This ties in with an article I was reading in Mother Jones about the pending extinction of half the worl'd species in the next century. One of the concepts in the article is that of "co-extinction" in which one species goes extinct, and others who depend on that species are also effected, and often go extinct themselves. The flip side of this is when a foreign species (with few or no natural enemies, or enemies that have been diminished by some outside force as the fishing of the tuna, sharks, and swordfish has) comes in to a new territory and upsets the balance as the squid are doing in the article above. Of course, the human species has been doing that for years, which is why we are in such a state, now.