Some of the frog species used in the experiment: diversity prevents contagion

Intuition, mathematical models and field observations have suggested that loss of native vegetation and all of its associated organisms may promote the transmission of viruses, bacteria and other disease-causing agents. The problem is that other scientific studies have argued the opposite. A new experiment has now strengthened the first possibility—the greater the number of species, the lower the transmission rate of a disease—by showing that the transmission of a fungus that caused the extinction of amphibians in several countries was 66% lower among groups of frogs with greater species diversity, compared to groups with a single species.

“Diversity alone, regardless of species composition, deters disease transmission,” concludes biologist Carlos Guilherme Becker, a researcher at São Paulo State University (Unesp) at Rio Claro and principal investigator for the study. Biological richness, therefore, measured by the number of plant and animal species, seems to have a protective effect by hindering the transmission of disease-causing agents.

On the basis of this reasoning, we can associate the loss of native vegetation, along with the organisms it hosts, with the emergence of viral diseases such as those responsible for the AIDS epidemic in the 1990s and the present-day outbreaks of Ebola. The viruses that cause these diseases were initially found in natural reservoirs, the wild animals that the poorest inhabitants of Africa kill for food.  “Recent years have seen intensive deforestation and hunting in the countries with the largest number of Ebola cases at present,”  Becker says. Read more.