5.3 Psychological Benefits of Plants
5.4 Physiological Benefits of Plants
5.5 Medicinal Benefits of Plants
5_The-Role-of-Plants-in-Human-Well-Being
Hall & Knuth: A Review of the Emotional and Mental Health Benefits of Plants
Hall & Knuth: Available Resources and Usage of Plant Benefits Information
Hall & Knuth: Physiological Health Benefits
Hall & Knuth: Social Benefits
International Center of Ethnobiology
TeachEthnobotany
The Role of Plants in Human Well-Being
Overview
Title image: "Appalachian Trail, Smoky Mountain National Park, TN" by Abhishek Chinchalkar is marked with CC BY-NC-ND 2.0.
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Introduction
Lesson Objectives
Describe the various ways plants impact human well-being.
Distinguish between the terms psychological and physiological.
List research-based psychological and physiological benefits of plants.
Key Terms
medicinal - substances and other treatments that are used to cure illnesses
physical - relates to the body
physiological - the way that living bodies function
psychological - relates to the mind and feelings
restorative - refers to the ability to restore consciousness, vigor, or health
Introduction
For most of human history, our health, wellbeing, and success have been intertwined with our ability to interpret the environmental cues around us, which are often provided by plants. People who were better able to interpret these signals from plants had an easier time finding food, water, shelter, and refuge from predators. There is a growing body of research that demonstrates the physiological, physical, medicinal, and psychological benefits of green nature to humans. Several such studies are referenced in this lesson.
Some studies explore benefits from active gardening activities, such as tending a vegetable or flower garden or taking a nature hike; while others attempt to quantify benefits from passive experiences, including viewing nature from a window or the presence of a houseplant in a room. The amount of plant life varies between areas, and many of these studies use the term “green space” rather than “plants” or “gardens.” What is “green space”? In their comprehensive series of literature reviews on the benefits of plants and horticulture, Dr. Charles Hall and Dr. Melinda Knuth write, “The term ‘green spaces’ has been used extensively to refer to areas of urban vegetation including public and private parks and gardens, residential landscapes, and urban forests and other municipal landscapes.”
Readers should keep in mind that many of the findings referenced in the first three sections of this lesson are from correlational studies rather than true experiments, and correlation does not necessarily mean causation. Correlational studies are an important first step researchers take to determine whether future controlled studies are worthwhile.
Prominent Theories
When researchers explore the relationship between plants and nature on human health, they develop a theory to explain their findings. Three prominent theories in the fields of environmental psychology, environmental sociology, and socio-horticulture include Dr. Stephen and Dr. Rachel Kaplan’s Attention Restoration Theory, Dr. Roger Ulrich’s Stress Recovery Theory (a Psycho-Evolutionary Theory), and Dr. Edward O. Wilson’s Biophilia Hypothesis. While some people may have learned to love plants, gardening, and nature through taught experiences, each of these three theories proposes that unlearned, evolutionary factors are also important considerations when describing our positive response to nature.
Stress Recovery Theory (Psycho-Evolutionary Theory)
The framework for Stress Recovery Theory was proposed by Dr. Roger Ulrich (formerly of Texas A&M University, currently with the Chalmers University of Technology in Sweden); this framework can be found in his landmark work “Aesthetic and affective response to natural environments” (1983).
Ulrich and co-author Russ Parsons later described the theory in “Influences of passive experiences with plants on well-being and health” (1992):
The long evolutionary development of humankind in natural environments has left its mark on our species in the form of unlearned predispositions to pay attention and respond positively to certain contents (e.g., vegetation, water) and configurations that comprise those environments. People respond especially positively to combinations of contents and forms characteristic of natural settings that were most readily exploited by premodern humans, or were most favorable to ongoing well-being or survival… Ulrich postulates that quick-onset affective or emotional reactions – not cognitive responses – constitute the first level of response to nature, and are central to subsequent thoughts, memory, meaning, and behavior with respect to environment.
