Why Top Predators Matter

From the Environmental Defense Fund comes a warning of imbalance in our global oceans: 

The dire straits facing sharks around the world is a major theme in many gloom and doom predictions about the fate of the oceans. And there is plenty of reason for worry. Many shark populations are estimated to be at less than 10% of original levels, with some species possibly in danger of extinction. This is bad news not only for sharks, but for the many cultures that rely on them for protein in their diets.

Ecologists, too, warn of the effects of the decline in shark species and other top predators on ocean ecosystems. Eliminating sharks may induce what scientists call “ecological cascades,” where one effect induces another, and so on through the living world. 

One example of that process is the rise in populations of certain rays –  key shark prey – in regions where shark populations have declined. If there are too many bottom feeding rays, that may threaten seagrass beds and the shellfish that inhabit them. Those seagrass beds also serve as nurseries for many other species. So losing sharks may seriously degrade marine ecosystems, which could threaten the human fisheries tied to them. In addition, sharks can help control populations of invasive and exotic species – a growing problem as ocean ecosystems change.