Nature's Medicine Cabinet: The Nexus of Climate Change, Public Health, and Secondary Plant Metabolites
By Charlie Dubbe, Head of Regenerative Partnerships, Agrology
A Call for Resilient Agriculture
As we face the challenges of climate change and environmental degradation, the adoption of regenerative agricultural practices to revitalize our soil health, our community health, our farms’ financial health, and our wider ecosystem health becomes absolutely imperative. As I heard Dr.Jonathan Lundgren, director of Ecdysis Foundation say last week at a regenerative field day:
“You don't have to change. No one will make you adopt these regenerative practices. But if you don’t, you’ll lose the farm... It's that simple folks.”
I was struck by the bluntness of this statement, and yet I could feel the truth in it. If we don’t course correct now, we will lose the farm. And on the largest collective level, that means losing a habitable planet that can self regulate and heal, restoring balance and harmony to ecosystems that we have thrown so far out of balance.
As we confront the realities of climate change, the role of secondary plant metabolites (PSMs) in imparting resilience to crops becomes increasingly important. Climate change is expected to intensify both biotic and abiotic stressors on crops, leading to reduced yields and compromised crop quality. Secondary metabolites offer a buffer, enhancing a plant's innate ability to withstand these stressors. For example, certain metabolites can help plants tolerate drought conditions or resist temperature fluctuations, thereby securing agricultural productivity in an increasingly unpredictable climate.
The Vital Role of Secondary Metabolites in Climate Resilient Agriculture
In the evolving world of regenerative agriculture, establishing and understanding the links between life in the soil and rhizosphere and primary/secondary metabolite production in plants will unlock incredible value for farmers, and create more medicinal food for all of us. While primary metabolites like sugars and amino acids are essential for basic plant survival, growth and reproduction, secondary metabolites play a critical and nuanced role in plant defense and quality. These organic compounds, though not directly involved in growth, are vital for a plant's resilience against a myriad of stressors. Beyond enhancing plants' resilience and immunity to pests and diseases, these compounds are linked to medicinal effects of high-quality food and herbal remedies.
When Hippocrates said, “Let food be thy medicine, and let medicine be thy food,” he was unknowingly referring to these compounds. We know that antioxidant-rich foods such as dark chocolate, blueberries, and pecans are good for us because they eliminate free-radicals in our cells that can lead to cancer, but we rarely consider why plants create these antioxidants in their own bodies, or how these compounds are manufactured via a biochemical exchange between plants and the life in soil.
Secondary Metabolites: Nature's Medicine Cabinet
Secondary metabolites are a plant's natural defense mechanism. They are nature’s medicine cabinet, with a diverse set of biochemical cures for every known ill. As Stephen Harrod Buhner points out in his fantastic book on the topic The Lost Language of Plants - “as plants grow, they produce a complex assortment of compounds to maintain and restore health. These include: tannins, antibiotic, antimicrobial and antifungal compounds: mucilages, gums and resins; anti-inflammatory compounds; analgesics and so on.”
Buhner describes how the secondary compounds in plants “vary by species, season, time of day, individual plant, and environmental stressors. Plants continually receive and process information from their environment and they use it in determining the amounts and types of secondary compounds they need to produce and in what combination.” (Buhner, p. 159). This is where the magic of soil life enters the stage. As many of you probably know, mycelial fungi are just one of many soil microbes that feed plants information via biochemical pathways. There is constant communication via the original “world wide web” of mycelial fungi that spread throughout healthy soils, sharing information between plants, between life in the soil and plant roots, and even from plants back to the soil.
A classic example of a highly medicinal PSM is salicylic acid, a self-produced and administered medicine in plants that also serves as powerful medicine for humans and animals. Like most of these PSMs, salicylic acid has a variety of uses and expressions within plants depending on the dosage, environmental conditions, and chemical combinations released within. It can stimulate plant growth and root development in lower doses, but in higher doses actually inhibits plant growth. It also has powerful anti-inflammatory effects and can be rapidly translocated to wherever it is needed. Amazingly enough, you can probably find this powerful plant medicine in your own cupboards, as it is the precursor to aspirin, one of the most widely used anti-inflammatory medicines in the world (Buhner, p.156).