Dr. Ulrich has measured physiological and psychophysiological responses to stress, including heart rate, blood pressure, muscle tension and brain waves, after exposure to different stimuli. He and other proponents of Stress Recovery Theory have found that exposure to natural environments—even just a view from a window or a poster of a natural scene—can reduce tension and enhance recovery from stress (Ulrich, 1984; Ulrich et al., 1991).
Attention Restoration Theory
Dr. Stephen Kaplan and Dr. Rachel Kaplan of the University of Michigan proposed Attention Restoration Theory in their book The Experience of Nature: A Psychological Perspective as an explanation for why natural environments seem to have a restorative effect on attention.
Any discussion of this theory should include a description of “mental fatigue.” Mental fatigue is caused by spending time in a state of directed attention where focus must be maintained by suppressing distracting stimuli. This is especially common in modern environments where cell phone notifications and advertisements are constantly vying for attention. School environments also require a great deal of directed attention to successfully complete assignments and learn new information. The ability to maintain directed attention decreases over time. The result of prolonged directed attention is mental fatigue (Parsons, 1991). Symptoms of mental fatigue include irritability, increased incidence of mistakes (Kaplan, 2001), stress (Han, 2009), aggression and decreased impulse control (Kuo & Sullivan, 2001). As a person becomes more mentally fatigued, they become less able to evaluate a situation rationally and more likely to have an unnecessary outburst (Kuo & Sullivan, 2001).
Natural environments that are rich in “fascinating” stimuli that intrigue the senses can be suitable treatment for mental fatigue. According Attention Restoration Theory, natural environments that spark human fascination provide an opportunity for the mind to recover from mental fatigue (Parsons, 1991). Other treatments for mental fatigue include taking a vacation and, to some extent, sleep (Kaplan, 1993). Attention restoration is facilitated by a landscape that meets certain criteria (Kaplan, 1984). An example of a restorative landscape would be a “mysterious” environment, where participants in the environment feel drawn in to explore around a bend of a curving path or over a hill just out of view.
Since the type of environment is of primary importance in attention restoration theory, much of the research supporting the theory typically involves some type analysis of the qualities of the landscape (like mystery). However, Rachel Kaplan (1984) once asked, “Is presence in the setting sufficient to reap the benefits? Or is some involvement or commitment [activity in the environment] on the part of the individual essential?” Kaplan went on to note three types of involvement in the landscape that could also contribute to Attention Restoration Theory. The first type of involvement is active involvement in the natural environment, which could include gardening or a walk through the neighborhood. The second type of involvement is observing (passive involvement), such as a looking out on a natural scene from a window or watching plants grow and develop. The third level of involvement is on a conceptual nature. Conceptual involvement has to do with knowledge and imagining one’s participation in a natural environment through an activity like planning a garden or reflecting on a prior outdoor experience.
The Biophilia Hypothesis
Dr. Edward O. Wilson (1929 – 2021) studied at the University of Alabama and Harvard University, where he went on to hold a faculty position from 1956 until 1996. He began his career as a biologist focused on the study of ants. In fact, he discovered the first colony of fire ants in the U.S. near the port of Mobile in Alabama.
Wilson’s work as a biologist led him to study social behavior of insects, animals, and humans. He became one of the foremost naturalists of the 20th century, writing several books on science and conservation. In 1984, Wilson wrote Biophilia, in which he proposed that humans have an innate tendency to seek connections with nature and other forms of life. Wilsons’ Biophilia Hypothesis attempts to explain why humans have a preference for the natural world and makes a strong argument in favor of conservation.
The Biophilia Hypothesis has led to an increase in biophilic design. Biophilic designs incorporate biophilia into the built environment and are becoming more common in architecture, interior design, and other related fields as a complement to green design. While green design strives to decrease the environmental impact of the built environment, biophilic design includes natural elements and features as a way to facilitate human connection with nature.
