14 DAY TRIAL // A new scientific analysis, recently published in the journal Nature, concluded that loosing biodiversity in any kind of ecosystem, rises the risks of the transmission of infectious diseases in humans, other animals and plants.
Until now, it's been quite difficult to quantify this relationship between the emerging new diseases and the high rates of biodiversity decline.
For their analysis, the authors looked at three recent studies of mosquito-transmitted West Nile virus, for which several species of birds act as hosts, and all three of them concluded to a strong relationship between low bird diversity and high risk of transmission to humans in the US.
The researchers explain that bird communities with a low diversity are usually dominated by species that intensify the virus, thus “inducing high infection prevalence in mosquitoes and people, while communities with high avian diversity contain many species that are less competent hosts.”
However, Anna Jolles, a disease ecology specialist in the College of Veterinary Medicine at Oregon State University and one of the authors of the study, admitted that this tendency isn’t always the case, and that for new diseases, a higher diversity can provide a wider potential pool of hosts.
“Hotspots for novel disease emergence sometimes center around areas where growing human populations come in contact with lots of wild animal species,” she said.
“The more host species are around, the more pathogen species they will harbor, and the more opportunity for transmission to people.”
Nevertheless, the analysis published in Nature, gave overwhelming evidence that the loss of biodiversity is tied to increases in disease transmission, and the authors say that this pattern applies to all types of pathogens – including viruses, bacteria and fungi – and for many types of hosts – human, other animals or plants.
Jolles said that “in theory, the loss of biodiversity could increase or decrease transmission of disease,” and “certainly, having naturally high biodiversity should increase the potential pool of sources for new pathogens.
“But the evidence suggests that in most cases, biodiversity loss actually ramps up transmission of disease.
“Now we need to find out why.”
The researcher and her colleagues also looked at dozens of published, peer-reviewed studies, and concluded that the most eloquent examples for their conclusions were the West Nile virus, Lyme disease and hantavirus.
Felicia Keesing, an ecologist with Bard College in New York, and lead author of the Nature study, says “we knew of specific cases like West Nile virus and hantavirus in which declines of biodiversity increase the incidence of disease.
“But we’ve learned that the pattern is much more general.
“Biodiversity loss tends to increase pathogen transmission and infectious disease,” she adds.
Another thing highlighted by this study is the alarming decreasing biodiversity tendency, with extinction rates 100 to 1,000 times higher that before.
And since predictions say that in the next 50 years, species should dramatically disappear, “if there is one message we hope comes out with this paper, it is the clear need to conserve biodiversity to the greatest extent possible – because it may be our best insurance policy against infectious diseases,” Jolles said.
The National Science Foundation, the National Institutes of Health, and the US Environmental Protection Agency, funded a large part of this research.