Some other noteworthy secondary plant metabolites are phenolic compounds, flavonoids, terpenoids, alkaloids, saponins, tannins, polyphenols, and cyanogenic glycosides. The quantity and diversity of these biochemicals are breathtaking. According to Yeshi, et al. “More than 8000 phenolic compounds are reported from plants, of which half of them are flavonoids (approximately 4000–4500 compounds).” As revealed by the name flavonoids, these compounds give flavor and color to foliage, fruits and veggies, but in addition “phenolics and flavonoids are well-known for their antioxidative and anti-inflammatory properties” (Yeshi, et al. 2002).
According to this study on plants’ secondary metabolites by Yeshi, et al. Plant secondary metabolites “are vital for human health and form many pharmaceutical drugs’ backbone. Indeed, more than 25% of the existing drugs belong to PSMs.”
The Biochemical Library of PSMs
Other well known compounds that are part of the amazing library of secondary plant metabolites are nicotine in tobacco, caffeine in the coffee plant, cocaine and other stimulating alkaloids in coca, terpenes and cannabinoids in cannabis and hemp, and morphine in poppies. And the diversity of different PSMs is quite literally beyond measure. Just within the realms of terpenes alone there are “more than 35,000 different terpenes having been characterized to date,” with a huge range of function, chemical structure, and potency (Twaij, et al.).
All of these compounds play a vital role in maintaining and restoring health in the plants that produce them. Plants produce and use them in response to a constant information flow they are receiving from their environment, mostly through soil communication pathways, but also via aromatics. This information often comes from other plants: when certain plants are attacked by a pest, they will give their surrounding ecosystems a warning via volatile aromatics or terpenes, or via biochemical communication pathways through the fungal mycelia that connect their roots.
One amazing example of this comes from the douglas fir trees, which create a sophisticated chemical response to infestations of spruce budworm. When they sense that they are being attacked by the spruce budworm, they begin releasing a complex mixture of volatile oils, or terpenes from their needles, such as a-pinene, camphene, b-pinene, myrcene, limonene, and many others. Some of these, such as boryl acetate, are strongly toxic to budworms, and other terpenes “affect the ability of the budworm to find trees, to feed and reproduce.” These terpenes and aromatics also give surrounding trees the heads up to shore up their defenses, because an attacker is present in the ecosystem. What is even more surprising about this process of biochemical defense, the trees keep the budworming guessing by varying “the composition and production of terpenes each year [to decrease] the ability of the budworm to develop widespread immunity to specific compounds.” (Buner, p. 160). This is akin to the antibiotics that humans use continually evolving and changing in their chemical composition and dosage to keep these bacteria guessing, and unable to develop antibiotic resistance.
Figure 1:
The three main types of Secondary Metabolites. Source: Zhao, Yiu, et al. 2023
Impact on Quality and Characteristics
Secondary metabolites also significantly impact the quality characteristics of agricultural produce, wines, coffee, chocolate, plant medicines, etc. Taking wine grapes as an example, the polyphenols and tannins, which are secondary metabolites, not only contribute to the vines’ resilience against fungal infections but also profoundly influence the color, taste, and texture of the wine. These compounds are some of the most important compounds that winemakers look for in high-quality grapes and wines, and are part of wines’ unique expression of terroir and vintage.
How do PSMs reflect the vintage? The process looks something like this: the particular characteristics of that season create biotic and abiotic stressors on the vines, which modulate how and when the vines produce secondary plant metabolites such as tannins, polyphenols, and other flavonoids. These compounds are the literal expression of the unique context of that vintage and the terroir, which is “understood to be the result of soil type, climate, landscape, topography, biotic interactions and agricultural practice.” (Johnston-Monje, et al. 2023).
