Modern, industrial agriculture produces large quantities of food at seemingly very low cost. High yields have been achieved all over the world through input-intensive monocultures and large feedlots, in a system which is predicated on uniformity. Farmers across the world are sold the same seed alongside a cocktail of synthetic fertilizers, pesticides and fungicides. They’re told that by following the formula they can achieve almost identical results in any soil, anywhere. After fifty years of this way of thinking we now have a world in which farming is responsible for extensive degradation of land and water, high greenhouse gas emissions, biodiversity loss, widespread malnutrition & obesity, and economic hardship for farmers. Our hyper-focus on producing cheap food has had devastating consequences and we need to radically reform our food system.

The statistics on just how uniform our food system has become are staggering. More than 6,000 plant species have been cultivated for food, but today just three crops – maize, rice and wheat – account for more than half the calories that we derive from plants. The FAO lists approximately 8,800 known livestock breeds, yet only 8 species provide 97% of global meat production. In this post I will argue that focussing on diversity is crucial to build a resilient agricultural system which regenerates the soil and halts, even reverses, biodiversity loss. 

Pests, diseases and weather

The majority of monocultures which dominate our landscape are made up of a single cultivar of the crop, in other words they are genetically identical. History shows us how dangerous this can be. The Irish Potato Famine in the 1840s led to the death of one million Irish citizens from starvation and another million refugees. The proximate cause of the famine was the fungal infestation Phytophtthor infestans, which reduced the majority of potatoes to slime. However, the lack of genetic diversity meant the famine was far more severe than it could have been. 

During the 1800s Ireland fed a rapidly growing population by vegetatively propagating the “lumper” variety of potato. This meant that all the clones were genetically identical and therefore equally susceptible to the fungal infection. Evolutionary theory suggests that a greater diversity would have meant that some potatoes would have contained the genes to resist infection, and more of those varieties could be planted in future years.  Later, scientists identified resistance genes in a potato from South America, where farmers have preserved the genetic variation of potatoes by growing many cultivated varieties alongside the potato’s wild cousins [source].

We have failed to learn from this tragic tale. Today just one variety of banana, the Cavendish, accounts for 47% of global production and virtually all of the bananas exported to the West. The Cavendish is currently being devastated by the spread of a strain of the Panama disease, known as TR4. Scientists are now rushing to create genetic changes to the variety which would make it immune to infection, but the system has put them on the back foot and threatened lives and livelihoods in the meantime. 

Building diversity into the system from the outset means it has much more in-built resilience: pests and diseases are far less likely to cause significant damage. Recent scientific studies show that a greater diversity of plants in a field gives insect pests a harder time as they have to keep adapting to new defences. Also the varying nutrient levels of plants in a polyculture (a field of multiple species) mean that pests are far less likely to flourish. Furthermore, predators benefit more than pests from increased diversity. Diverse plant communities, therefore, present the double problem for pests of less favourable conditions for them to thrive, and more predators.

The same trends are seen with fungal diseases. In one study disease-susceptible rice varieties, when planted in mixtures with resistant varieties over large tracts of land, had 89% greater yield and 94% reduced fungal blast occurrence than when planted in monoculture. Because of this experiment’s success, fungicidal sprays were no longer applied to these fields after the trial [source].

As discussed in a previous blog post, healthy soils have a huge variety of microorganisms which allows the soil to self-regulate and fight off threats (by, for example, crowding in such numbers around plants so as to not allow pathogens to take hold). A diversity of plants contributes to healthy soils by attracting a whole range of different microorganisms according to each plant’s specific needs. This creates a virtuous circle of healthier soils leading to less pest and disease outbreaks, which means less need for synthetic chemicals, which means healthier soils. It is in this way that merely increasing the number of species in a field can actively regenerate the ecosystem.

Diverse agricultural landscapes also provide more protection against climate shocks. A study of 181 communities of smallholders across Nicaragua after Hurricane Mitch found that farming plots cropped with simple agroecological methods, including green manure, crop rotation, legumes and trees, retained on average 40% more topsoil, higher field moisture, and suffered less erosion compared to conventional farms [source].

As our climate and weather patterns become more unstable, it is more important than ever that we build farms which can withstand such shocks. Moving away from monocultures and towards diverse, agroecological farming practices is an important part of this. 

