man letting sandy soil through his fingers

You really need to know this

Sometimes it is necessary to take stock, to sit under a shady tree and contemplate what brought you to this tree. Then imagine what happens next, given the journey taken and the opportunity to ponder.

Smell the roses, hear the birds singing, and breathe.

So urge the authors who gave us shelves full of self-help books that contain page after page taunting us toward awareness aided and abetted by a Tic Toc army of gurus, all filming advice for our benefit. 

I jest. 

Awareness is not just good; it is great. Knowing yourself has always been the key to a healthy, fulfilled existence. There is nothing wrong with sitting under a shady tree, nothing at all.

Indeed, awareness of self might be the essential step to understanding everything else. Because there is everything else. We all live in and of this world, and the world has changed. 

Contemplation time should include musing on the consequences of what humanity has done and will do in the coming decades.

Here are a few sobering facts drawn from a review by researchers at the University of East Anglia in the UK, my alma mater, that are not in the self-help books and don’t feature in the social media algorithms but are essential to know. 

In the spirit of self-help, sustainably FED brings you these gems and adds some thoughts on how to contemplate these confronting facts about, you guessed it,

… soil.

In the last 150 years, more than half of all soils have been damaged 

WWF. 2018 Soil erosion and degradation

Half is significant. Measured as area, it amounts to 50 million km2 which is half the habitable area of the earth; only the habitable area includes 39 million km2 of forests that are, presumably, not damaged that much. So the 50% is really due to the impacts on soil from agricultural practices, especially on the 11 million km2 of arable land.

Damage is just the word a green NGO would use to describe human actions. It sits nicely alongside the impacts and threats that the WWF website offers up. 

How do you damage soil? 

Well, agriculture uses soil to grow plants that otherwise would not be growing in that soil. And when anything is used, it wears and tears, often imperceptibly at first, but over time there is less organic carbon, less structure, reduced biological activity, poorer water balance, and overall a reduced ability to support plant growth. Farmers know this and add fertiliser, water and pesticides to keep their crops growing. Damage is not the correct word, but when humans use soil for agriculture, we change the capability and condition of the soil.

When contemplating one half, there is always the half not damaged. There are soils in the world that are still in their natural state, and we can learn from how they function and how not to damage them.

Then comes the critical fact of 150 years. 

A century and a half is a blink in evolutionary time and not very long in ecological time, usually measured in 100s of years. Most of what WWF calls damage came about since the advent of internal combustion engine tractors, roughly the 1920s. It is a force trauma, a near immediate impact but with lasting consequences.

Half is a lot, and it happened in an instant.

Ponder these two facts for a few breaths, and the magnitude of the challenge of human survival and the cause become much clearer.

Degradation of soil has been accompanied by the attrition of greater than 50% of the soil organic carbon (SOC) stock in some cultivated soils, with over 2 billion ha affected globally  

Lal R. 2004 Soil carbon sequestration impacts on global climate change and food security. Science 304, 1623–1627

A typically nerdy way to say that agriculture mines soil carbon. 

Half the soil carbon content across 20 million km2 of land is no longer in the soil. This happens because when native vegetation is cleared for crops or grazing, the carbon cycle established over millennia from the interplay between the soil, climate and vegetation is disrupted. Soil is exposed to the sun and the wind, soil structure is impacted as the trees are ripped up and the ploughs level the land, water balance changes with all sorts of consequences for the biology and chemistry of the soil… I could go on, but for contemplation purposes, here is the crux.

Loss of soil carbon changes soil condition and reduces soil capability compared to its potential.

Soil becomes less good at being soil. 

Soils subjected to degradation become a significant emission source of CO2 to the atmosphere. Soil degradation has liberated an estimated 176 Gt of soil carbon globally; a significant quotient when contextualised against the 800 Gt C held in the atmosphere. 

Janzen H. 2004 Carbon cycling in earth systems—a soil science perspective. Agric. Ecosyst. Environ. 104, 399–417. 

If you were wondering where the soil carbon went, well, it went up into the sky. Yep, most of that carbon hitched itself to oxygen and became CO2, carbon dioxide, a gas that makes up about 0.04% of the atmosphere. It might be a trace gas but, as just about everyone now knows, it absorbs infrared radiation and acts like a blanket to warm the earth, a greenhouse gas. It is also the gas, given the nominal global warming potential of 1, and provides a common scale for measuring the climate effects of different gases.

Soil degradation from human land use has released roughly 22%, nearly a quarter, of the CO2 in the atmosphere, almost all of it in the last 100 years since the advent of modern agriculture.

A quarter is significant too.

