If I'm reading you correctly, wagsy, you are suggesting that all population booms and busts, and any out-of-whack ecosystems in general, are the fault of humanity's meddling, past and/or present. That's a handy way of envisioning ecology––it's all our fault, one way or another, because we stuck our noses where mother nature didn't want us to––but it's not realistic or helpful. No doubt we've affected things in ways that otherwise wouldn't have occurred,and we can certainly quantify some of those effects, and we may indeed be triggering the sixth mass extinction in Earth's history. But now what? Do we simply scale back our ecological footprints across the board and hope for the best? After decades (or in some cases centuries) of commercial fishing, will we really save the declining populations by taking the simplest or most pleasingly intuitive approach? Once you accept that we're all in the game, and that there's no turning back to an Eden-like world (which never existed in the first place), the question and the challenge becomes, "Can we figure out ecosystem dynamics so that we can "meddle" (live our lives and not migrate to Mars) in a way that doesn't destroy the habitats and populations that we both depend upon and want to protect?" One way to answer that question and meet that noble challenge is to recognize that we can do damage even when we're trying to do right.
Which is why I bring up the MMA and the explosion of gray seals on Cape Cod. Of COURSE the decline of large pinniped-eating sharks (whites; maybe mature makos, too) may be our fault, and that may in turn have allowed the seals to thrive beyond where they were in the old days––or beyond where we or other species would like them to be. Maybe, maybe not. We really don't know, nor can we (though we can certainly compile compelling evidence and publish results in scientific journals). But anyhow, NOW WHAT? By limiting our proactive meddling to protection and moratoriums and the like, we are simply ignoring the possibility that we can screw things up just as severely by doing what seems right. So, now that we've got California sea lions living on the docks in SF, and grey seals setting up enormous colonies on the Cape, do we just assume "Well, this is probably the way it's supposed to be, the way nature intended it"? Are negative outcomes of conservation our fault in the same way that overfishing, habitat destruction, etc. are our fault? When we know that populations go boom and bust without our intervention, how do we identify when we are at fault? And what then?
In the case of the Alaskan otters, do we try to right things by protecting the seals and sea lions that the killer whales "should be" eating, with the hope that the otters will then come back and eat those overabundant urchins and put things back in "balance" (which never really existed)? Do we start harvesting urchins? Do we stop protecting the killer whales, since they're eating the otters? Do we just remove ourselves from the "equation" entirely, go vegan, and see how things look in a decade? Is one solution really any better than another? What are our criteria?
This stuff is tough. In fact, it's a lot tougher than rocket science. We've affected some systems so completely, from top to bottom, that it's really f-ing hard to know what the hell is going on. Here's a weird modern picture: a trawler on Georges Bank hauls up a bag full of groundfish, and tunas and seabirds follow the net up so they can feed on herring and other stuff that slips through the codend. Pilot whales follow the boat all week, living off bycatch and even tripping open the net to get at the catch. Gulls, cormorants, and other birds literally eat nothing but the discarded offal from the boat. The bottom is scarred and churned up by the heavy gear, ruining habitat for some while improving it for others. From surface to benthos, it's all affected. So, what would happen if the trawlers went away? Beats me, but I'd prefer if we try to figure that out and weigh our options instead of simply assuming that the system would heal itself quickest or most completely if we simply scuttled every trawler and went to sea only to take nice photos.
shawnh,
Last I heard, the IUCN suggests that 20% of elasmobranch species are endangered. My point is not that that figure is "only" 20% and therefore insignificant, or that we should only worry about what's on the Red List, but that we ought to acknowledge that some sharks are okay and others aren't. This is not because I want to paint a rosy picture or put rose-tinted glasses on you, but simply because those are the facts as best as we can tell. It's kind of strange that we talk about sharks as though they are this single entity––I can't count the number of times that sharks are still referred to as "a species" in popular media––whereas we are fully capable of getting specific about endangered birds or endangered terrestrial mammals. For example, everyone knew of the bald eagle's plight when they were endangered but nobody lumped them in with herring gulls or blue jays. Likewise for polar bears versus white-tailed deer. Let's get specific, let's get detailed, and let's admit that the path that we take toward a healthier planet is never going to lead back to Eden or result in a "balance of nature."
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