How plant species loss affects human health: A conversation with Cassandra Quave

Changing rainfall patterns, extreme weather events, ocean acidification: climate change is threatening species across the globe—many of which were already under pressure from other human activity. What will happen as plant species get displaced, become fewer, or disappear altogether? Could this have ramifications for human health?

This question led me to Dr. Cassandra Quave, an associate professor of dermatology and human health at Emory School of Medicine. Her research group documents the uses of botanical ingredients in traditional medicine in different sites across the globe and investigates the pharmacology of those medicines to understand what chemical constituents are responsible for their activities. Her team asks, “Is this particular herb safe? Is it effective for X, Y, or Z uses?” They then communicate their findings back to communities and use the findings as a starting point for new-drug development, primarily for infectious and inflammatory diseases. This work has taken her to the Amazon, the Balkans, the Mediterranean, and North Africa and has led to more than 130 scientific publications about the findings.

I sat down with Dr. Quave to discuss the important role medicinal plants play in protecting human health, including combating antibiotic resistance, and the threat climate change poses to these plants—and our future.

The following interview has been edited for length and clarity.

About Dr. Cassandra Quave

Dr. Cassandra Quave is an associate professor of dermatology and human health at Emory School of Medicine and Emory’s herbarium curator. She teaches courses on medicinal plants, microbiology, and pharmacology and leads natural-product drug discovery research. In her award-winning science memoir, The Plant Hunter, Dr. Quave tells the story of her personal medical journey and her quest to find new ways to fight illness and disease with plants. Dr. Quave’s research has been featured in many publications, including National Geographic Magazine, The New York Times, NPR, and PBS.

Annie Mullowney: Where did your passion for medicinal plants, food, and health come from?

Cassandra Quave: I was a pre-med student in college, very focused on trying to become an orthopedic surgeon. A lot of that was motivated by my personal experiences with surgeries throughout childhood to address my numerous congenital abnormalities in my skeletal system. I’ve had more than two dozen orthopedic surgeries in my lifetime to help correct my spine, hip, and leg.

But then I started to become more and more interested in the field of anthropology. I had an opportunity when I was finishing my junior year in college to work as a volunteer at a research camp in the Amazon on the Sucusari tributary off the Napo River. I worked with a local healer, Don Antonio, and had my eyes opened to the reality of medical care in developing countries and the heavy reliance on traditional medicines. I also saw that, in many ways, traditional medicines were being displaced by Western medicine, despite those Western medicines often being inadequate—in terms of both supply and local knowledge of how to access and use those medicines.

That experience got me really interested in—instead of being a physician and prescribing drugs—discovering new drugs. And better understanding the intersection between global health and future medical discoveries.

Annie Mullowney: Did you ever feel a push-pull between studying Western medicine and traditional medicines?

Cassandra Quave: I had a very classic focus on hard science and evidence-based medicine from a young age, both from my own experiences and through the many years I spent working in the emergency department in my hometown as a teen. So when I was doing that initial work in the Amazon, there were certainly things that I couldn’t quite understand or explain that in retrospect make a lot of sense.

For example, there was a tree called “sangre de drago” or the “dragon’s blood tree.” Don Antonio would use this tree for a number of different ailments or issues, and he kept emphasizing how it was a really powerful medicine. Years later, a formula of a mixture of compounds from that tree was the second FDA-approved botanical drug. When you put science behind it, oftentimes there are real, rational reasons why people continue to use these different medicines.

I think even a lot of physicians forget where many of our drugs come from. If you look, for example, at the World Health Organization’s list of essential medicines—medicines that are necessary to have in a primary care center—there’s a large list of molecules that were originally discovered in medicinal plants that have a history of use in traditional medicine. Digoxin, a heart drug, came from the foxglove—a use that goes back to William Withering in the 1700s. In the 1800s, morphine, which comes from the pod of the opium poppy, became one of the first drugs to have its chemical structure elucidated for pain. But it wasn’t until the 1960s that the National Cancer Institute started doing more searches for cancer medications from plants. And that helped to create more of the key drugs that are still used today, including paclitaxel, which you may know as Taxol, and camptothecin, which led to the development of topotecan.

I think about what I’m doing as bridging the gap between traditional medicine—where you may have spirituality, ritual, or other magical beliefs—and the chemistry that explains it.

“I think about what I’m doing as bridging the gap between traditional medicine—where you may have spirituality, ritual, or other magical beliefs—and the chemistry that explains it.”

Annie Mullowney: If you have a headache, are you reaching for an over-the-counter drug or something herbal?

Cassandra Quave: If it is a sinus headache, my go-to is Advil Cold & Sinus. This is ibuprofen plus pseudoephedrine, which is a molecule originally discovered in the ephedra plant. So I see it as a plant-based medicine. I also drink herbal tea. I drink mint tea for soothing a stomachache. I use all the things in my arsenal, and you’ll see the same in a lot of healers. There’s this idea that traditional medicine and modern medicine, which is built on the backbone of traditional medicine, have to be in opposition. I don’t see them as opposing at all. I see them as being a continuous line.

Annie Mullowney: Let’s talk about antibiotic resistance. What role do you see for nature in combating it?

Cassandra Quave: Antibiotic resistance is the major threat to medicine as we know it today. Without the ability to manage infections, our ability to provide care during childbirth, during cancer treatment, during even minor surgical procedures is going to be more limited. As of 2019, an estimated 700,000 people were dying annually due to untreatable infections. This is projected to reach 10 million a year by mid-century. It’s going to take a multitude of options to solve this problem.

