Loss of World's Top Predators Is Pervasively Changing Ecosystems

coral reef sharks — A healthy coral reef ecosystem with sharks off Jarvis Island, an uninhabited island located in the South Pacific Ocean. A loss of these large predators can alter the patterns of predation and herbivory, ultimately leading to an coral system where reef-building corals and coralline algae lose their competitive advantage.

(Image credit: Brian Zgliczynski)

The loss of top predators, such as lions, wolves and sharks, is causing unpredictable changes to food chains around the world, according to a review written by 24 scientists.

These animals, called apex predators, play a crucial role in ecosystems, and their disappearance — often due to hunting by humans and loss of habitat — can lead to changes in vegetation, wildfire frequency, infectious diseases, invasive species, water quality and nutrient cycles, according to the authors led by James Estes, a professor of ecology and evolutionary biology at the University of California, Santa Cruz.

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The loss of these predators at the top of the food chain causes a cascade of effects down the line. The authors cite many examples, such as the decimation of wolves, which have since been reintroduced in Yellowstone National Park, led to over-browsing of vegetation by elk. The loss of lions and leopards in parts of Africa has led to changes in olive baboon populations and increased their contact with humans, which, in turn, has caused higher rates of intestinal parasites in both people and baboons. [Gallery: The World's Biggest Beasts]

Wynne was a reporter at The Stamford Advocate. She has interned at Discover magazine and has freelanced for The New York Times and Scientific American's web site. She has a masters in journalism from Columbia University and a bachelor's degree in biology from the University of Utah.