Interdependent marine ecosystem

An example from the seas (originally mentioned here years ago but removed because the link to the story no longer worked), was described by National Geographic Wild in a program called, A Life Among Whales (broadcast June 14, 2008).
It noted how a few decades ago, some fishermen campaigned for killing whales because they were threatening the fish supply and thus jobs.

A chain of events eventually came full circle and led to a loss of jobs:

• The massive reduction in the local whale population meant killer whales in the region (usually preying on younger whales) moved to other animals such as seals;
• As seal numbers declined, the killer whales targeted otters;
• As otter numbers were decimated, the urchins and other targets of otters flourished;
• These decimated the kelp forests where many fish larvae grew in relative protection;
• The exposed fish larvae were easy pickings for a variety of sea life;
• Fishermen’s livelihoods were destroyed.