Psychological Benefits of Plants
Research in environmental psychology, socio-horticulture, and related fields have shown that even in our modern society, humans still experience psychological benefits from spending time with plants. Several studies have shown that access to green nature, a view of green space from a window, the presence of living houseplants, and even images of nature have positive psychological benefits. Humans in modern societies spend most of their time indoors (US Dept. of Labor, 2006). And, with expanding rates of urbanization, more people live in areas that are further removed from natural environments (Van den Berg et al., 2010), and access to green space is an important consideration for human development.
Many of studies have focused on benefits in terms of stress reduction and recovery from mental fatigue. Dr. Rita Berto defined “stress” in her literature review of the role that nature plays in coping with stress (2014):
“Stress” can be defined as the condition that results when person-environment transactions lead the individual to perceive a discrepancy (whether real or not) between the demands of a situation and the biological, psychological or social resources of the individual [1]. The negative effects of stress can be measured in various ways inside and out of the laboratory and these measures fall into three categories: those that rely on (1) neuro-physiological or bodily changes in the individual experiencing stress, (2) performance or behavioral changes and (3) self-report by individuals.
As you will read in the following section, researchers have attempted to measure the benefits of green nature in many different ways, from proximity of trees, gardens, and natural areas to view from a window.
Access to Green Space
Spending time with living, green plants in natural settings, viewing them from a window, or just living near green areas is associated with reducing stress and recovery from mental fatigue (Abraham et al., 2010; Carrus et al., 2015; Watts, 2017; Wolf & Housley, 2014). Access to nature is related to happiness. One study found that after controlling for other variables, access to nature is related to several indicators of happiness (Zelenski & Nisbet, 2014). In fact, more accessibility to parks and natural, forest-like environments is related to increased happiness, better concentration, and less stress, anger, depression, and tension (Van den berg et al., 2003).
Access to green space can also improve memory retention. One experiment tested the working memory of participants who either walked through an arboretum or who walked along a busy urban street. Those who walked through the arboretum had a 20% greater improvement in working memory than those who walked on the urban street (Berman et al., 2012). Another similar study found that those who went on a 50-minute walk in green nature had better working memory and less anxiety than participants who went on a 50-minute walk on a busy street (Berman et al., 2012).
As tree canopy in a community increases, crime tends to decrease. One study found that a 10% increase in tree cover is related to a 12% decrease in crime (Troy et al., 2012).
In the Workplace
A view of nature is also related to satisfaction with work and life. A longitudinal study of employees over a 6-month period found that individuals who had a view of nature in their workspace were more satisfied with their jobs than individuals who did not have a view of nature (Kaplan, 1983). Another survey found that of 615 office workers, individuals with a view of nature were more satisfied with their lives and were more enthusiastic with their jobs than workers who did not have a view of nature (Kaplan, 1983). Workers who have a view of green nature are more productive, have higher workplace satisfaction, and tend to be happier than those who do not (Lottrup et al., 2015).
Interior plants in the workplace (Figure 9.5.4) are associated with increased productivity, decreased stress, improved attention, and higher rates of workplace satisfaction (Gilchrist et al., 2015, Hartig et al., 2014, Raanaas et al., 2011). One study found that the presence of green plants in the workplace increased worker productivity by 15% (Korpela et al., 2017; Nieuwenhuis et al., 2014). Researchers found that as few as three small to medium sized plants can positively impact reaction time and perceived air quality and that as the number of plants in a room increased, so did the mood of the study participants (Lee & Maheswaran, 2011).