Biodiversity 

Animal and plant species are declining at an alarming rate. Nearly 40% of the world’s plant species are at risk of extinction, insect and animal populations are estimated to have fallen by 59% and 60% respectively since 1970. Changing our damaging industrial monocropping practices to a diversity-focussed system has huge potential to change this. One recent study found that agroforestry systems (where strips of trees are planted in fields) had huge effects on wild pollinator numbers. Compared to monocultures, agroforestry fields had on average twice as many solitary bees and hoverflies, and in arable systems 2.4 times more bumblebees. Another research project discovered that diversified farms not only harboured more species of common birds than their monoculture counterparts but also provided shelter for some of the more threatened ones, hopefully allowing them to recover numbers. Birds are a good benchmark for the overall health of an ecosystem, as if each species doesn’t have the specific food and nesting sites it needs, it will disappear. A good number of birds present on a farm, therefore, implies a good range of both food and nesting sites, indicating healthy plant and animal biodiversity. 

But what about the yields?

Supporters of modern industrial agriculture claim that it is not possible to feed a growing global population without their high-input, high-yielding approach. Researchers have estimated that cereal yields per hectare more than doubled between 1961 and 2001 in East Asia and Pacific, South Asia, Latin America and the Caribbean due to high-yielding varieties. This did undoubtedly have a significant impact on economic prosperity and hunger levels in these areas, many of which have still-growing populations. So how can we hope to sustain or improve levels of nutrition across the world if we abandon these practices?

My response to this is twofold. Firstly, we already grow more than enough food to feed the world. Estimates indicate that we waste around one third of the food we produce at all levels of the supply chain from production, storage and processing through to consumer food waste. This issue has received widespread publicity in recent years and many initiatives are in place to tackle it. As long as it continues to receive the support and funding needed, we should be able to solve the problem of feeding a growing global population without even considering having to grow more food. 

Secondly, accurate yield measurements are complex and require much more nuance than simply looking at one field on one particularly high achieving year. Studies are starting to come out showing that initial high yields are now plateauing, or in some cases dropping off. A meta-analysis of yield developments around the world from 1961-2008 found that in 24-39% of areas growing maize, rice, wheat and soybean, yields either failed to improve, stagnated after initial gains, or collapsed. This is consistent with claims that industrial agriculture is causing widespread land degradation and is gradually eroding the land’s ability to provide a harvest for us at all. Moreover, nature is quickly adapting to our overuse of synthetic chemicals, which are no longer producing the results they once did: 266 species of herbicide resistant weeds have now been recorded globally, a number increasing significantly year on year. We need to change our approach and start working with nature, not against it. As discussed above, farming for diversity mimics natural systems and therefore provides a great deal of built-in resilience. It is this which will give us consistent yields in a climate-changed world. 

Change is coming

Fortunately, the modern industrial agricultural paradigm is being challenged from many angles, with multiple projects and initiatives designed to promote greater diversity on farms. The EU-funded project Diverfarming works directly with farmers to provide them with the data, tools and support they need to diversify their crops. The organisation Resilient Food Systems is working with farmers in Burundi to identify and characterize local crop varieties and breeds, and to identify ways to improve access, selection, and sharing of crop and animal genetic diversity at the community and national levels.

There are also organisations working with seeds to promote a greater diversity in fields, even when the whole field is planted with the same crop. The ‘YQ’ population wheat was developed by Martin Wolfe at Wakelyns and The Organic Research Centre (ORC) from 2001. The ‘YQ’ was bred by making 190 crosses among 20 different parent varieties and mixing all the resulting seeds. The outcome is a field of wheat with a huge amount of genetic variation. With this increased genetic diversity making more efficient use of soil nutrients and water, lowering plant disease and pest levels, the ORC found a huge improvement in yield stability. YQ wheat is now grown all across the country. The farmers are asked to save seed from each harvest, meaning that over time the population will adapt to the local ecosystem, creating even more resilience. This is how our ancestors used to farm, known as a landrace (a cultivated, genetically diverse variety of crop or animal which has evolved to suit the local conditions). Building on this success and creating populations of other crops is undoubtedly a crucially important part of the quest to build a food system fit for the future. 

It has become very popular in recent years to talk about diversity. Diversity in human groups and organisations can lead to new ways of thinking, enhanced empathy and less polarisation. A diversity of food in our diets leads to a healthy gut microbiome. Biodiversity is crucially important for a range of ecosystem services, as well as for the wellbeing of all the species we share this planet with. Now it’s time that the conversation around diversity is extended into agriculture, for it is only through redesigning our landscapes to include as many different edible and non-edible species as we possibly can that we will leave a thriving planet for our children and grandchildren to enjoy.