Biodiversity and Health – An International Perspective from A Duke Med Student

Published April 6, 2008 under Research News

As medical students at Duke, we are encouraged to challenge assumptions and break beyond the confines of the medical amphitheatre to pave our own paths into healthcare. 

This February, supported by a grant from the Duke Medical School Multicultural Resource Center, I traveled to the Second International Conference on Health and Biodiversity (COHAB 2) in Galway, Ireland.  Attended by ecologists, veterinarians, medical doctors, public health specialists, UN delegates and government officials from six continents, the conference served as a forum to discuss the value of biodiversity and the implications of its loss on global health.  In culmination, the conference authored the Galway Declaration – a brief document to inform future policy and funding decisions.

Biodiversity, when considered globally, comprises the whole of the plant and animal kingdoms from the tiniest ocean floor microbes to the largest land mammals.  It includes a near unimaginable variety of species that create a web of mutually dependent and supportive living organisms.  When considered locally, the same structure applies –only the web is much smaller, and so any disruption or imbalance of one supporting species has a considerably magnified effect.  In our era of exponential human population growth, globalization, and environmental impact, we are significantly changing the balance and distribution of this web.  Humanity, though often considered as an entity distinct from the realm of the wild plant and animal, is in fact linked with an incalculable number of other species – the indiscriminate destruction of which is having very real and quantifiable effects on our own survival.

As such, preserving biodiversity and healthy ecosystems is very much in our best interest.  Serving to clarify these benefits, the Galway conference was organized into three subgroups, each focusing on one area in which biodiversity has direct application to humanity and health:

1. The prevention and mitigation of disaster impacts and enabling of faster and more comprehensive recoveries
2. The provision of food resources and contribution to nutrition
3. Decreasing the incidence and impact of emerging infectious diseases (EIDs)

As a medical student, the connection between biodiversity and infectious diseases is particularly resonant, and so I spent the majority of my conference time within the EID workshop. 

As forms of life themselves, the bacteria, microbes, and viruses that cause infectious diseases in humans can also be considered under the umbrella of biodiversity. Infectious diseases, in a sense, provide an important check on plant and animal health. Unfortunately, given the right circumstance they will thrive and overstep their role as contributive regulators of sustainable ecosystems. 
Human development often does not specifically target one species; rather it has wide reaching effects on a geographic area and as a result, can negatively impact many species, ultimately decreasing the biodiversity and overall health and function of the constituent ecosystem. Greater biodiversity limits over-expression of infectious diseases by a phenomenon known as the Dilution Effect, which posits that an ecosystem that houses a greater number of species/hosts dilutes the potential for interaction between the pathogen and target host, thereby decreasing the incidence of infection.  Thus, diminishing biodiversity by the impact of deforestation, development, pollution, etc., increases the ability of infectious diseases to find hosts in animal populations that may eventually be transmitted to humans. 

Such diseases that are contracted from animals are referred to as zoonoses.  Zoonoses comprise more than 60% of all emerging diseases, e.g. avian influenza, rabies, and Mad Cow Disease.  As we decrease biodiversity, we create conditions that are more favorable for disease vectors and in effect, increase the potential for zoonotic transmission. 

Perhaps more disconcerting than the zoonoses that we know of are the ones that we do not; the ones we might expect to arise given the currently degenerating environmental conditions. Destruction of biodiversity and habitat often occurs concomitantly with increased human-animal interaction – either by way of human settlement in areas that were once exclusively wilderness or by virtue of displaced and desperate animals interacting with human populations in search of food and shelter.  Furthermore, once zoonoses are transmitted to human populations, they may mutate and gain human to human transmission capabilities.  Smallpox, AIDS, and influenza are such examples and are key illustrations of the threat of animal originated pathogens. 

Recent years have seen a gradual acceptance of the vast body of evidence supporting a changing global climate.  With regard to biodiversity and infectious diseases, there is substantial support that changing temperatures and weather patterns will disrupt ecosystems. These disruptions could impact human health: for example arctic migratory bird nesting and migration patterns disrupted by increasing temperatures could prolong exposure to infected poultry and potentially facilitate the spread of H5N1 (bird flu). Climate change could also increase the incidence and range of vectors, as seen in the recent appearance of chikungunya in Italy – a tropical disease typically found in lower latitudes of the Indian Ocean region. Climate change could also contribute to the loss of many species – a disadvantage in the sense that it contributes to the diminishment of the aforementioned Dilution Effect. 

Though the implications of biodiversity loss are immense, I was inspired by those at the conference who proposed solutions and presented experiences that can and should serve as models for global action.  On a governmental level, we heard from the senior environmental minister of Guyana who explained steps that his country has taken to safeguard biodiversity, protect health, and preserve their economy sustaining tourism industry – most notably by building an article into the constitution that requires a commitment to the environment from all Guyanese citizens.  On a local level, we heard from a Ugandan veterinarian who established a program that incorporates public health education, community empowerment, traditional healer training, and wildlife health in response to scabies and diarrheal outbreaks in the area gorilla population contracted from the nearby human community. 

Biodiversity loss is a problem that requires immediate attention from individuals in a number of fields to fully address its complexity and to work toward comprehensive solutions.  As a physician in training, I feel it is my responsibility to work toward safeguarding human health on any level (individual, community or global) and to work with and learn from experts in ecology, veterinary medicine, and public health to better understand and prepare for the threats facing our shared future.  Biodiversity loss is an issue so large that it has the potential to impact anyone, anywhere.  It is the foundation upon which all life rests, and if undercut, is not something we are ever likely to get back. 

Timmy is a first year medical student at Duke.  Prior to coming to Durham he worked as a bioethics research assistant at UCSF.  He holds a bachelor’s degree in biology from Tufts and a master’s degree in bioethics and religion from Harvard.

Conference Website: