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A Comparison of the Abundance of Selected Medicinal Plants in Primary Forest, Secondary Forest and Pasture/Roadside at Palo Verde National Park, Costa Rica.

Authors:

Gabriell DeBear Paye, West Roxbury High School, Boston, MA

John Neering, Pelham Memorial,High School, Westchester County, NY

Giselle Nakhid, John Jay High School, Brooklyn, NY

Meenamba Hass, Satellite Academy High School, New York, NY

Abstract

Focusing on the intersection between humans and nature, this investigation combines ethnobotanical qualitative research with field transects to give an overall view of the use and abundance of 4 different medicinal plants of Palo Verde National Park in 3 different habitats: primary forest, secondary forest, and pasture/roadside. The species studied were: Berengena (Solanum verrogeneum), Arnica (Trixis inula), Naked Indian (Bulsera simaruba), and Horse Testicles (Stemmadenia obovata). The medicinal herbaceous plants were more abundant in the pasture/roadside areas, and the medicinal trees were more abundant in the primary and secondary forests as per our hypothesis. These findings have serious implications on land use management policies in tropical dry forest regions such as Palo Verde, and will be discussed in this paper.

Introduction

Through the years, plants have been the primary source of drugs used to treat illnesses. The majority of this kind of treatment consists of plant-based medicines. These were first discovered by first studying their uses in folk medicine. There is a close relationship between plants and medicine. This investigation focuses on the medicinal properties of several selected plants in the tropical dry forest at Palo Verde National Park.

Two species of herbaceous plants, and two species of trees that are known locally for their medicinal value were studied. The herbaceous plants included Berengena (Solanum verrogeneum), and Arnica (Trixis inula). The two trees selected for this study were Naked Indian (Bulsera simaruba), and Horse Testicles (Stemmadenia obovata).

Berengena (Solanum verrogeneum):

Berengena has fuzzy leaves that resemble the leaf of the eggplant, from which its common name in Spanish is derived. Like the eggplant, it is in the Solanaceae family. The stems have sharp spines. The flowers are white and the fruit is green and hairy. It is used by local people to treat kidney ailments, such as kidney stones and nephritis. It is prepared by digging up the root, boiling it, and drinking it. (Torre Carrillo, and Chaverria Garcia, pers.com).

Arnica (Trixis inula):

Arnica is used locally and internationally amongst practitioners of alternative/homeopathic medicine to treat muscle aches and external inflammations due to bumps and scrapes. Either an extract or a poultice of the leaves can be applied to the inflamed area (Jose pers. com.)

Naked Indian (Bulsera simaruba):

The Naked Indian plant has a distinctive orange bark which peels off to reveal a green photosynthesizing bark underneath. The leaves are pinnately compound. It is used to treat gastritis, anemia, and chagas (a disease is caused by a parasite which is passed by the triatomid or “kissing bug” that results in severe damage to the heart). It has also been used as an insecticide, for diarrhea, indigestion, obesity, anemia and chagas disease.

Horse Testicles (Stemmadenia obovata):

This tree has a smooth, pale whitish bark with prominent lenticils. The leaves are simple and glossy. The fruit is green and is paired (resembling its common name “horse testicles”). The sap is used to treat boils, and it is considered a better remedy than nail polish for the removal of botfly larvae under the skin (a common ailment in Costa Rica).

Hypothesis

Based on preliminary research and observations, it is expected that the medicinal trees will be found in more abundance in the primary and secondary forests, and that the herbaceous medicinals will be found in more abundance in the pasture/roadside.

Materials and Methods

Initial interviews and instructional walks were conducted with local people, including park ecologists to compile a list of plants and trees of medicinal value. From there, the broad list was narrowed down to the four above-mentioned species, using the following criteria: apparent abundance of the species at Palo Verde, facility of identification, medicinal value to local people, and availability of background information.

Ulises Chavarria Garcia is a plant taxonomist at the

Palo Verde National Park, Costa Rica.

The pasture/roadside site is located approximately 2 km from the Tempisque River, next to the access road. The secondary forest site is located behind the OTS station on an intermediate slope. The primary forest site is located approximately 2 km from the Tempisque River on a steep slope. At each site a transect measuring 50 m. was made. We measured plants within one meter of either side of the transect, so that a total of 100 square meters was surveyed at each site. An inventory of the amount of herbaceous plants and trees was taken. The Diameter at Breast Height (DBH) of each tree, and the height of each herbaceous plant was measured.

Results

See Appendix #1 for detailed raw data.

Discussion

As predicted in our hypothesis, there were no medicinal tree species in the pasture/roadside site. And there were none of the targeted herbaceous medicinal species at either the primary or secondary forest sites.

