Left to its own defenses, a farm field growing a variety of plants will attract fewer insect pests than a field growing just one type of crop. This concept is not only ecologically logical; it is also proven, as researchers at UC Davis in their 2016 publication in Nature argue. While scientists and farmers have noted that difference for years, the reasons behind it have been poorly understood. The 2016 study explains that much of it may have to do with the nutritional needs of insects. They argue that returning plant diversity to farmland would be a key step toward sustainable pest control.

“Insects have a perfect nutrient level that they really like,” said lead author William Wetzel. “When it’s too high or too low, they do poorly.” The problem with monocultures, Wetzel said to Science Daily, is that if an insect likes the crop, that insect has a large food supply to draw from all in one place. Conversely, a field containing a variety of plants does not offer a large block of food for the insect, so it will not get the nutrients it needs to survive and thrive. “A monoculture is like a buffet for plant-eating insects where every dish is delicious,” Wetzel said. “A variable crop is like a buffet where every other dish is nasty.”

Simply put, monocultures promote pest infestation. Monocultures are also a ticking time bomb for devastating disease and other environmental stresses. Monocultures of an extractive agriculture model deplete the soils with each yield and in a particular way based on that particular crop. We all intuitively understand that a community that offers a varied toolkit will more successfully resist stresses imposed on it than an individual (a monoculture in this case). A monoculture only possesses one toolkit for change, making it less resilient to disease, fire, storms, and climate change. A biodiverse community, with only partial yield, provides its own nutrient replacement in a robust cycle of give and take.

So, why do big ag companies still use this overly simplified model for crop production?

Time and time again, we see continued use of this simplified model from traditional agricultural crops to tree plantations and ‘restorations’ in the ‘wild’.

Impact of Monoculture Use in Tree Plantations

In their 2019 study published in bioRxiv, Ekroth et al. concluded that genetically homogenous populations outside of agricultural systems are more prone to disease. The relationship between low genetic diversity and high disease incidence is referred to as the ‘monoculture effect.’ With human activities greatly reducing the genetic diversity of species worldwide, disease outbreaks will become more common.

Lodgepole pine has been introduced as a monocrop to several places outside its native habitat.

Lodgepole pine is coveted in Sweden as a crop tree given its ability to produce 36% greater total volume growth than the native Scots pine. But in New Zealand, introducing the lodgepole pine has threatened indigenous flora and fauna as well as visual and landscape values; it is now considered a weed species and seldom planted. Pests and pathogens associated with this pine may spread to native tree species. In British Columbia the Lodgepole Pine is also being planted as a monocrop outside its native range.

Monoculture tree planting has been common practice throughout interior British Columbia in Canada, but results in health problems as the species grows beyond the juvenile stage. In a 2015 issue of the scientific journal Forestry: An International Journal of Forest Research researchers W. Jean Roach, Suzanne W. Simard and Donald L. Sachs provide evidence why single-species planting after clear-cut or wildfire of lodgepole pine into an area outside its native range, just doesn’t make sense. The researchers examined damage and stocking in several fifteen to thirty-year-old lodgepole pine plantations previously declared ‘free growing’ in the highly productive cedar-hemlock forests of southeastern British Columbia. A free-growing stand of trees simply means that they are ecologically suited to the site and meet the government’s established criteria for height, density, spacing and overtopping vegetation.

Researchers found that close to half of the lodgepole pine trees showed unacceptable damage and were rejected as crop trees. The researchers recommended that single-species planting of lodgepole pine be curtailed in favour of using more diverse and locally adapted tree species. Monocultures are expected to be susceptible to catastrophic losses such as the mountain pine beetle epidemic in interior BC, and impacts posed by climate change. Given the already current stress of being planted outside its adapted native condition, monocrops of lodgepole pine are expected to not fair well. This is what is, in fact, happening.

Why The “Efficient” Approach of Monoculture Doesn’t Work

Ben Watts of Challenge Advisory shares a typical observation, “It’s common to picture a vast field containing wheat, barley, single species of fruit, or vegetable crops.” Watts explains the popularity of using monoculture in industrial agriculture: “Commercial modern agriculture has the primary aim of increasing yields and profits by cultivating one distinct crop. The principle belief which monoculture farmers have is that by providing the individual needs for just a single species of crop it will be more efficient and profitable. By cultivating a single crop only one method of harvesting needs to take place, hence boosting profitability for the farmer.”