In Schools
Living plants in the classroom can improve student performance and influence classroom evaluations. One study found that when plants were placed in a classroom, students advanced through the curriculum 20 to 26% times more quickly (van Duijin et al. 2011). Students who have a view of green space during school have better attentional capacity and lower stress (Kuo, 2015; Becker et al., 2017), or are better able to recover from stress (Li & Sullivan, 2016). A view of green space from the classroom may also be related to academic achievement (Benfield et al., 2015; Browning & Rigolon, 2019). Even the amount of green space on a playground can impact students in the classroom. Students who play in areas with high levels of green nature tend to experience less physiological stress and have improved psychological well-being when compared to children who play in areas with low levels of green space (Kelz et al., 2015)
Students who are diagnosed with attention disorders such as ADD and ADHD may benefit from time spent in nature. One study found that children who have ADHD concentrated better after a walk through the park when compared to children who walked through a downtown neighborhood (Taylor & Kuo, 2009).
At Home
Plants and nature are related to neighborhood satisfaction. One study compared medical records of households in areas with different amounts of green space near their home. When compared to participants living in an area with the greatest amount of green space, those who had only 10% of green space within half a mile of their home had 30% more of a risk of developing anxiety disorders and 25% greater risk of depression (Wolf & Housley, 2014). Additionally, individuals that actively engage in gardening are more satisfied with their neighborhood than those who do not. One survey of apartment dwellers found that permitting gardening activities within or near a neighborhood increased resident satisfaction. In addition to the benefits from gardening, researchers found a strong positive correlation between merely having a view of nature from the home and residential satisfaction (Kaplan, 2001).
Access to nature may also be related to self-control. One study focused on a group of girls who lived in the same housing complex. The girls who had a better view of green space from their windows showed better discipline, concentration, impulsivity, and ability to delay gratification (Taylor et al., 2002). Furthermore, aggression and violence decrease for apartment residents who have access to nearby nature when compared to residents of apartments in a barren environment (Kuo & Sullivan, 2001). Adolescents who live in an area where green space is within 1000 meters of their residence exhibit less aggressive behavior than those without close access to nature (Younan et a., 2016).
Horticultural Therapy
In Green Nature Human Nature, Charles Lewis writes that the primary purpose of horticulture therapy is to “promote the wellbeing of individual patients, and plants become byproducts of the healing process.” Horticulture therapy has both physiological and psychological benefits to patients. The American Horticulture Therapy Association describes horticulture therapy as follows:
Horticultural therapy techniques are employed to assist participants to learn new skills or regain those that are lost. Horticultural therapy helps improve memory, cognitive abilities, task initiation, language skills, and socialization. In physical rehabilitation, horticultural therapy can help strengthen muscles and improve coordination, balance, and endurance. In vocational horticultural therapy settings, people learn to work independently, problem solve, and follow directions. Horticultural therapists are professionals with specific education, training, and credentials in the use of horticulture for therapy and rehabilitation.
Participation in horticulture therapy programs has been found to help people cope with post-traumatic stress disorder (PTSD) (Figure 9.5.5). Veterans with post-traumatic stress who participate in Nature Adventure Rehabilitation report feeling more hope for the future as well as improvements in emotional and social quality of life (Gelkopf et al., 2013). Victims of natural disasters are also at high risk of PTSD. Nature disaster victims who participated in a horticulture therapy program showed fewer symptoms of the disorder than victims who participated in a standard stress-education program (Kotozaki et al., 2015; Sekiguchi et al., 2015).
Researchers have found that horticulture therapy can reduce the effects of dementia by improving cognitive capacity and reducing instances of aggressive behavior (Gigliotti & Jarrott, 2005).
Physiological Benefits of Plants
Spending time with green nature not only benefits our mental wellbeing, but our physical health as well. As with the psychological benefits of plants, several studies have explored the relationship between access to green space and physiological health.
Access to Green Space
People who have access to green space tend to experience less stress and engage in more physical activity (Thompson et al., 2012). Access to green space can improve sleep quality and duration (Astell-Burt et al., 2013; Morita et al., 2011), which is important because insufficient sleep is associated with serious, chronic health issues (Cappuccio et al., 2011; Cappuccio et al., 2008; Chaput et al., 2007; Hislop & Arber, 2003; Hublin et al., 2007). Exposure to plants can also positively impact diabetes by increasing anti-diabetic hormones adiponecitin and didehydroepiandrosterone (DHEA) (Bhasin et al., 2013; Ohtsuka, 1998).
