This starfish wasting syndrome is not funny folks. In case you haven’t heard the story, an epidemic of disease among Pacific starfish, specifically pisaster ochraceous, or Ocher Starfish, the big orange “stars” of beaches and tidepools, is causing them to waste away, fall apart and die in alarming numbers.
Humans have adored these strangely beautiful creatures for eons, and their popularity hasn’t waned one bit, but within the tidal ecosystem, the ocher starfish is a feared predator, at least to the degree that a bivalve mollusk can experience fear.
Frightening or not, the ocher starfish plays the same role in the intertidal zone as lions do on the Serengeti, or that wolves do in Yellowstone National Park. The ocher starfish is the apex predator of Pacific tide-pools. In fact, scientists have learned a lot of what they know about apex predators, like lions and wolves, from studying ocher starfish.
Ecology, especially ecosystem ecology, is a very new field of scientific inquiry. It seems hard to believe today, but before World War II, nobody really gave a rats ass about how ecosystems worked. The story of civilization has been one of “plunder first, ask questions later,” and so it goes that the science of studying ecosystems didn’t get under way until well after most of the world’s ecosystems had been severely impacted by industrial exploitation. As a result, we may never know how a healthy ecosystem operates. In a sense, studying ecosystem ecology today, must be a lot like trying to learn about antebellum life and culture by observing a confederate field hospital towards the end of the Civil War.
Still the nascent field of ecosystem ecology can teach us a few things about what happens to an ecosystem when you remove a keystone species. In fact, one of the landmark studies in the field of ecosystem ecology looked at the effects of removing just this particular species, pisaster ochraceous from a tide-pool ecosystem.
The scientist in this study, Robert T. Paine, marked off two equal sized patches of tide-pool habitat. A couple of times a month, Robert would go to one of those marked off areas, and within it he would meticulously remove every single ocher starfish from that area, and hurl them, as far as he could, into the surf. In the other marked-off area, he did nothing but observe.
Every two weeks or so, for a year, Robert went down to his little marked-off areas and began chucking starfish. Doesn’t this make “ecosystem ecologist” sound like a pretty sweet job? Spend your days splashing around on the beach skipping starfish across the water. How do I sign up? I guess his hands got pretty torn-up from the abrasive skin of starfish, but it still sounds like a pretty good job to me.
Over the course of the year, Paine observed the results of his strange new obsession. In the area where Paine had removed all of the ocher starfish, the ecosystem collapsed. Initially Paine observed dozens of different species living together in that area. Within a year, half of those species had disappeared completely, and those that remained, did so only tenuously. Before long, all but one species completely vanished from the experimental area.
The only species left inhabiting the area, had completely taken over. Every square inch of the marked off area was covered with large mussels, mytilus californianus, the ocher starfish’s favorite prey. In absence of starfish, nothing could stop the mussels from squeezing everyone else out of the picture, leaving a desolate monoculture where there was once a thriving, diverse ecosystem.
Paine published the results of his experiment in 1966 in the scientific journal American Naturalist, and it has become a foundational work in this emerging new field. Paine’s experiment revealed that certain species, specifically predators, have a greater effect on their ecosystem than their numbers suggest.
Paine’s work with starfish eventually led to federal protection of keystone predators like the spotted owl, and to the reintroduction of wolves into Yellowstone National Park. Paine had demonstrated that predators are critical to maintaining healthy ecosystems, and that without them, complex and diverse ecosystems quickly collapse into desolate wastelands overrun with pests.
Like I said, ecosystem ecology is a new field, and its progress has been greatly compromised by the impacts of industrial exploitation. As a science, ecosystem ecology remains in its infancy, especially regarding marine ecosystems, but when it comes to the question “What happens to intertidal ecosystems when ocher starfish disappear?” thanks to Robert T Paine, science can give us a pretty good answer. Unfortunately the answer itself is neither pretty nor good.