In cannabis and hemp, terpenes like myrcene and limonene, beyond imparting distinct aromas, have been found to play a role in plant resistance to thermal stress. It is important to appreciate that these compounds are key contributors to the therapeutic qualities of these plants, reducing anxiety and stress in human beings. In both of these examples, we see how the PSMs that help plants resist stress through modulating immune responses have similar effects in human bodies, as well as huge impacts on quality, aroma, and medicinal characteristics.
Microbial Activity: The Engine Driving Secondary Metabolite Production
The enhancement of secondary metabolite production in plants is intricately linked to the microbial activity in the soil. A healthy, diverse soil microbiome, a defining result of regenerative agricultural practices, facilitates a symbiotic relationship between plant roots and the soil food web. The biochemical feedback involved in this dialogue between living soil and living roots has been shown to stimulate plants to produce a wider array of secondary metabolites.
As Jontston-Monje et al. describe in their 2023 study titled Plant microbiomes as contributors to agricultural terroir, “biogeographical variation of soil microbiomes” is an important factor that modulate the “medicinal… and saponin content of Panax notoginseng growing in different parts of China (Wei et al., 2020), concentrations of the “impact aroma” molecule rotundone in Shiraz grapes (Gupta et al., 2019), and the metabolome of Australian Pinot Noir wine” (Liu et al., 2020).
The soil microbes act as catalysts, enhancing nutrient absorption and signaling mechanisms in plants, which in turn ramp up the production of these vital compounds. Secondary metabolites are created within the plant in response to the conditions that surround it, and a key way that plants receive information about their surroundings is from the biochemical pathways that occur in the rhizosphere. These signals from certain soil microbes “are able to alter plant chemistry by changing the way a plant grows and metabolizes. Root growth can be dramatically enhanced by underground bacterial signals which alter plant phytohormone production and gene expression…” (Johnston-Monje, et al. 2023).
John Kempf, founder of AEA, has provided a big inspiration for this article through his teachings and podcast. He describes how when plants are grown in soil that is full of life, with high levels of biological nutrient cycling and nutrient availability, the microbial community provides these plants with their complete macro and micro nutrient needs at every stage of their phenological development. This complete nutritional support allows plants to move to higher levels on the “plant health pyramid.” It is only at the highest level of the pyramid, when plants have optimal nutrition provided a biologically active and diverse soil food web that senses the plants nutritional needs and provides for them at all times, that these plants have increased secondary metabolite production. Kempf makes the bold claim that plants that are this healthy “can become completely resistant to diseases and insects.”
Figure 2: The Plant Health Pyramid. Source: John Kempf and Advancing Eco Agriculture
The Feedback Loop Between Soil and Plants:
As described above, the biochemicals created by soil microbial life can alter plants’ chemistries, hormone levels, phenological expressions, growth patterns, and more. The life below the surface of the soil is a key shaper of the characteristics of plant life above the surface. But this dialogue is not just one way, it's a two way street of bio-chemical communication and feedback loops. Buhner describes how “plants are all chemists” in his spellbinding book The Lost Language of Plants. In this book, he describes how plant chemistries are incorporated into and change the characteristics and functioning of the soil in numerous ways. One of the principal ways that plant chemistries find their way into the soil is through plant litter, which carry plant chemistries down into the soil as they are broken down by insects, microbes, fungi, and bacteria. He describes how “the rates at which the chemistries in litter…move back into the ecosystem vary depending on the ecosystem involved, from weeks to centuries. During that entire time they modify soil chemistry and soil community composition. Anything that changes the surface plants’ chemistries changes the composition of the underlying soil, humic acid, soil community, and local streams” (p. 166). He also describes how soil actually acts as a storage unit, or battery, for complex plant chemistries and compounds. Humic acid “uncouples many plant compounds, separating them into their constituent chemistries, detoxifying them, and keeping soil fertile…It stores the separated chemistries within itself as stable complexes where it can, when inputs from the ecosystem indicate the necessity, recombine them into needed compounds and re-release them into the ecosystem.”
