Forests Can Protect Humans from Disease
A group of scientists published a study earlier this month in the Nature journal, citing mounting evidence that biodiversity loss frequently increases infectious disease transmission.
One of the primary authors, Felicia Keesing from Bard College, explained the general pattern to Science Daily: “biodiversity loss tends to increase pathogen transmission across a wide range of infectious disease systems.” Keesing has been following the ecology of Lyme disease in northeastern forests for several years, and she said that evidence is mounting about biodiversity and disease. For instance, an opossum can serve as a biological buffer between the Lyme bacterium and humans by picking and killing off ticks. Opossums are poor hosts for ticks, but mice are good hosts. As biodiversity is lost, opossums move away and mice remain.
The authors also cite the relationship of the mosquito-transmitted West Nile disease and low bird diversity, as well as the relationship of hantavirus and lower diversity of small mammals. There are three reasons the loss of biodiversity can affect the transmission of infectious diseases:
- The more diverse the number of intermediate hosts, the less likely that a specific host will be present that are dangerous to humans.
- In a more diverse community, it’s more likely that the disease will end up in an unsuitable intermediate host.
- Genetically diverse hosts are generally in better condition and more resistent to disease.
The authors conclude: ”despite remaining questions, connections between biodiversity and disease are now sufficiently clear to increase the urgency of local, regional, and global efforts to preserve natural ecosystems and the biodiversity they contain.”
At the very least, the relationship of biodiversity and epidemiology is a very direct example of a principle the Forest Service has been using during the development of a new forest planning rule: that people and the environment are inseparable and interdependent. The idea that forests are actually a safety net is a compelling argument for the maintenance and restoration of functioning and diverse ecosystems.