nov 17th, 2006
prof palumbi gave a great talk as part of the stanford summer science series, on the recovery of monterey bay (the one with the famous aquarium) after it had been devastated by canneries and overfishing (see by the way john steinbeck's cannery row and log from the sea of cortez, the latter especially is a non-fiction classic on marine biology).
what prof palumbi basically said -- i paraphrase from memory -- was that the disruption of the food chain was what caused the collapse of the ecosystem in the bay. that is, sea otters were captured and killed in large numbers for their pelts. sea otters are the natural predators of abalone and other such crustaceans. the crustaceans feed on the main biomass, the giant seaweed of the bay (rough analogue of the rain forest's tree biomass).
once otters were decimated, abalone populations exploded, and they ate up a lot of the seaweed. this caused the entire food chain to be disrupted. the population of sardines etc. collapsed (of course also from overfishing). the area became the equivalent of a marine desert.
then what happened is that people simply left the ecosystem alone, and wonder of wonders, it has now come back!
the answer seems to be to protect the entire ecosystem, not just individual species.
this has relevance to india's vanishing tiger and elephant biospheres, as well as the western ghats ecosystems that have been decimated with plantations.
it may not be too late yet, but it's rapidly getting there.