Figure 1: A farm during the Dust Bowl in the 1930s, Texas. Due to intensive plowing and drought, 3.5 million Americans had to migrate away from this hellish and barren landscape / Dorothea Lange/Farm Security Administration via Library of Congress
The main reason you are here, reading this article while sipping a cup of coffee, instead of working 12 hours a day in a rice/wheat field is because modern farming produces enough food for our growing world population while needing a fraction of the workforce it did 100 years ago. And for that, you can thank the Green Revolution. This series of events that would revolutionize farming started in Mexico in the 1950s and by the end of the 1960s had spread through the rest of the world. It consisted of developing chemical fertilizers and pesticides, increasing irrigation practices, and implementing high-yield crop varieties able to make the most of these innovations.
There is no denying this revolution saved billions of lives by avoiding world hunger, increasing food production greatly, and supporting population growth. This takes us back to you, dear reader, one of the 7 billion people this revolution brought along. And unfortunately, you may be of the last generation to reap the benefits of this green time-ticking bomb.
Strong medicine and strong side-effects
To simplify, we can compare the Green Revolution to an antibiotic aiming to eradicate agricultural pests - insects and illnesses, low soil fertility, ancient crop varieties, etc. By using this superweapon, agriculture productivity peaked. However, just like a strong antibiotic, the revolution did not only eliminate the “bad” part of nature - it also weakened our ecosystems as a whole, even the “good” part. Agrochemicals and pesticide overuse led to increased risks of runoff in groundwater, river, and local ecosystems. In some cases, these products may also severely affect farmer communities due to the toxicity of products used, such as chlordecone or DDT (franceinfo and IARC, web).
Insect and arthropods’ biodiversity has been plummeting. A study published in Nature recently showed that insect numbers were cut by half in intensive farming areas impacted by climate change. Their diversity was also cut by a third (Outhwaite et al., 2022). Yet, these beetles, crickets, and bees are vital for pollination and natural pest management. Without them, most fruits and vegetables would simply not grow. Worldwide, 40% of all insects species are threatened, and the main reason is agrochemicals used by agriculture - alongside climate change and invasive species.
Then, just like with antibiotic overuse, the nasty bacteria started to become resistant - and when the pests fight back, our food security is on the line. Weeds resisting common products such as glyphosate are a growing problem for farmers (no pun intended). Mismanagement of fertilization due to a lack of fertilization guidelines is also widespread and leads to low nutrient-use efficiency and loss of nitrogen through leaching or volatilization, affecting respectively water cycle and climate change, as NOx is a potent greenhouse gas. It is responsible for 18% of agriculture-related GHG emissions, which account for 23% of global GHG emissions (IPCC, 2020) themselves. Talking about climate change, the IPCC warned in their AR6 report about rising average temperatures and altered rainfall patterns, raising the risks of agricultural drought.
All these issues, combined with socio-economic challenges that local communities face because of a globalized economy and unstable prices, call for a rethinking of what agriculture should be. We should seek a new treatment for the ills our miracle pill has brought. To preserve our food security and fight against climate change and biodiversity loss, we need new practices to adapt to an ever-changing world. Else, our grandchildren will face devastating consequences for today’s agricultural practices.
Figure 2: The "Windshield phenomenon" is an observation made by automobilists since the 2000s that very few insect now crash on windshields compared to 50 years ago. Since 2017, multiple studies have documented arthropods' decline.
The soil is the base: how conservation agriculture builds resilience
To fix our food systems, we need holistic approaches. Instead of seeing a farm as a linear supply chain: the soil - the fertilizer - the crop - the machine - the harvest, we need to think of it as a web of interconnected actors: soil, flora, fauna, humans, and the environment. This way of thinking applies to many approaches, broadly called “regenerative agriculture” (Schreefel et al., 2020), but today we will focus on conservation agriculture (CA).
This approach is a solid candidate for fighting against climate change in agriculture and recreating healthy ecosystems ready to support efficient and clean farming. Why is it called conservation agriculture, you ask? Because it preserves the soil. And you should never forget: the soil is the base. And I will explain this with the 3 principles of conservation agriculture (CA) in order of ease of implementation.
Species diversification
First and foremost, a healthy soil is one where diverse species can thrive. It can be accomplished by crop sequencing and combining different crops in the same field. No one said it was easy, though. It requires careful planning and observation since the optimal crop rotation depends on crops, climate, and soil type. In fine, it promotes microbial and faunal diversity in the soil, enhances soil structure, and helps to complete nutrient cycles. Don’t forget, the soil is the base!
Permanent soil cover
Usually, the field is left barren and empty between two harvests of wheat or rice. Any heavy rain erodes this clean slate and washes away all its precious nutrients and organic matter down the drain. Under conventional agriculture, soils erode 10 to 100 times faster than they form. Once the soil is gone, it is effectively gone forever at our timescale, and agriculture is doomed to fail on this land.
This is why keeping a protective layer of vegetation on the soil surface at all times is the second principle. It can be a cover crop or mulch. It helps to suppress unwanted weeds and protects from said erosion.
Reduced tillage or no-till
Now, for the famous part: if you have ever heard of conservation agriculture, it’s likely you have also heard “no-till”. This is exactly what it sounds like: farmers try to reduce soil disturbances to a minimum, thanks to direct sowing and fertilizer application. This allows for reduced machinery use, thus reducing the GHG emissions from farming (West and Marland, 2002). But it also allows for better carbon sequestration in the long run (La Scala et al., 2006).