Access to Trees
The number of trees, amount of tree canopy, and access to trees can impact health (Figure 9.5.6). One study found that people who live in neighborhoods with a high density of street trees tend to report significantly fewer cardio-metabolic health conditions (Kardan et al., 2015). The same study also found that having an average of 11 more trees on a city block, on average, has cardio-metabolic health benefits usually associated with an increase of $20,000 in personal income and moving to a neighborhood that has a $20,000 higher median income or being 1.4 years younger (Kardan et al., 2015).
The city of Portland, Oregon explored the health benefits associated with trees. They found that when trees improve air quality by reducing the amount of NO2, the healthcare benefits from fewer respiratory problems are estimated at $7 million (Rao et al., 2014).
Researchers have attempted to gauge whether the loss of trees would have an impact on human mortality. After controlling for many other factors that could impact mortality, communities where trees have been lost to the emerald ash borer (an invasive insect pest) have experienced a corresponding increase in mortality related to lower-respiratory-tract and cardiovascular illnesses. For the 15 states included in the study, tree loss due to the emerald ash borer was linked with 6,113 lower-respiratory-system related deaths and 15,080 deaths related to cardiovascular health problems (Donovan et al., 2013). The implication of this study is that trees are associated with cardiovascular and lower-respiratory-tract health, and the loss of trees is connected with mortality due to cardiovascular and respiratory illnesses.
Access to Gardening
Participation in hands-on gardening activities is linked to physical health. Gardening is exercise. Digging holes for planting, pushing mulch in a wheelbarrow, raking leaves, pulling a hose or carrying a watering can are just a few examples of physical activities common to gardening.
Edible gardening is related to fruit and vegetable consumption. One study found that while non-gardeners only ate fruits and vegetables on average 3.9 times per day, home gardeners consumed produce 4.6 times per day and community gardeners 4.6 times per day (Litt et al., 2011).
Horticulture Therapy
Horticulture therapy can be used to improve coordination and strengthen muscles. One study followed a group of elderly women who participated in a 15-week gardening program and found that participants had an improvement in dexterity and muscle mass and a decrease in waist circumference when compared to an indoor control group (Park et al., 2016).
Horticulture therapy has also been used to help people manage chronic musculoskeletal pain. Participants were less dependent on pain medication, exhibited better coping skills, and had better mental and physical health (Verra et al., 2012).
In Hospitals
Hospital patients who have a view of green nature from their window tend to recover from surgery more quickly and require less pain medication (Mehaffy & Salingaros, 2015; Park et al., 2013). They also are more likely to have more positive interactions with hospital staff (Ulrich, 1983). Hospital patients who have living plants in their rooms or posters of plants may also experience less stress (Beukeboom et al., 2012)
In Schools
The CDC encourages schools to provide farm-to-school activities that provide hands-on education through school garden programs and field trips to local farms, classroom nutrition education, and alternative fundraising using local produce (Harmon, 2011). School garden programs (Figure 9.5.7) have the potential to strengthen the healthy development of students through improved knowledge about fruits and vegetables, increased preference for fruits and vegetables (Morris & Zidenberg-Cherr, 2002; Parmer et al., 2009; Robinson-Obrien et al., 2009), and increased consumption of fruits and vegetables (McAlleese & Rankin, 2007; Parmer et al., 2009; Robinson-Obrien et al., 2009; Ozer, 2007). Children who play in natural environments tend to develop better balance and coordination, which are predictors of physical activity (Fjørtoft, 2001; Fjørtoft, 2004).
Medicinal Benefits of Plants
In addition to providing food, textile fiber, building material, physical exercise, psychological benefits, plants have been used as a source of medicine for most of human history. Even today, researchers and pharmaceutical companies are searching for plants for medicinal properties, and many people grow herbs in their gardens for basic remedies.
