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Loss of top predators a disturbing trend
By David Suzuki

11th February 2003

I am reviewing the manuscript of a book titled Monster of God by the wonderful natural history writer, David Quammen. He documents our relationship with the small group of animals that actively seek and eat human beings, animals in sexist days referred to as "man-eaters."

Quammen begins: "Great and terrible flesh-eating beasts have always shared landscape with humans. They were part of the ecological matrix within which Homo sapiens evolved. They were within the psychological context in which our sense of identity as a species arose. They were part of the spiritual systems that humans invented for coping."

Who are these species that dare to stalk us as edible prey? After discounting hyenas, jackals, wolves, wild dogs, and piranhas, the list is surprisingly short: big cats, a couple of giant snakes, the Komodo dragon, some bears, and a few sharks.

Quammen contends these animals remind us we are not indisputably at the apex of evolution; to some species we are edible meat. These creatures have been terrifying monsters to some, gods to others, critical parts of our spiritual and psychological development.

But today, thanks to the incredible power of human imagination, curiosity, and inventiveness, we have amplified our survival capabilities far beyond any other species to a point where we now threaten our own existence.

Sharks have long been demonized (remember the movie Jaws?), but natural history documentaries are revealing their fascinating lives, and scientists are realizing the vital role that predators at the top of food chains play in terrestrial and ocean ecosystems. Nevertheless, sharks remain vulnerable as targets of hunters protecting swimming areas, accidental catches in nets, and deliberate prey for food.

The consequences are revealed in a shocking paper published by Canadians in a recent issue of Nature. Of eight shark species for which there are catch records, three (including the great white) have declined by more than 75 percent in only 15 years! Four more have declined by more than 50 percent, while one has dropped by "only" 40 percent. They now are the marine equivalent of canaries in the coalmine.

What we've learned in the past century is that human activity is now powerfully disrupting the fabric of the natural world. Pesticides, hormone disrupters, CFCs, greenhouse gases, artificial fertilizers, trawlers, clearcut logging, urban sprawl, megadams, and many more technologies and activities are exceeding nature's regenerative capacity and upsetting the balance that provides many "services" on which we depend.

The very simple but profound truth is that despite our sophistication, we remain biological beings as dependent on clean air, water, soil and energy as any other creature. Those basic needs are delivered to us by the complex interaction of the web of living things with the physical and chemical processes of the planet. By disrupting that web -- for example, by introducing more greenhouse gas into the atmosphere than can be reabsorbed -- we set off a ripple of effects through the web with consequences we cannot anticipate.

The probability that the rapid changes being induced by our species will improve our lives is infinitesimally small because the balance that existed was shaped by millions of years of evolution. Let me illustrate this point with a precision Swiss watch developed over decades. If we took the back off the watch and jammed a probe into the gears, there is a very small chance the watch would work better, but the overwhelming likelihood is that it will be impaired.

That's the way it is in nature. The catastrophic decline of a group of major marine predators like sharks is a warning that something is seriously out of balance. And ultimately, we are as tied up in the fate of the big predators as the animals themselves.

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Source: David Suzuki Foundation