Figure 3: Number of publications including “conservation agriculture” in the title published on the Web of Science during the past 11 years. Source: FAA with WoS data
Why is conservation agriculture crucial to feed our grandchildren?
Now, hear me out. Conservation agriculture is not our only tool to build tomorrow’s food systems, but it should be our foundation. Because it’s a stable base to further build on. Because it safeguards our food systems against climate change and soil erosion. Still not convinced?
Here are 4 facts to change your mind.
Biological pacemaker
I told you at the beginning how conventional farming harmed biodiversity. Despite this harm, ecosystems can prove to be surprisingly quick to bounce back when given the chance. In CA, reduced tillage and residue retention increase topsoil organic matter. In other words, more food and shelter for microbial communities. As a result, microbial diversity and biomass increase. Symbiotic fungi are suspected to make the most out of this shift, and they can help plants to gather nutrients and water more efficiently during droughts (N. Verhulst, 2010).
Earthworms also thrive thanks to reduced disturbance and increased organic matter to chew on. They are more diverse and active in fields under CA (Palm et al., 2014). This takes us to advantage number two.
Agricultural drought is not as problematic as it should be
A very funny thing to do when reading scientific papers is finding when the researcher got caught off-guard by their own results. Concerning the resilience of CA to drought, increased density of soil and reduced overall porosity should make this system less efficient at stocking water.
“These changes would be expected to lower water infiltration rates in NT (no-till) compared to CT (conventional tillage); this however has not been shown”
(Palm et al., 2014)
Spotted!
This is explained by better soil stability and interconnection of pores thanks to earthworms. In practice, fields cultivated with CA absorb rainwater better and have higher soil moisture. A meta-analysis found yields on average 7.3% higher than conventional agriculture during droughts (Pittelkow and Al, 2014).
Figure 4: Even heat-tolerant species like sunflower can be impacted in case of extreme drought. Here, in a conventional field.
Your descendants will be able to farm this land too
Every year, 43 billion tons of land are eroded worldwide. A study published by Borrelli and al. in 2020 showed how IPCC climate change scenarii would influence this figure depending on land-use change and agricultural practices. The regions most affected by erosion would be tropical regions, eastern North America and Subsaharan Africa. Erosion caused by water will increase between 30 and 66% in the next 50 years.
This same report recommends that “ the crops under CA would need to increase globally to 60%” to reduce erosion as best as possible. Why is this practice so effective to reduce erosion?
Permanent soil cover plays an important role in protecting the soil against erosion. It essentially acts as a buffer to avoid crusting after heavy rains. The active fungi and bacteria produce organic “glues”, giving the soil a cohesive and stable structure able to withstand rainfall and floods. Finally, the incorporation of organic matter regenerates soil similar to what happens in a natural forest.
At civilization timescales, conservation agriculture “produces erosion rates much closer to soil production rates and therefore could provide a foundation for sustainable agriculture” compared to plow-based agriculture
(Montgomery, 2007)
Figure 5: In the AR6 report, the IPCC showcased how soil erosion would evolve depending on different global warming scenarii. RCP 2.6 is the optimistic scenario, whereas RCP 8.5 is a worst-case scenario
More money in your pockets
If you are still not convinced, the magic word should achieve to convince you of the system’s viability. CA farms are often more profitable than conventional ones.
How is this even possible? The first component of this success is consistent yield. A meta-analysis considered 193 studies and found that both absolute and relative yield stability were equal between conventional and no-till agriculture (Knapp and van der Heijden, 2018). The only situation where no-till is not recommended is cold humid climates, where it underperforms compared to conventional agriculture.
If yields are pretty much the same, why is CA more competitive? The main cause is a reduction in production costs. If you are a farmer and you don’t need to till, you pay less fuel, you reduce labor costs and you also save money on maintenance. Judice and al. found a $16.28.ha-1 reduction in costs per tillage avoided, in sugarcane systems in the USA. Economic details and cost savings vary depending on the commodity and pedoclimatic conditions, but generally speaking, CA is more competitive than conventional agriculture when it comes to farmer income, even across widely different socioeconomic situations (Tambo and Mockshell, 2018) (Erenstein et al., 2012).
But why doesn’t everybody do it?
With these many advantages, you might scratch your head and wonder why it is not popular. Today, CA systems make up 9% of arable land worldwide and are predominantly used in South and North America (Table 1).
Table 1: Global area distribution of CA by continent; Source : (Kassam and al, 2014)
CA is a relatively recent innovation, and its spread outside of America is a slow process, although research has picked up the pace in the past 15 years. It often takes a few years to acquire the technical knowledge to run smoothly a CA farm as this is very site-specific, and high investments in machinery for direct seeding and mulching may discourage transitions. For smallholders, animal-drawn and hand tools are developed and spread from South America, as cheaper alternatives to machinery (Erenstein et al., 2012) The lack of public policy and recognition in Europe and developing countries is also a threat to implementation.
At last, in traditional smallholder subtropical farming systems, other activities may compete with mulching, such as fodder, fuel, or construction material.
Despite all of this, CA is today more and more recognized as productive, economically viable, and ecologically sustainable. Its use has only been increasing since the 90s and it still grows to this day. With better policies and pressure from climate change and the issues brought by conventional agriculture, conservation agriculture may be the backbone of our future food systems.
Sources
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