One unexpected result was that all of our selected species were site specific. In other words, each species was found in only one habitat type in the plots that we surveyed. The herbaceous plants namely the Arnica and Solanum were found only at the pasture/roadside site. The Naked Indian was only found at the secondary forest site. It was clustered in the first 20 meters of our transect where limestone was visibly abundant. We had been informed that these trees thrive in a limestone rich habitat (Turner Mojica, Nicole). We found the Horse Testicle trees only in the primary forest site. We would be curious to see if this trend would hold up with more extensive research at the three sites.

Another unexpected finding in this study was the incredible abundance of a particular medicinal plant that we chose not to include in the study, namely the wild yam (Dioscoria villosa) which was found in the primary forest. In the primary forest plot of 100 square meters, 76 plants of this variety were found. We only found 3 of them in the secondary forest. This plant has been used in the past as a form of contraception, and is currently being prescribed by many traditional and alternative health practitioners as a natural hormone replacement therapy for menopausal women. This finding leads to the question of whether primary forest is the only habitat that can support this important medicinal plant species.

Wild Yam, Dioscorea villosa

It was apparent that some of the medicinal plants that we studied were more abundant than others. We found 13 specimens of the Solanum verses only 2 Arnica on the roadside/pasture site. In the forest sites we found 14 Horse Testicle trees compared to only 6 specimens of the Naked Indian tree. Before utilizing plants medicinally and/or harvesting and marketing them, a thorough study as to their abundance and rates of growth and regeneration should be made to insure that the selected plants do not become in danger of extinction due to overuse. Sustainable use studies should be conducted on promising medicinal plants.

Based on our limited study, these findings could have serious implications on biodiversity in the tropical dry forest. It appears that many species are endemic (meaning that they are found only in a certain place) to a particular habitat. It appears that the 4 species that we studied thrive under specific environmental conditions and would be adversely affected by loss of habitat due to human intervention or human impact.

As deforestation continues to threaten the integrity of our ecosystems, it is clear that much is being lost in terms of plants that could be used medicinally.

Classroom Applications

This type of inquiry based project can be facilitated at all levels, from grades 4-12, in curriculum designed for both AP and “regular” classes. It lends itself to a myriad of subject areas within science, such as: chemistry, biology, ecology, environmental science, botany, and more. It has strong interdisciplinary implications as well, since it also includes skills related to math, statistics, language arts, social studies, computer technology, and fine arts. For example, this project involved graphing, computer literacy, data collection and analysis, interviewing, public speaking, primary and secondary research, writing, and learning about other cultures. Though this project was conducted in the dry tropical forest of Costa Rica, the process used to carry it out would translate well to a variety of environments ,and school settings outside of Costa Rica. In addition, projects such as this one, address a large spectrum of learning styles, and encourages student involvement, as they choose the topic on which the project is based.

For further ideas on this type of activity see Cultural Uses of Plants, a curriculum by Gabriell.

References

Chavarria Garcia, Ulises,Plant Taxonomist, Palo Verde National Park, Costa Rica. Personal communication 7/24/00

Gupta, Mahabir P., Ph.D. 270 Plantas Medicinales Iberoamericanas. Bogota, Colombia: Convenio Andres Bello, 1995

Torre Carrillo, Jose, Park Management, Palo Verde National Park, Costa Rica. Personal communication, 7/25/00

Turner Mojica, Nicole, Tropical Biologist, , Palo Verde National Park, Costa Rica. Personal communication, 7/25/00

Paye, Gabriell De Bear. Cultural Uses of Plants. A Guide to Learning About Ethnobotany New York Botanical Garden Press. Bronx, NY 2000

Ramirez, Osvaldo Perez. El Prodigio Corativo de las Plantas. Naturismo Centroamericano Presenta 1995

Chavez, Gloriana and Montiel, Viviana, Kitchen Staff. Palo Verde National Park, Costa Rica. Personal communication, 7/24/00

Medicinal Plant Group with Palo Verde Kitchen Staff. From left to

right is : Meenamba, Giselle, Viviana, John, Gloriana and Gabriell.

Appendix #1: Raw Data Table.

Primary Forest
Solanum	0	0	0	0	0
Arnica	0	0	0	0	0
Naked Indian	0	0	0	0	0
Horse testicles	3 specimens	2 specimens	4 specimens	2 specimens	3 specimens
Average DBH	6.5 cm DBH	7.3 cm. DBH	5.2 cm. DBH	6.8 cm. DBH	7.1 cm. DBH
Secondary Forest
Solanum	0	0	0	0	0
Arnica	0	0	0	0	0
Naked Indian	3	3	0	0	0
Average DBH	28 cm DBH	24 cm. DBH
Horse testicles	0	0	0	0	0
Altered Area
Solanum	1 specimen	0	4 specimens	8 specimens	0
Average height	1.5 m		2 m. average	1.8 m av.
Arnica	1 specimen	1 specimen	0	0	0
Average height	1.2 m	1 m.
Naked Indian	0	0	0	0	0
Horse testicles	0	0	0	0	0

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