The starfish story, revisited

Walking along a beach, I encountered a girl picking up starfish stranded on the beach.  She was throwing them, one by one, back into the ocean.

"There is a time and place for individual acts of kindness," I told her, "but this isn't it.  There are thousands of starfish on this beach alone.  Are you going to come back every day?  What about all the other beaches?  What difference can you possibly make?"

She replied, "It will make a difference to the hundreds of mussels each of these starfish will eat in its lifetime."

"So," I interrupted, "each starfish is just a Pisaster waiting to happen?"

"You could think of it that way," she continued, "but according to this recent article in Science1, 'Paine's classic experiments in Washington state demonstrated that without predation on mussels by Pisaster, a diverse assemblage of low intertidal algae and invertebrates shifted to a monoculture of the competitively dominant mussel M. californianus'."

"Isn't the role of biodiversity in ecosystem function still controversial?2" I asked.

"Yes," she agreed, "but I like biodiversity."

"So do I," I said.

1) E. Sanford (1999) "Regulation of keystone predation by small changes in ocean temperature" Science 283:2095.
2) Huston et al. (2000) "No consistent effect of plant diversity on productivity" Science 289:1255a;
Grime (1997) "Biodiversity and ecosystem function: the debate deepens" Science 277:1260;
Goodman (1975) "The theory of diversity-stability relationships in ecology" Quarterly Review of Biology 50:237