Since I started as a PhD candidate in March 2012, I have read a lot about the relationship between biodiversity and disease. Actually, I am studying this relationship by looking at the effect of mammal diversity on Lyme disease risk in the Netherlands, where I define Lyme disease risk as a combination of the tick density and the percentage of infected ticks. If we go back in time, the current discussion about the effect of biodiversity on disease risk started about 10 years ago, with a number of publications by Richard Ostfeld and colleagues in which they proposed the dilution effect, which in short argues that disease risk increases when biodiversity decreases (I have to say here that Ostfeld and colleagues state it much more elaborate, as there are a number of criteria that have to be met before this statement is true). There has been a lot of debate about this, with people arguing both for and against the dilution effect. However, I recently noticed a paper published by an economist which drew my attention.
Bonds and colleagues argue (click here to read the full paper) that biodiversity is not only related to disease risk, but also to per capita income. This seems quite a bold statement only to increase the support for the protection of biodiversity, and perhaps it is, but it made me think. Bonds et al. argue that there is a strong link between the natural environment and economy, by pointing to the latitudinal gradient that is visible in all kinds of processes from animal body size, to biodiversity, human disease burden and economy. The relationship between economy and latitude could be caused by vector-borne and parasitic diseases (VBPDs), which are most common around the equator, and which are a major cause of morbidity and mortality in poor countries, influencing the economy in these countries.
In their analysis, they perform a multiple linear regression, where they show that biodiversity had a significant negative effect on VBPDs, when controlling for all other factors. Indicating that a loss in biodiversity would indeed increase disease risk. Furthermore, VBPDs had a significant negative effect on income, when controlling for all other factors. Could this mean that protecting biodiversity could increase or at least stabilize income in poor countries?
As the authors state, there are many complex mechanisms underlying diseases, and only by unraveling these, can we gain more insight into how things work, but it does make you think!