An interesting article in today's New York Times discusses a newly-discovered connection between the lack of sardines and global warming. It appears that these tiny fish eat, or used to eat, massive amounts of phytoplankton, which are tiny plants floating in ocean currents. With the sardines exploited and overfished, the phytoplankton proliferates, dies, and rots. As it rots it produces methane, a powerful greenhouse gas.
The study was conducted in Africa, but could be relevant to the collapsed sardine fishery off the northern California coast. Just one more lesson of the dangers in massively altering systems we don't yet understand.