How Long Have People Been Using Medicinal Plants?
Excerpt from "Medicinal Botany" by the USDA Forest Service is in the Public Domain
Our earliest human ancestors found plants to heal wounds, cure diseases, and ease troubled minds. People on all continents have long used hundreds, if not thousands, of indigenous plants, for treatment of various ailments dating back to prehistory. Knowledge about the healing properties or poisonous effects of plants, mineral salts, and herbs accumulated from these earliest times to provide health and predates all other medical treatment.
Evidence exists that plants were used for medicinal purposes some 60,000 years ago. A burial site of a Neanderthal man was uncovered in 1960. Eight species of plants had been buried with him, some of which are still used for medicinal purposes today.
By 3500 BC, Ancient Egyptians began to associate less magic with the treatment of disease, and by 2700 BC the Chinese had started to use herbs in a more scientific sense. Egyptians recorded their knowledge of illnesses and cures on temple walls and in the Ebers papyrus (1550 BC), which contains over 700 medicinal formulas.
Hippocrates, 460 – 380 BC, known as the “Father of Medicine,” classified herbs into their essential qualities of hot and cold, moist and dry, and developed a system of diagnosis and prognosis using herbs. The number of effective medicinal plants he discussed was between 300 and 400 species.
Aristotle, the philosopher, also compiled a list of medicinal plants. His best student, Theophrastus discussed herbs as medicines, the kinds and parts of plants used, collection methods, and effects on humans and animals. He started the science of botany with detailed descriptions of medicinal plants growing in the botanical gardens in Athens.
The most significant contribution to the medicinal plant descriptions was made by Dioscorides. While serving as a Roman army physician, he wrote De Materia Medica in about AD 60. This five-volume work is a compilation concerning approximately 500 plants and describes the preparation of about 1000 simple drugs. Written in Greek, it contains good descriptions of plants giving their origins and medical virtues and remained the standard text for 1,500 years.
The earliest Ayurvedic texts on medicine from India date from about 2,500 BC. In Ayurvedic theory, illness is seen in terms of imbalance, with herbs and dietary controls used to restore equilibrium. Abdullah Ben Ahmad Al Bitar (1021 – 1080 AD) an Arabic botanist and pharmaceutical scientist, wrote the Explanation of Dioscorides Book on Herbs. Later, his book, The Glossary of Drugs and Food Vocabulary, contained the names of 1,400 drugs. The drugs were listed by name in alphabetical order in Arabic, Greek, Persian, or Spanish.
Galen, a physician considered the “medical pope” of the Middle Ages, wrote extensively about the body’s four “humors”—the four fluids that were thought to permeate the body and influence its health. Drugs developed by Galen were made from herbs that he collected from all over the world.
The studies of botany and medicine became very closely linked during the Middle Ages. Virtually all reading and writing were carried out in monasteries. Monks laboriously copied and compiled the manuscripts. Following the format of Greek botanical compilations, the monks prepared herbals that described identification and preparation of plants with reported medicinal characteristics. At this time though, healing was as much a matter of prayer as medicine. Early herbalists frequently combined religious incantations with herbal remedies believing that with “God’s help” the patient would be cured.
With time, practitioners began to focus on healing skills and medicines. By the 1530s, Paracelsus (born Philippus Theophrasts Bombastus von Hohenheim, near Zurich in 1493), was changing Europe’s attitudes toward health care. Many physicians and apothecaries were dishonest and took advantage from those they should be helping. Paracelsus was a physician and alchemist who believed that medicine should be simple and straight forward. He was greatly inspired by the Doctrine of Signatures, which maintained that the outward appearance of a plant gave an indication of the problems it would cure. The Doctrine of Signatures is evident in many common names of plants today. For example, lungwort (Pulmonaria spp.) was once used to treat respiratory illnesses because its leaves somewhat resemble human lungs.