Averaged over the last 150 years, the soil carbon loss rate equates to 1.6 ± 0.8 Gt C yr−1. In context, anthropogenic global carbon emissions in 2000 were estimated to be 7.5 Gt C yr−1 (i.e. the rate of annual SOC loss is approx. 20% of this value). 

Van Vuuren DP et al. 2011 The representative concentration pathways: an overview. Clim. Change 109, 5.

Contemplate the 176 Gt C released into the atmosphere as CO2 from soils over 100 years. And then realise that CO2 concentration in the atmosphere is double what is was prior to the industrial revolution.

So when the media tells you climate change is a fossil fuel problem they are correct—the latest global CO2 emissions for 2020 from energy (roughly 70% of all emissions) were 8.6 Gt C.

But then, here is the thing… 

Agriculture, forestry and land use change is reported to be directly responsible for approximately 18–24% of total anthropogenic GHG emission each year. 

Friedlingstein P et al. 2019 Global carbon budget 2019. Earth Syst. Sci. Data 11, 1783–1838. 

We have not stopped using land and we can’t.

Agriculture has to produce 22 trillion calories a day just to keep people alive. Fail to meet this ongoing demand and people will starve, children die or live with debilitating malnutrition.

So climate change is an agriculture and soils thing too. 

It is not politically correct to point out the emission profile of agriculture except for those who want us to give up meat, but it exists. Land clearing and intensive crop production are just as significant as cows belching methane.

Contemplation can be painful.

This conversion of natural ecosystems to managed systems is reported to deplete SOC stocks by an average of 60% in temperate regions, and up to 75% in the worst affected regions of the tropics, accounting for losses of up to 80 t C ha−1.

Lal R. 2004 Soil carbon sequestration impacts on global climate change and food security. Science 304, 1623–1627. 

All the contemplating completed up to this point is exhausting, you probably need a latte from the coffe cart that just pulled up into the car park behind the tree. The barista is proudly spruiking a Tanzania Peaberry Coffee that just won an award and, sure enough, the Arabica bean delivers medium body and delightful fruit-toned acidity. 

Coffee is Tanzania’s largest export crop at around 40,000 metric tons annually. The Tanzania Coffee Board had a plan to double production in the country from 2011 to 2021 but  missed its 2017 target by 41% due to decreasing yields. In most regions of Tanzania a coffee tree becomes economically unprofitable after 20-25 years and most of the 240 million coffee trees around the country have exceeded this age but intercropping with banana and other crops has caused soil depletion.

This coffee anecdote brings inequity into the contemplation.

Where the people are poorest and the need greatest, so the soils are generally poorer and more prone to carbon loss. This is more than a coincidence. The rich, fertile soils of Europe, North America and parts of China contributed to productive agriculture in these regions and then to their ongoing economic success. Equally, poor soils are a big part of why famine and food insecurity are real in Africa.

This is the rabbit hole of contemplation. Once it becomes about people it is deep and frequently dark.


What sustainably FED suggests

It is crucial to appreciate that soil resources, although abundant and long lasting, are non-renewable on an anthropogenic timescale. 

Where rates of soil loss/degradation outpace rates of biogenic and geological soil replacement/recovery, the sustainability balance is tipped. Globally, poor soil management and loss of SOC have exacerbated topsoil losses to a point where they are 10–40 times greater than natural replacement rates. In the USA, topsoil loss rates are roughly ten times that of replacement; while in India and China, loss rates exceed 30–40 times natural replacement.

Failures in soil management decrease crop yield and impair society’s ability to grow sufficient crops. Crop productivity loss of 0.3% per year are reported from degraded SOC stocks; a decrease that could aggregate to an average of 10% reduction in yields by 2050 (with the worst affected regions experiencing up to 50% yield reductions). Across the European Union, 45% of agricultural soils are considered impaired or very impaired in SOM content.

And so it goes.

As you sit under the tree contemplating these scary facts that make the consequences of climate change seem balmy…

Breathe.

Humanity is so vast and voracious that any sane person is overwhelmed by our impact… 

Breathe again.

Now imagine what could be done to slow everything down and make repairs.


Science Source

Keenor, S. G., Rodrigues, A. F., Mao, L., Latawiec, A. E., Harwood, A. R., & Reid, B. J. (2021). Capturing a soil carbon economy. Royal Society open science, 8(4), 202305.


Hero image from photo by FORREST CAVALE on Unsplash

Mark

Mark is an ecology nerd who was cursed with an entrepreneurial gene and a big picture view making him a rare beast, uncomfortable in the ivory towers and the disconnected silos of the public service. Despite this he has made it through a 40+ year career as a scientist and for some unknown reason still likes to read scientific papers.

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