Loss of biological diversity threatens human health
The rapid loss of biological diversity is a major threat to human health, say researchers in the open access international health journal PLoS Medicine.
Andy Dobson (Princeton University) and colleagues cite the example of Lyme disease, which in eastern North America is transmitted to humans by a blacklegged tick harboring the Lyme bacterium.
The ticks feed on a variety of different vertebrates, including the white-footed mouse and the gray squirrel, each with a different probability of infecting the tick with the Lyme bacterium. Over 90% of ticks feeding on white-footed mice become infected compared with fewer than 15% feeding on gray squirrels, and so ticks harboring the Lyme bacterium are much more common in habitats with many mice than in habitats that harbor a diversity of other species.
These white-footed mice, say the researchers, are more common in small patches of forest. These patches, created by habitat loss and fragmentation of the remaining habitat into smaller subdivided areas, are too small to support the predators and competitors that typically keep mouse numbers down. The loss of species diversity means that the risk to humans of Lyme disease is high in small patches of forest.
Dobson and colleagues give other examples of how loss of biological diversity threatens human health, including West Nile virus, which is transmitted to humans by a range of mosquito species and which can replicate in a variety of bird species. Initial research, say the authors, suggests that cases of human West Nile virus infection are less common in areas with high bird diversity. The virus is particularly likely to replicate in house sparrows, house finches, American robins, blue jays, and grackles, all of which proliferate in heavily fragmented or otherwise degraded habitats.