Biodiversity protects ecosystems against infectious diseases, researchers have concluded. The finding suggests that loss of species from an environment could have dangerous consequences for the spread and incidence of infections, including those that affect humans. Felicia Keesing, a biologist at Bard College in Annandale, New York, and her colleagues reviewed several dozen studies published in the past five years and found that the link holds true across various ecosystems, pathogens and hosts. “A pattern is emerging which shows that biodiversity loss increases disease transmission,” says Keesing, whose study is published today in Nature1.
The researchers don't know why the effect occurs. But they speculate that species that are better at buffering disease transmission — for example because they have low rates of reproduction or invest heavily in immunity — tend to die out first when diversity declines, whereas species that have high rates of reproduction or invest less in immunity — and thus are more likely to be disease hosts — survive for longer.