“Coming at the issue from both the beginning with the rapid
spread of commercial whaling after WWII, and the end, with drastic declines
of kelp forests today, Springer, Estes and their six co-authors present
a domino theory of major ecosystem impacts and restructuring.
“It started with the capture of hundreds of thousands of great
whales from the North Pacific Ocean from 1946 to 1979. The paper's eight
authors argue that this removal of prey forced some killer whales to
seek alternative sources of food. Beginning with harbor seals (populations
collapsed early 70's - early 80's) then fur seals (mid 70's - mid 80's),
sea lions (late 70's - 90 's) and finally sea otters (90's - today),
the killer whales targeted populations of small, coastal marine mammals.
“The authors surmise that killer whales may have preferred harbor
seals and fur seals to sea lions because of the higher nutritional value
of harbor seals and because seals are less aggressive and easier to
“As the pinnipeds became comparatively rare, some killer whales
expanded their diet to include the calorically least profitable mammals
- the sea otters - with rippling ecosystem effects. By the late 1990's
low numbers of sea otters allowed an explosion of sea urchins and decimation
of the kelp forests due to the sea urchins' over grazing.
“ "The point of this story is not to vilify whaling and
exonerate overfishing," says Estes. "In principle we think
that when any species is exploited to excess - be it pollock, halibut
or whales - it may trigger a broad and devastating 'domino effect,'
and the ecosystem impacts are significant." ”