29 | March | 2007 | Stephen Leahy, International Environmental Journalist

Humans are the ultimate apex predator — we eat anything that moves and hardly anything wants to eat us.

Sharks got nothing on us.

So what does it mean in ecological terms when there are six billion+ apex predators roaming the planet?

Massive extinctions of other species for one thing as we munch our way down the food chain. As species decline, ecosystems unravel leading to more declines and maybe some blooms of things like weeds and jellyfish. And eventually (perhaps sooner than later) we run out of food and lose ecosystem services, both of which will contribute greatly to rapid increases in disease and death in humans.

That seems to be the logical and grim ecological prognosis.

However, like a car hurtling towards the edge of the cliff, we’re arguing about what CD to listen too instead of applying the brakes. [Or more likely, each of us is plugged into our own IPOD and oblivious to each other and anything else.]

I admit that writing about environmental issues can be depressing. I’m actually an optimist and believe we will jump on those brakes at the last minute.

As Sharks Vanish, Chaotic New Order Emerges
By Stephen Leahy

Mar 29 (IPS) – Major declines in large sharks along the U.S. coast have in turn triggered declines in shellfish and reduced water quality, proof that the ocean’s food web is collapsing, a groundbreaking new study reveals.

With the virtual elimination of large sharks along the U.S. east coast, such as black tip and tiger sharks, the species they used to eat — small sharks, rays and skates – have boomed in numbers. Cownose ray populations increased 20-fold since 1970 and as a direct consequence, shellfish like scallops that the cownose ray eats have been nearly wiped out despite major conservation efforts.

The cascade of impacts resulting from overfishing large sharks goes further still, marine scientist Ransom Myers and coauthors document in a paper published Thursday in Science. The loss of scallops has reduced water quality because scallops and other shellfish filtre sea water. And the cownose ray is now feeding voraciously on other shellfish, like oysters and clams.
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