Simulating everything

Compared with climate, modelling of ecosystems is at an early stage

But it will help sustain biodiversity when more mature

EVERY FEW weeks from June 1963 until July 1968, Robert Paine, a zoologist, made the journey from Seattle, where he taught at the University of Washington, across Puget Sound to the rocky shores of Mukkaw bay. There, he had found virtually pristine tide pools that teemed with life—limpets, anemones, mussels, seaweeds and purple-and-orange seastars known as Pisaster ochraceus. The unspoiled landscape offered the perfect setting for what was to become a seminal experiment in ecology. On each visit, Dr Paine systematically removed all the seastars he could find from one patch of rock, lobbing them as far as he could into the waves.

He did this for five years, all the while carefully documenting how the shoreline communities evolved. Very little changed in the untouched areas. But in his seastar-free zone, everything was altered. Pisaster is a greedy carnivore that feasts on mussels, barnacles, limpets and snails. Released from their predator, these species began to spread out. The acorn barnacles took over first. Later, they were displaced by goose barnacles and mussels. By removing just one species, Dr Paine had triggered a domino effect. Soon, the number of species in the community had dropped from 15 to eight. By 1968, the mussels had taken over completely.

Dr Paine dubbed Pisaster a “keystone species”; remove it and the ecosystem is transformed. Large herbivores like rhinos are keystone species, spreading seeds of the plants they…