Worldwide decline of big predators causes ecosystem disturbances

An international research group today published in Science a study into secondary ecological damage by a decline in ‘apex consumers’ on a global scale. Such predators include whales, sharks, lions, leopards and wolves. Their falling numbers may lead to dominance of single (herbivorous) species and vegetation and biodiversity loss in ecosystems.

The authors cite a range of examples where predator decline led to further ecosystem damage. The extirpation of wolves in Yellowstone National Park for instance led to over-browsing of aspen and willows by elk. Once the wolf population was restored, the vegetation too could recover.

The phenomenon is called ‘trophic cascade’ – cascading ecological damage moving down through lower levels of the food chain, much like damage at the base at the base of the food chain can lead to collapses higher up. It is such positive biodiversity feedbacks that play a key role in massive extinctions – and make it difficult to translate seemingly abstract environmental threats into quantitative extinction risks.

© Rolf Schuttenhelm |

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