In the web of life, predators and prey exchange carbon and water, and each act of eating slightly increases the universe's disorder. But the intrusion of disease turns this system into a giant seesaw. When a mid-level predator gets sick, its hunting abilities decline, and it becomes easy prey. Instead of extinction, numbers start to oscillate — the seesaw rocks, but doesn't tip over.
For apex predators, the same disease can be fatal: the seesaw flips, and the species vanishes. Meanwhile, the survival odds for mid-level links actually increase.
Understanding this fragile mechanics helps to dampen dangerous swings in time and preserve entire ecosystems.
In Yellowstone, after a wolf epizootic, deer multiplied so much that they trampled stream banks, and rivers changed their courses.
In the movie 'Outbreak' (1995), a virus affecting predators triggers a chain of events threatening the entire ecosystem — a similar scenario is modeled in the study.