In 1775, Dr. William Withering was treating a patient with severe dropsy caused by heart failure. He was unable to bring about any improvement with traditional medicines. The patient’s family administered an herbal brew based on an old family recipe and the patient started to recover. Dr. Withering experimented with the herbs contained in the recipe and identified foxglove (Digitalis purpurea) as the most significant. In 1785, he published his Account of the Foxglove and Some of Its Medical Uses. He detailed 200 cases where foxglove had successfully been used to treat dropsy and heart failure along with his research on the parts of the plant and harvest dates that produced the strongest effect. Withering also realized that therapeutic dose of foxglove is very close to the toxic level where side effects develop. After further analysis, the cardiac glycosides digoxin and digitoxin were eventually extracted. These are still used in treating heart conditions today.
In 1803, morphine became one of the first drugs to be isolated from a plant. It was identified by Frederich Serturner in Germany. He was able to extract white crystal from crude opium poppy. Scientists soon used similar techniques to produce aconitine from monkshood, emetine from ipecacuanha, atropine from deadly nightshade, and quinine from Peruvian bark.
In 1852, scientists were able to synthesize salicin, an active ingredient in willow bark, for the first time. By 1899, the drug company Bayer, modified salicin into a milder form of aectylsalicylic acid and lauched asprin into our modern world.
The synthetic age was born and in the following 100 years, plant extracts have filled pharmacy shelves. Although many medicines have been produced from plant extracts, chemists sometimes find that the synthetic versions do not carry the same therapeutic effects or may have negative side effects not found when using the whole plant source.
A full 40 percent of the drugs behind the pharmacist’s counter in the Western world are derived from plants that people have used for centuries, including the top 20 best-selling prescription drugs in the United States today. For example, quinine extracted from the bark of the South American cinchona tree (Cinchona calisaya) relieves malaria, and licorice root (Glycyrrhiza glabra) has been an ingredient in cough drops for more than 3,500 years. The species native to the United States, Glycyrrhiza lepidota, has a broad range from western Ontario to Washington, south to Texas, Mexico and Missouri. Eastward, there are scattered populations. The leaves and roots have been used for treating sores on the backs of horses, toothaches, and fever in children, sore throats and cough.
Medicinal interest in mints dates from at least the first century A.D., when it was recorded by the Roman naturalist Pliny. In Elizabethan times more than 40 ailments were reported to be remedied by mints. The foremost use of mints today in both home remedies and in pharmaceutical preparations is to relieve the stomach and intestinal gas that is often caused by certain foods.
Modern Ethnobotany
Most United States residents have easy access to pharmacies that are fully stocked with neatly labelled bottles of uniform pills and syrups; therefore, it can be difficult to appreciate the role plants and other natural materials continue to play in modern medicine.
Ethnobotanists like Dr. Cassandra Quave of Emory University are modern-day plant hunters who work hard to identify, test, and introduce new plant-based medicines. In her book The Plant Hunter, Dr. Quave writes “Of the estimated 374,000 species of plants on earth, records exist for the medicinal use of at least 33,443[...] That means that around 9% of all plants on earth have been – and in many cases, continue to be – used as a major form of medicine for people.” Yet of the estimated 9% of plants with medicinal value, fewer than 5% have been studied in a lab.
That’s where ethnobotanists come in. They begin by interviewing people who have traditional knowledge of medicinal plants that grow in their region or reading historic accounts of plants that have healing properties. These scientists work with indigenous community members to identify and collect the correct species of plants. According to Dr. Quave,
As of January 2021, the global population is 7.8 billion people, and roughly 80 percent of them, or 6.2 billion, live in economically underdeveloped countries. Medicinal plants constitute the primary pharmacopoeia, or primary form of medicine, for 70-95 percent of people living in most developing countries. In other words, at least 4 billion people are dependent on plants for medicine, and the key ingredients in their medicine chests are getting more and more difficult to find.
