Biodiversity and epidemics

Our planet is occupied by the most diverse ecosystems: deserts, polar zones, temperate forests, rain forests or coral reefs. In general, the closer to the equator, the more biodiversity in the ecosystems. And the more biodiversity, the more complex are the trophic relationships between its organisms. However, surely most ecosystems have some so-called “key” species, since their importance is very great in relation to their abundance. The sea otter (Enhydra lutris), with its predatory activity, keeps sea urchin populations at bay, and therefore prevents them from eating all the algae. Prairie Dogs (Cynomys) build a complex system of underground galleries that fluff up and drain the ground, offering shelter and breeding space to other species. The jaguar is a very versatile predator, capable of hunting more than 80 different species, consequently it has an important role in regulating populations. The beaver builds dikes that flood large areas of land and profoundly transform the landscape. If any one of these key species goes extinct, the ecosystem collapses. Sometimes this collapse directly affects our health. On the east coast of the United States there is an endemic disease called Lyme, which is transmitted by ticks, and can cause serious neuromuscular disorders and encephalopathies. Scientists have discovered that it is caused by a bacterium, which has the natural reservoir in mice and chipmunks. When the ecosystem is rich and diverse, predators such as fox, raccoon, coyote, opossum, or bobcat keep micro-mammal populations at bay and the tick has few hosts to get infected. But when the ecosystem fragments, the number of predators decreases, and therefore the mouse population increases. The more mice, the more infected ticks, and through their bites, the more Lyme disease.
An ecosystem could be represented with the Mikado game. Each stick would be the relationship between a pair of organisms: a predator and its prey, a herbivore and the plant, a host and the parasite… As humans extinct species, would be like if we were removing sticks from the Mikado, without knowing what importance each species has, with the risk that we eliminate a key species and the ecosystem collapses. As far as possible, we should keep ecosystems intact. Biodiversity is a guarantee of ecosystem stability, but also of human health.