Nature is a very complex, interwoven web of plant and animal species, ecological and environmental relationships, and an endless multitude of actions and reactions. To survive, it is constantly changing, adjusting to shifts in conditions - sometimes slowly and sometimes dramatically. Therefore, to predict the totality of change that occurs with the loss of a species is, to say the least, challenging. We like are answers neat and tidy. We are prone to look for silver bullet solutions, one size fits all remedies, and we have a tendency to view consequences in linear domino-like chains.
However, when you speak with ecological scientists, they think in terms of trophic cascade when considering man's impact on the environment. Changes are not simple and the ultimate outcome - particularly when nature is constantly trying to adjust for the sake of survival - becomes extremely hard to predict. It can be done but it requires complex modeling and varying degrees of confidence, and is often couched in the realization that other mitigating factors can alter the outcome of a particular situation for better or worse.
In the area of shark conservation, to stress the urgency of their cause sometimes passionate shark conservationists will predict outcomes involving the loss of sharks that don't necessarily take a variety of factors into account. They are fervently trying to make a point and will sometimes use an "A equals Z" approach that I find can be counter-productive because it strains credibility. One such equation is that without sharks the planet will lose most of its oxygen. To borrow a popular Hollywood expression about excess, they are "jumping the shark" in trying to make a simple statement about the ramifications on the environment if sharks were pushed to the edge of extinction. It's meant to alarm people but it pushes the envelope of rational, science-based discourse beyond the boundaries of common sense. And the result is you can lose the very person you are trying to convert.
Two blogging colleagues in the shark conservation field - Da Shark of the blog, The Best Shark Dive in the World, and Shark Diver of Underwater Thrills:Swimming With Sharks - take great exception to the shark vs. oxygen theory. Their writings can reveal, shall we say, a colorful and blunt temperament at times but they make some solid points in several recent posts on the subject. It makes for some good and entertaining blogosphere reading.
Certainly, sharks need to be conserved and protected as they play a critical role in maintaining the balance of a marine ecosystem. But they are not the only players in the game. At the very least, sharks are emblematic of what is happening to a variety of important species, from tuna to wolves to polar bears. And collectively, the totality of losses can produce negative impacts that can push some of nature's systems and capabilities to perilous tipping points, exceeding it's ability to adjust or recover.
But we must be careful as to just how far we wish to go in capturing the attention of a yet unengaged audience. If we lose our oxygen from the loss of sharks, then do we keep or even gain more oxygen by saving all sharks? Does that mean that the effects of fossil fuels will be negated or that ocean acidification becomes yesterday's news? How the marine ecology of, say, Fiji would be impacted by a severe decline in the island's reef shark population could be quite different from that of the Bahamas, or the loss of pelagic sharks in the Pacific could have different repercussions in the Atlantic. It becomes a very complicated image when we try to look at the big picture and so comprehensive conclusions must be measured and well thought out.
Shark conservation is necessary and important because it shines a light on our ignorance and indifference and identifies an important player in nature's cast of thousands. However, if we are to get people on board to the plight of sharks and other species or environmental threats - whether on land, in the sea, or in the air - our efforts must be based on the solid and, admittedly, often complex evidence that science can provide. It is a complicated world we live in and simplistic declarations of doom do not serve the cause, no matter how sincere the intentions.