The most amazing part is this: all of these chemistries revolve within a web of life, maintaining the balance and health of an ecosystem through extremely complex and poorly understood feedback loops. Buhner describes how “through tightly coupled feedback processes information on the chemistry reserves stored in humic acid feeds back into the aboveground plant communities, indicating what plants should grow in what combination” ie: succession planning. In addition to this, biochemical feedback is given to plants on “what kinds of chemistries they should produce to keep the soil healthy. This is why it is not possible to increase soil fertility through human action. Unless interfered with, the soil in natural ecosystems is always at maximum fertility” (p. 165).
Soil Health: The Cornerstone of Regenerative Agriculture
The practices of regenerative agriculture – such as cover cropping, reduced tillage, diverse crop rotations, and integration of livestock into production systems – foster a rich soil food web, brimming with life and activity. This vibrant soil life and diversity of microbial communities, in turn, supports and enhances the production of secondary metabolites in plants. By focusing on soil health, regenerative agriculture not only sustains and improves crop yields while simultaneously reducing the needs for inputs such as fertilizers, pesticides and fungicides, but also elevates the intrinsic value of the crops through enhanced quality. Plants with higher secondary metabolite production are more nutritious, more flavorful, and have more medicinal compounds such as antioxidants, flavonoids, anti-carcinogens, and anti-inflammatory compounds. Who wouldn’t want a higher quality crop, with more nutritional and medicinal density, that requires less outside inputs, and also has an improved ecological footprint?
Measuring Outcomes in Regenerative Agriculture
In regenerative agriculture, we focus on outcomes, not just practices. The context of each farm is so individual that what works well on one field may have a completely different outcome on another. I go into more depth on this topic in my first article on Linkedin, entitled “Regenerative Ag: A big tent.” This is why we measure impact, using techniques such as consistent soil samples that measure labile and permanent carbon stocks, water infiltration rates, bulk density, microbial biomass, etc. Another powerful approach to real-time, continuous soil health monitoring is Agrology’s Arbiter system. It is the only commercial system that continuously measures soil health via soil respiration. This can allow growers to see the impact of their inputs and practice changes on soil carbon dynamics, and respiration gives a clear indication of the levels of soil life. To see what this data looks like in a side-by-side regenerative vs. conventional trial on a commercial farm (ie: the real world, not a laboratory), see this case study we created with O’Neill Vintners and Distillers.
A Sustainable Future: Reducing Dependency on External Inputs
One of the most significant benefits of increased secondary metabolite production is the reduced reliance on external inputs like fungicides and pesticides. These chemicals, while effective in the short term, need to be used in higher and higher dosages as pests and diseases develop resistance. We have seen this most clearly with glyphosate, the active ingredient in Roundup. Because of its extensive overuse, this chemistry has now lost almost all of its efficacy, and now needs to be used with a variety of other chemistries, increasing the cost to the farmer as well as the environmental impact.
The use of pesticides, fungicides, and insecticides also has long-term ecological and public health repercussions, including the devastation of soil life, long lasting water pollution, and the degradation of human gut biomes. It’s been very inspiring to see our friends and collaborators at Napa Green implement a plan to phase out the use of glyphosate across all of their accredited vineyards, and this seems to be the beginning of a larger tide change in agriculture.
By harnessing the natural defense mechanisms of plants through enhanced secondary metabolite production, regenerative agriculture offers a sustainable and ecologically responsible alternative. We can rely on the natural biochemical defenses that plants have developed over hundreds of thousands of years, solutions that don't endanger ecological or human health, and don't cost farmers a thing.