Antibiotics are, in many cases, natural products. They were derived from microbes that were making these compounds to defend themselves or attack other organisms in their environment. What we’re trying to do is leverage our ability to read the language of nature and take the bits of that language that can offer humans the best defense against these microbial pathogens.

Classic antibiotics work by targeting the growth and survival of bacteria. The work that we’ve been doing has led to the discovery of molecules that don’t actually inhibit the growth or survival of the bacteria but instead act by limiting their ability to do harm. We think that this approach may be less likely to lead to antibiotic resistance because when you have a direct pressure on an organism, that organism will evolve, so you have progeny that’s resistant to that drug. We’re taking a side-door approach to diminish the ability of these microbes to cause harm.

And we’ve had a lot of success—for example, in our work on antibiotic-resistant Staphylococcus aureus or staph infections. You may also know of it as MRSA. These are drug-resistant staph, and we’ve been able to shut down their ability to communicate. Bacterial cells need to communicate with each other to coordinate their activities, so by shutting their communications down, we’ve also been able to stop their production of toxic molecules that destroy our tissues and lead to more severe infections.

So when I think about how plants might help us in the fight against antibiotic resistance, it might not be individual compounds from plants. Nature doesn’t always work through single molecules. It could be cocktails of compounds from plants or combinations of plant-derived compounds with other existing antibiotics to make the antibiotics that we have remaining work better.

Annie Mullowney: Could you talk more about the link between your work and climate change? Is it affecting our ability to create new drugs, fight antibiotic resistance, and generally to promote good health around the world?

Cassandra Quave: Climate change is putting a strain on plant populations across the globe. And as a result, the billions of people in economically developing countries that rely on medicinal plants as their only source of medicine are going to face greater and greater challenges in accessing medical care of their cultural traditions.

“The billions of people in economically developing countries that rely on medicinal plants as their only source of medicine are going to face greater and greater challenges in accessing medical care of their cultural traditions.”

I’ve seen this already—because of climate change but also just the expansion of human populations. The global population has surpassed eight billion people, meaning our footprint is expanding into more and more land areas. And more land is being used for agriculture—mainly soy and corn and palm oil products that are going into processed foods, into animal feed. So there are a lot of pressures faced in many different sectors that are putting more of these wild plants under threat.

Jan Salick, who has done amazing work in the Himalayas, has shown that a lot of plants are moving further and further up the mountains. After a while, you run out of mountain, and that’s a direct response to climate change.

Annie Mullowney: What do you wish the general public and businesses and policymakers understood about the links between health and nature? What actions should we be taking now for a healthier future?

Cassandra Quave: Health is complicated, and a lot of this is not in the control of our day-to-day choices. But I encourage people to get better connected to their own environment: maybe it’s as simple as learning the names of some of the trees in your neighborhood or doing some gardening. I feel very strongly that you are not going to advocate for nature if you have no relationship with the natural world.

We can also make choices with our spending, considering the damage certain products have on the world. I mentioned palm oil before. I’ve been to Sumatra. I’ve seen the territories where the forests have been ripped out and there’s hardly any habitat left. The local communities are losing the resources they need to survive and thrive in that forest.

About Into the Weeds

We at LEFF are, at heart, storytellers. We are dedicated to amplifying voices and causes from all over the world, regardless of gender orientation, race, or economic background. And the stories we tell as part of the Into the Weeds interview series are particularly important to us. We will be interviewing inspiring individuals whose work contributes to the achievement of the United Nation Sustainable Development Goals (SDGs) at every level; we’ll bring you insights from the leaders of global organizations, renowned experts and academics, and innovative local businesses.

Our goal for this series is the same one that underpins all of LEFF Sustainability Group’s client work: to use our storytelling skills to build awareness of the issues that threaten our planet and to draw attention to all the people, initiatives, and innovations that are fighting back.

But I think a lot of progress will have to come from government-initiated regulations and policies. For example, I would upend the entire Farm Bill. This is a post–World War II policy that emphasizes production of commodity crops by subsidizing corn, soy, and other crops. It’s the reason soda is cheaper than a health beverage or water. And it’s affecting our health. It’s also affecting our environment: the Amazon is being plowed down to plant more soy.

Another place to start would be to help restore what would be called “traditional knowledge” in another culture. Most people in the United States don’t know how to grow their own food. We should invest in educational programs to teach kids today not only how to better manage finances and make healthy food choices but also how to grow foods. This way people can supplement their diet with some fresh fruits and vegetables or, at a minimum, herbs.

If I could wave a magic wand, it would be to help people understand how our health as a species is tied to the health of our planet. We cannot have one without the other.

Behind the scenes

This interview is part of LEFF’s Into the Weeds interview series—a series that amplifies individuals whose work contributes to the achievement of the SDGs at every level. We’ll be bringing you insights from renowned experts and the leaders of global organizations and innovative local businesses. Annie Mullowney (she/her) is a senior editor for LEFF, and Clair Myatt (she/her) is the manager of LEFF’s Sustainability Group, for which Katie Parry (she/her) is the director.

Comments and opinions expressed by interviewees are their own and do not represent or reflect the opinions, policies, or positions of LEFF or have its endorsement.

Annie Mullowney

As a senior editor, Annie focuses primarily on developmental editing and drafting, helping clients sharpen their stories and tell them in a compelling way.