But a simple crop—more convenient to grow and harvest—is also easier to wipe out by disease and pests.

Specialization only works in a ‘perfect world’ where variation and change is removed and controlled. And oddly enough, that ‘perfect world’ costs more—to humanity and to the rest of the planet’s environment. And it’s not even perfect. The hubris of a traditional engineering approach to life is the premise that we know how the natural world works. We don’t. So when we take something complex—like a natural ecosystem—and simplify it to make it ‘more efficient’ we often do the opposite; focusing on ‘function’ we actually create ‘disfunction.’

Because the engineering model behind monoculture farming does not account for environmental robustness, this model is doomed to fail. To prop up dysfunctional monocrops, the agricultural industry uses synthetic fertilizers, herbicides, insecticides, and bactericides. Soils become contaminated and natural communities that ensure overall health die. Crop yield also removes soil nutrients and generally degrades the soil to which the industry simply adds more chemicals in a vicious cycle of failure; this also ensures that crops will contain chemicals harmful to our health. 

Permaculture is a proven alternative method to monoculture. Based on the model of ecology, permaculture brings together key elements of a complete and functional ecosystem. Permaculture promotes biodiversity. Biodiversity ensures that the ecosystem remains intact and functional with different plants working together to keep the soil healthy and crops thriving. Permaculture fundamentally helps avoid having any component become too influential on the farm to the detriment of the remaining components (e.g., plants, bacteria, fungi, lichen, animals and insects.)

Challenge Advisory tell us that, “A variety of crops [and plants not functioning as crops] will allow crop failures without ruining the entire economy of a farm specializing in a monoculture such as coffee or tobacco.”

Successfully balancing efficiency with sustainability is a matter of scope. Fail to perceive wide enough and short-term efficiency will fail in the long-term. Sustainable productivity should be the long-game in agriculture. This relies on an ecological understanding of the role that biodiversity plays in a sustaining agriculture. We need to embrace nature’s chaos and rely on nature’s complexity to succeed.

How do we do that?

We use the principles of ecology, not engineering.   

The Need to Move from Engineering Crops to Ecologizing Crops

For close to half a century, agriculture has been viewed as an industry of components toward high and efficient yield of ‘product.’ This has translated into ‘engineering crops’: the use of synthetic chemical-assisted monoculture. Engineering crops considers these plants as non-living without relationship in a community. A crop’s living relationship with its environment—from soil to other plants, insects, fungi, and animals—is ignored and not addressed. An otherwise complex natural ecosystem is over-simplified to a few biological and chemical aspects to grow and harvest.

Engineering crops to increase efficiency and productivity has at its root a single-minded mindset based on component-thinking: grow a single crop to streamline harvesting methods and boost profit (not considering the role of diverse community in individual plant health and resilience) and make selling more convenient (not considering the role of climate and environmental changes in markets). When component-thinking is used without considering how these components work in relationship, efficiency is eventually compromised and fails.

Creating efficiency of components without considering relationship is a cheat.

Ecologizing crops considers relationship of components, how things work together within a functional ecosystem. Ecologizing crops considers them as alive and in relationship in a robust interactive community. This model (used in permaculture farming and forest gardens) acknowledges the role of biodiversity in achieving a functional ecosystem—and usable crops. Using ecology as a model instead of engineering as a model, agriculturists rely on Nature’s ancient knowledge in resilience and productivity. By bringing in complexity, the ecosystem’s functionality takes care of itself and its components—including the target crops. As the researchers at UC Davis pointed out, pests are controlled through a diverse buffet. There is no need for synthetic chemicals to assist; crops remain resilient to damage and to stresses such as disease for much longer.

Short-term yield may be smaller in a complex-ecosystem permaculture than in a simple-ecosystem monocrop, but long-term yield (and profit) will be higher and will sustain far longer.    

References:

Ekroth, Alice K.E., Charlotte Rafaluk-Mohr, and Kayla C. King. “Diversity and disease: evidence for the monoculture effect beyond agricultural systems.” bioRxiv June 12, 2019.

Roach, W. Jean, Suzanne W. Simard, Donald L. Sachs. “Evidence against planting lodgepole pine monocultures in the cedar-hemlock forests of southeastern British Columbia.” Forestry 88(3): 345-358.

Wetzel, William. C., Heather M. Kharouba, Moria Robinson, Marcel Holyoak, Richard Karban. 2016. “Variability in plant nutrients reduces insect herbivore performance.” Nature, DOI: 10.1038/nature20140