Secondary Plant Metabolites: A Biological Buffer to Climate Change
By developing practices, principles, and measurement tools to enhance soil health we can also boost secondary metabolite production in plants, which creates the elasticity and resilience we will need from our crops in this age of climate change.
This is the best way we can shore up our agricultural system against the coming onslaught of challenges and stresses that will be (and already are) headed our way in a more volatile climate. As climate change continues to intensify, we will see increases in abiotic stressors such as drought, high salinity, unseasonal frost, extreme heat waves, out of balance soil pHs, flooding, etc. Already, it is estimated that “more than 50% of crop production losses are due to abiotic stresses” according to Andaman Ag. The best way to boost our crops, and ultimately our food systems’ ability to weather these challenges is by increasing the life in our soil.
And increasing plants' natural resilience to extreme weather isn't the only way that healthy soils help our agricultural system weather the storm of climate change. Healthy soils also reduce flooding with higher water infiltration rates, and retain that water for longer in what we call the “soil carbon sponge.” This means we lose less water (and topsoil) during heavy winter storms, and we can make it through the long hot summers with plenty of moisture for crops to grow.
We can do this through regenerative agriculture, and we must. It doesn’t hurt that along the way we’ll likely make our food healthier, tastier, and hopefully be able to pay growers a premium for those improvements.
By recentering the life in our soils as a KPI of what a successful farm looks like, we can build a more resilient, nutritious, and sustainable agricultural system. This approach not only benefits the environment but also supports the health and well-being of future generations directly. As we have seen in the sections above, the compounds that plants produce as medicines for themselves also serve as medicines for human beings.
A Call to Action
In conclusion, the role of secondary metabolites in enhancing plant resilience and quality is integral to the promise and success of regenerative agriculture. As we navigate the challenges of our time, focusing on the principles and practices that enhance soil health and thereby increase secondary metabolite production in plants is crucial, but so is measuring these impacts with ground-truth data.
I invite you to join us at Agrology in embracing regenerative agriculture. Together, we can transition to practices that enhance soil health and measure the impact of this shift on crucial parameters like soil carbon stocks, soil respiration, and microbial activity. Let's work together to build a resilient, nutritious, and sustainable agricultural system for our planet.
References:
A note on references. I did my best to cite all information included in this article, but things inevitably fall through the cracks. I am standing on the shoulders of giants, and much of the information and arguments included in this article are based on my synthesis and analysis of thousands of articles and podcasts, way too many to reference here. A special thanks and bow of appreciation to John Kempf and Stephen Harrod Buhner for their teachings on this subject. If I missed anything, if you want to learn more about this information, or the sources of my data, please reach out to me at Charlie@agrology.ag.
Andaman Ag. Primary and Secondary Metabolites, Climate Change, and Yields.
David Johnston-Monje, Laura Isabella Vergara, Jessica Lopez-Mejia, James Francis White. Plant microbiomes as contributors to agricultural terroir. Frontiers in Agronomy, 19 October 2023.
John Kempf. Plant Health Pyramid. Advancing Eco Agriculture’s youtube channel.
Menaka Thakur, Sujata Bhattacharya, Prem Kumar Khosla, Sunil Puri. Improving production of plant secondary metabolites through biotic and abiotic elicitation. Journal of Applied Research on Medicinal and Aromatic Plants, Volume 12, 2019.
Yan Zhao, Guanze Liu, Feng Yang, et al. Multilayered regulation of secondary metabolism in medicinal plants. Mol Horticulture 3, 11 (2023). https://doi.org/10.1186/s43897-023-00059-y
Stephen Harrod Buhner (2002). The Secret Language of Plants: The Ecological Importance of Plant Medicines to Life on Earth. Chelsea Green Publishing.
Twaij BM, Hasan MN. Bioactive Secondary Metabolites from Plant Sources: Types, Synthesis, and Their Therapeutic Uses. International Journal of Plant Biology. 2022; 13(1):4-14. https://doi.org/10.3390/ijpb13010003