by Michaela Barnett

In 1963, Bob Paine started plucking sea stars off the coast of Washington and hurling them out into the Pacific deep. Bob wanted to see what, if anything, would happen when ochre sea stars were no longer present in the vast cast of characters in the rocky intertidal zone. At the time, ecologists believed that ecosystems would remain stable if they maintained a diverse variety of species—that no individual species could affect an ecosystem more than any other. The lanky scientist hurling sea stars into the Pacific deep changed that paradigm and coined a term that bounces around in academic papers to this day: keystone species. Today, some fifty years later, species ranging from wolves to grey whales are now known as the “keys” to their ecosystems.

Despite the fact that Bob only removed one species out of many in the intertidal pools, once those sea stars were gone, the zone slowly slipped from a functioning and stable ecosystem to one of dull homogeny. What had been a diverse, thriving community full of algae, anemones, barnacles, limpets, mussels, and ochre sea stars became the ecosystem equivalent of a stricken city taken over by the mob. Black mussels moved in and dominated the zone within a year. Other species fled. Ochre sea stars had been responsible for maintaining a dynamic, complex balance. When they were popped off the rocks with a crow bar and tossed into the waves, the whole system crumbled. It tipped from a stable state to one that was anything but, a microcosm reflecting a heating planet and the state of my mind. 

Remove just a few activities from the daily rhythm of life and a black cloud of depression moves in, crumbling the whole system. At a time when most of our ecosystems are disintegrating from habitat destruction and climate change, a parallel process seems to be occurring in the human psyche. Depression is now the leading cause of ill health and disability worldwide, rates increasing at all ages. The world is out of whack. The planet is feverish and its people are ill. 

I do not know whether ecological health and mental health are intertwined. But for whatever reason, my descent into depression mirrors the cascade that occurs in an ecosystem when a keystone species disappears.

I first made the connection on a phone call with my therapist, Mary. I was lamenting to her how I felt like I had to do too many things to maintain even a base level of functioning. “If I just go one or two days, god forbid three, without doing the things I know I need to do, everything crumbles.” 

Mary is a good therapist. She gives me time to work out my problems. 

“I just want to be stronger. More resilient. I want to know that I can just live and exist and not have to check every box every day in order to not fall into a depressive state,” I told her. 

Mary asked me to identify the things I have to do, and I listed them off: exercise, writing, meditation, and time spent outside. 

“And you feel like you shouldn’t have to do these things in order to function?” 

“Exactly. I should be more resilient,” I said. It had been a hard week: too many black mussels, not enough sea stars. And I was becoming that out of whack ecosystem. My lack of resilience was tipping me into a different state. Like a failing ecosystem, I was no longer able to cope with disturbances. The black mussels were moving in.

I wanted to be resilient, but I wasn’t thinking about how my own mental ecosystem functioned.  Unwittingly, I had been hacking off starfish and tossing them away, leaving gaps that allowed my mind to be invaded by dark, fecund mussels. Reintroducing starfish seemed increasingly vital, yet more daunting as the mussels multiplied upon themselves. 

Bob Paine moved his experiments to Tatoosh Island in 1967 and saw the same cycle repeat itself on a larger scale. He experimented by systematically removing other species from the ecosystem to see if it had the same effect, but most of their absences did not change the ecosystem dramatically.  Only two other species out of many had any comparable effect: a sea urchin and a mollusk known as a chiton. The presence of these three species had a huge impact on the resiliency of the system; others, not so much. 

Disturbances seem more common these days; resiliency harder to come by. Keystone species have been hard hit by changing weather and warming seas. The increased incidence of sea star wasting syndrome (SSWS), first recognized in ochre sea stars, has decimated populations of sea stars along the Pacific coast from Alaska to Mexico. The warming of coastal waters speeds up the progression of the disease, especially in adult sea stars. As the sea stars wither and vanish from the rocks, the mussels are taking over yet again. And when there are too many, there is no room for anything else.

The same is true in my own ecosystem. Exercise, writing, time outdoors: these function as sea stars, urchins, and chitons – eating algae and shaping my environment. Gardening, cooking, working – secondary species – add biodiversity and color. And of course, the black mussels capture the hegemonic apathy of depression. Any disturbance to keystone species and activities can tip an ecosystem over the edge. Sometimes I feel like my brain is being tinkered with by someone else and affected by changes I cannot control. Sometimes I feel like Bob Paine, experimenting and recording the results. Sometimes I feel like the sea star itself, watching the mussels move in.