is also in the wrong place. It is also in the atmosphere rather than in the soil.
Water vapour forms around a nuclei and one such nuclei is a special bacteria that becomes airborne through transpiration. It is this bacteria based water vapour that seeds the clouds of the small water cycle leading to rain. When photosynthesis is not optimal transpiration decreases and rainfall decreases. There is another type of nuclei that water vapour forms about and that is minute airborne particles of dust. As we plough, leave fields bare and overgraze the desertification results in more and more dust but it also results in less and less rain. This dust based water vapour does not seed clouds in the same way as the bacterial nuclei do. The vapour does not coalesce as easily to form rain drops and the end result is this water vapour remains in the atmosphere as a haze, a haze of greenhouse gas.
Along with getting carbon back in the soil we need to reduce this dust and get the water it holds out of the atmosphere and back into the soil. When that water is back in the soil it has multiple positive effects. It is no longer a greenhouse gas, it grows plants, cools the planet and revitalises the small water cycle, stabilising rainfall so that it is no longer a case of famine or feast. Another win, win, win.
Soil Carbon Sponge, Walter Jehne
Secondly due to the excessive runoff from degraded soils and man made infrastructure like roads and buildings there is too much water in the oceans . Water that should seep into soils and be held there runs off and is flushed out into rivers and ultimately into the sea, leaving the soil short of moisture when the sun comes back out. All of which means less photosynthesis, less transpiration and less rain. By fixing our carbon cycles this water will infiltrate the soil better and the increased soil carbon will hold it there. Walter Jehne refers to this as the "soil carbon sponge".
"Collectively, the trees of the Amazon rainforest create a "vertical river" even greater than the Amazon river itself" - Antonio Donato Nobre
"on a sunny day a good-sized tree may transpire more than 100 litres of water - a process that represents three times the cooling power of an air conditioning system in a five-star hotel room" - Judith Schwartz
Infiltration and holding capacity
Once you have transpiration and rain you need to make that rain effective by capturing it in the soil so that it can be available for plants long after it has stopped raining. Water infiltration rates are crucial and in order to achieve this you need healthy, well aggregated soils with large pores. Your soils should be able to absorb all the water from a more than average rainfall, it shouldn't pool on the surface and it shouldn't run off. Soils that can absorb water can also hold it and the capacity to do both of these comes down to carbon.
By increasing his soil organic matter (SOM) Gabe Brown has been able to increase his water infiltration by a factor of 16. When he started regenerative farming his SOM was 2% and his infiltration rate was 12mm per hour, anything greater than that was lost due to runoff or evaporation, but a few years later with his SOM at 6% that rate had increased to more than 200mm per hour!
A 1% increase in soil carbon increases the capacity of that soil to hold water by 170 000 litres per hectare (a standard domestic swimming pool holds about 30 000 litres of water so that's nearly 6 pools!). What this translates into is an additional 17mm of rain that can be held in the soil with 1% increase in soil carbon. Water infiltration and storage are becoming more and more crucial as temperatures rise and soils dry out. With its increased SOM Gabe Brown's soil can hold an additional 68mm of rainfall.
As climate change is making our rainfall more erratic, often with fewer more extreme rain events, this capture and storage of water is becoming more and more crucial.
"Give me Iowa and I'll change the Weather" - Ridge Shinn, grass-fed rancher
Video: Plants cool the world
Podcast: Walter Jehne discusses the Soil Carbon Sponge and Cooling the Climate