Once the plants have been identified and collected, a portion of the samples are preserved in an herbarium. An herbarium is a library of preserved plant specimens that have been dried, pressed, and labelled with information about where they were collected. Herbarium specimens are an important reference for research, education, and identification.
The remainder of the samples are transported to a lab, where they are processed as ground and dried material or as liquid extracts. These samples are tested to determine their chemical and molecular composition. Samples are tested for their efficacy in combating various bacterial, fungal, and viral diseases. Doctors and pharmaceutical companies learn the results of these studies when they are published and presented at conferences. A new medicine can be introduced after further testing and product development.
Even once a new medicine has been identified and introduced, the search is far from over. Over time and with increased exposure, the organisms responsible for diseases can adapt and become resistant to tried-and-true treatments. Identifying medicinal plants is becoming more difficult, both due to loss of information and habitat destruction. Traditionally, older members of the community would pass these traditions to the younger members; however, this knowledge is at risk of being lost forever as young members of these communities move away in search of better opportunities and as older members grow in age. Even if these traditions are recorded, the native ranges of medicinal plants around the world are threatened by human development. The race is on for ethnobotanists to preserve both the records of plants used and the genetic information of the plants themselves. Investments in research and nature conservation are the keys to ensure our health now and in the future.
Dig Deeper
For more information about the role plants play on human wellbeing, check out Dr. Charles Hall and Dr. Melinda Knuth's comprehensive series of literature reviews on the benefits of plants and horticulture that were published in the Journal of Environmental Horticulture:
- 1: A Review of the Emotional and Mental Health Benefits of Plants
- 2: Physiological Health Benefits
- 3: Social Benefits
- 4: Available Resources and Usage of Plant Benefits Information
To learn more about the importance of nature to children’s development, check out the Children and Nature Network website.
To learn more about modern plant hunters and the search for new plant-based medicines, check out Dr. Cassandra Quave’s TeachEthnobotany YouTube Channel
To learn more about the field of ethnobiology, visit the International Center of Ethnobiology website.
Attribution and References
Attribution
Excerpt from "Medicinal Botany" by the USDA Forest Service is in the Public Domain
Title image: "Appalachian Trail, Smoky Mountain National Park, TN" by Abhishek Chinchalkar is marked with CC BY-NC-ND 2.0.
References
Abraham, A., K. Sommerhalder & T. Abel. (2010). Landscape and well-being: a scoping study on the health-promoting impact of outdoor environments. International Journal of Public Health, 55(1): 59–69.
Astell-Burt, T., Feng, X., & Kolt, G. S. (2013). Does access to neighbourhood green space promote a healthy duration of sleep? Novel findings from a cross-sectional study of 259 319 Australians. BMJ Open, 3(8), e003094–. https://doi.org/10.1136/bmjopen-2013-003094
Berman, M.G., Kross, E., Krpan, K. M., Askren, M. K., Burson, A., Deldin, P. J., Kaplan, S., Sherdell, L., Gotlib, I. H., & Jonides, J. (2012). Interacting with nature improves cognition and affect for individuals with depression. Journal of Affective Disorders, 140(3), 300–305. https://doi.org/10.1016/j.jad.2012.03.012
Becker, C., Lauterbach, G., Spengler, S., Dettweiler, U., & Mess, F. (2017). Effects of Regular Classes in Outdoor Education Settings: A Systematic Review on Students’ Learning, Social and Health Dimensions. International Journal of Environmental Research and Public Health, 14(5), 485–. https://doi.org/10.3390/ijerph14050485
Benfield, J.A., Rainbolt, G. N., Bell, P. A., & Donovan, G. H. (2015). Classrooms With Nature Views: Evidence of Differing Student Perceptions and Behaviors. Environment and Behavior, 47(2), 140–157. https://doi.org/10.1177/0013916513499583
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