Agriculture is an industry that is facing multiple crises converging upon it at once. A serious drive to increase its sustainability and efficiency is underway, and it involves re-examining every resource and method used today. The ongoing population explosion has resulted in the agriculture industry attempting to ramp up production. The widely used traditional farming methods have exposed weaknesses in the industry’s ability to produce food while protecting the environment on which it depends. The soil that farmers rely on has been one of their worst hit resources, and the mindset of the industry must change to preserve soil health and consider how soil health is connected to major sustainability issues, as highlighted by McBratney’s work on soil security (Figure 1). Topsoil – the uppermost layer of soil on which agriculture is based – is not often considered to be a non-renewable resource, which has led to a short-term mindset that is in dire need of change. A study by  Montgomery has found that agricultural lands are suffering from the erosion of free soil particles at a  rate 10-100 times faster than the process which creates soil, which truly highlights why this must now be thought of in a non-renewable context. Soil scientists are emphasizing the degradation caused by traditional farming techniques, and studies such as those by Borrelli et al. show us how urgently agriculture around the globe must adapt to protect the health of our soils.

Borrelli and his team performed an extensive study that showed how the increased need for agriculture is influencing soil erosion. Between the years 2001 and 2012, the study found that the changes of other types of land use to cropland have accounted for 80% of the increase in global average area-specific soil erosion. This results from cropland having the highest average soil erosion rate of any type of land studied (see Figure 2 below). Thus the ever-expanding need for food production will fuel the amplification of soil erosion and its consequences. These increases found by  Borrelli were computed using the farming methods most frequently used around the world today. To fully understand how these common methods are driving the rise in global erosion rates, we should examine each one’s relationship to the soil. 

The first farming method that first comes to mind when someone is thinking of unsustainable practices is usually that of pesticide use. We have all read the stories about the overuse of chemicals polluting water or harming local environments. Some application methods are so reckless and excessive that they have led to the poisoning of the pollinators that farmers and ecosystems rely on.  This pollution is often not limited to the environment of the croplands and can impact the ecosystems surrounding them. Their effects pose a serious threat to the physical and chemical health of soils. A  recent study by Tang et al. found that the overuse of pesticides has put a lot of soils on agricultural lands at risk of biodiversity loss and environmental instability. The results showed that a startling 64%  of global agricultural lands had pesticide residues above the no-effect level of more than one active ingredient. Several high-biodiversity areas and water-scarce areas showed residue concentrations 1000  times that of no-effect level, which places these soils at extremely high risk of pesticide-related degradation. If agriculture continues failing to properly plan the usage of these chemicals, there is a  risk of losing soil before it even physically erodes. These polluted soils would be unsuitable for producing food or sustaining an ecosystem that could benefit the industry. A lack of biodiversity within the soil will increase the rate at which it physically degrades as it fails to properly support the plants that would have grown in it. 

Pesticides are not the only way by which farming can cause chemical damage to the soil. When you think of a patch of non-cropland, such as a forest, you don’t picture the entire plot as being only one species of plant. Even wild grasslands are not entirely uniform. But when you think of the typical farmer’s field, it is generally rows and rows of the same crop. When farmers plant the same crop on the same field for harvest after harvest these fields are called monocultures. A study by  Mendes-Olivera et al. found how the lack of diversity resulting from monoculture decreases overall soil health. Single-species croplands have a small range of root sizes and are unable to develop a complex and healthy physical structure. Plants of the same species require the same minerals and compounds to grow, so their continued presence will rapidly deplete the soil of these minerals. This gradual deterioration makes the soil less productive for that crop and any others which rely on any of those minerals. Monoculture’s advantages of being easy to plant do not fully make up for these serious flaws in considering their impacts on soil health. Therefore, we must seriously reconsider when monocultures are appropriate. 

Picture a plot of farmland again, but this time one which is being prepared for planting; you will probably picture a farmer breaking the earth with their plow. You may even romantically or nostalgically see it being pulled by an ox or donkey out in a lonesome, bare field. But when it comes to the physical erosion of soil, the practice of tilling is no friend to a soil’s health. By plowing, the farmer breaks down the healthy structure the soil had developed through the present root systems and interconnection of inorganic and organic particles. Without the natural structure of the soil holding it together, wind and water can more easily carry loose soil away. We can see this and the negative impacts of the aforementioned loss of particles reflected in the study done by Montgomery, which has alarming implications for how long these soils will last. Richie’s study on global soil longevity found that under the current conventional methods, 16% of soils had a lifespan of under 100 years. This alone should raise an alarm in your head, but Ritchie also found that bare soils, which are often how farmers leave their fields between seasons or when they are no longer productive, have an estimated  34% with lifespans under 100 years. It is clearly evident that soil needs to be talked about in a much more urgent manner in light of this work. 

