Source: Wikipedia
This is the first in a series of posts for the American Public Health Association’s National Public Health Week.
Most of us associate biodiversity with images of tropical rain forests and coral reefs. While these ecological hot-spots are an important source of medications and global ecosystem services, biodiversity also plays a key role in neighborhoods across the US through regulating the spread of diseases such as Lyme disease. But how is that possible, you might ask, and what can you do about it?
Lyme disease affects hundreds of thousands of people across the US, with a greater concentration in the northeast. Recent decades have seen an explosion of urban sprawl across the northeast leading to decreased species diversity along with people living in close proximity to fragmented habitats. But how are these related?
The connection is explained succinctly in Sustaining Life: How Human Health Depends on Biodiversity:
“The Blacklegged Tick (Ixodes scapularis) is the vector of Lyme disease, as well as of several other pathogens in the eastern U.S., and the primary reservoir for Lyme disease in this region is a common rodent, the White-Footed Mouse (Peromyscus leucopus)…Mice live in many different habitats, from pristine old-growth forest to degraded woodlots, garden sheds, and even kitchens. Several studies have demonstrated that populations of White-Footed Mice become very concentrated in small forest fragments, probably due to the absence of other vertebrate species that prey upon, or compete with them (forest fragmentation…affects predators over prey disproportionately). As a consequence, tick populations in small forest fragments have many White-Footed Mice, but few other mammalian hosts on which to feed, resulting in a high proportion of the ticks being infected and able to infect people. In contrast, in more extensively forested areas, the combination of fewer White-Footed Mice and more abundant, alternative, reservoir-incompetent hosts (an incompetent reservoir for Lyme does not pass on the Lyme bacteria to ticks that bite them, or does so poorly) results in a lower proportion of the tick population being infected.”
This phenomenon is known as the Dilution Effect: As species richness declines there is a subsequent decrease in the “dilution” of host-species making Lyme disease easier to spread. As the authors note, the dilution effect is not unique to Lyme, the same mechanism also operates in Hantavirus and West Nile Virus and possibly many others. As sprawl-based development patterns spread to more areas of the planet, we can only expect to see an increase in the number of dilution effect diseases unleashed upon populations worldwide.
So how can you increase biodiversity in your community and thereby help protect the health of your family and neighbors?
Get involved with your local conservation commission and bring these dangers to their attention. Find ways to support local parks and nature preserves. Also, if you have a yard or garden, try to plant local species that help support wildlife. Most importantly: Education! If you are in college or school, talk to your professors about integrating awareness of biodiversity into curriculum. Thanks to the UN and various donors, Sustaining Life is available at a very affordable price and can serve as a great textbook without placing a great financial burden on students. In addition, local schools can serve as great sources of biodiversity through gardens and planting of local species on grounds. Often these locals are less expensive to maintain, requiring less water and fertilizer.
These are just some ideas…we’d love to hear from GP readers with their experiences and success stories.