You might now be thinking about how these methods directly impact farmland use around the world. As soil condition deteriorates and erosion increases, the amount and quality of food we are able to produce will decrease. We need to protect all of our resources to fight malnutrition and poverty while promoting sustainability. Continuing these practices is removing the source of food and income for societies around the world, which is a massive dereliction of duty. The short-term mindset of too many people in the industry today and the prevalence of large agrochemical companies mean that many farmers just turn to fertilizers and pesticides to offset the short-term losses. Now that we are familiar with the negative impacts chemicals have on soil health, we know this will only further accelerate long-term degradation. We can clearly see that a change in mindset towards the long-term is needed to protect current and future food supplies and farms. 

Looking back at Figure 1, you can clearly see that soil health is very interconnected with other aspects of the environment. From this, you know that the impacts of the previous paragraph are only some of the consequences, and this subset occurs entirely at the farm site. The connections between soil and the environment result in this degradation negatively affecting the nearby environments. All of the erosion described in Borrelli’s work produces a large number of loose soil particles on the move,  and they all have to go somewhere. As water takes this loose dirt to a nearby waterway, its arrival seriously clouds it in a process known as siltation. This water is now much dirtier, which means its quality for drinking and swimming is significantly worse. Humans will have to clean it at a great cost (if they can afford it). Some animals will simply get sick and be forced to look elsewhere for drinking water, especially if this erosion brings chemicals with it. The ecosystem of these waterways will also be negatively impacted, as sight-reliant creatures will lose the ability to navigate or find food. As these particles settle to the waterbed in a process called sedimentation, waterways can change course as a  result, leading to flooding that can displace societies and ecosystems. While these chemical and physical effects are quite harmful to ecosystems, soil health also is connected to the omnipresent threat of climate change, as it can act as a carbon sink when in good health. Thus, protecting soils should form an integral part of all our climate and sustainability goals. 

These burdens are not equally shared across all of the countries in the world. The previously mentioned fertilizers and pesticides help farmers continue to work in the short term only when they can afford them.  Farmers who cannot pay to supplement their field’s waning nutrients must either change the way they manage their fields or watch as harvests simply do not produce what they used to. Farmers in poorer countries then fall further behind since they cannot afford to protect their yields or soil health using conventional methods. They sometimes resort to cheaper and more harmful chemicals to do so, as they do not have access to the knowledge or resources for improving soil health. Figure 3 shows some negative trend in a nation’s (logged)  GDP and their average soil erosion rate on cropland. It also shows how countries further from the equator (larger latitudes) also have lower erosion rates. Thus, we can see the poorer, hotter countries in sub-Saharan Africa will suffer from the worst erosion rates on their soil,  and this is one of the specific findings in Borrelli’s report. Support from scientists from around the world needs to be directed to these higher-risk areas. 

We can now see the extensive challenges facing a farmer’s relationship with soil today and how this varies around the world. The physical erosion and chemical deterioration as a result of common agricultural practices have been slowly creating and expanding issues that have not been immediately identified as being a consequence of soil health. Now that we are aware of these causes and symptoms, we can diagnose the issues our soils have and begin to prescribe and apply treatments appropriate to each issue. In this article, we focused on what is going wrong in the bulk of the agricultural industry. Scientists and farmers have been coming up with unique solutions to tackle each of these problems. Coming up soon will be a short-form series on the methods that are already in use on some farms that are contributing to noticeably healthier soils and ecosystems.

Bibliography  

Borrelli, P., Robinson, D. A., Fleischer, L. R., Lugato, E., Ballabio, C., Alewell, C.,  Meusburger, K., Modugno, S., Schütt, B., Ferro, V., Bagarello, V., Van Oost, K.,  Montanarella, L., & Panagos, P. (2017). An assessment of the global impact of 21st century  land use change on soil erosion. Nature Communications, 8(2013), 1-13.  https://doi.org/10.1038/s41467-017-02142-7 

Lugato, E., Leip, A., & Jones, A. (2018, 2 26). Mitigation potential of soil carbon  management overestimated by neglecting N2O emissions. Nature Climate Change, 8, 219– 223. https://www.nature.com/articles/s41558-018-0087-z 

McBratney, A. (2014, January). The dimensions of soil security. Geoderma, 213, 203-213.  https://doi.org/10.1016/j.geoderma.2013.08.013 

Mendes-Oliveira, A. C., Peres, C. A., de A. Maués, P. C. R., Oliveira, G. L., Mineiro, I.  G.B., de Maria, S. L. S., & Lima, R. C. S. (2017, November 8). Oil palm monoculture  induces drastic erosion of an Amazonian forest mammal fauna. PLoS ONE, 12(11), 1-19.  https://doi.org/ 10.1371/journal.pone.0187650 

Montgomery, D. R. (2007, July 11). Soil erosion and agricultural sustainability (P. A. Matson,  Ed.). Proceedings of the National Academy of Sciences of the United States of America,  104(33), 13268-13272. https://doi.org/10.1073/pnas.0611508104 

Ritchie, H. (2021, January 14). Do we only have 60 harvests left? Our World In Data.  https://ourworldindata.org/soil-lifespans 

Tang, F. H.M., Lenzen, M., McBratney, A., & Maggi, F. (2021, March 29). Risk of pesticide  pollution at the global scale. Nature Geoscience, 14, 206-210. https://doi.org/10.1038/s41561- 021-00712-5