The short film “Some Animals Are More Equal than Others: Trophic Cascades and Keystone Species” opens by asking two fundamental questions in ecology: “What determines how many species live in a given place? Or how large can each population grow?” The film then describes the pioneering experiments by Robert Paine and James Estes, in the 1960s and 1970s, which started to address them. Paine’s experiments on the coast of Washington state showed that the starfish is a keystone species, having a disproportionately large impact on its ecosystem relative to its abundance. Estes and colleague John Palmisano discovered that the kelp forests of the North Pacific are indirectly regulated by sea otters, which feed on sea urchins that consume kelp. The presence or absence of sea otters causes a cascade of direct and indirect effects down the food chain, which in turn affect the structure of the ecosystem. These early experiments inspired countless others on keystone species and trophic cascades in ecosystems throughout the world. Source http://www.biointeractive.org film guide and educational materials.
Paine dealt a serious blow to the dominant view in ecology of the time: that ecosystems are stable dramas if they have a diverse cast of species. Instead, he showed that individual species such as Pisaster are prima donnas, whose absence can warp the entire production into something blander and unrecognizable. He described these crucial creatures, whose influence far exceeds their abundance, as keystone species, after the central stone that prevents an arch from crumbling. Their loss can initiate what Paine would later call trophic cascades — the rise and fall of connected species throughout the food web. The terms stuck, and ‘keystone’ would go on to be applied to species from sea otters to wolves, grey whales and spotted bass. —Ed Young, Nature Magazine January 16, 2013 Scientific American
Robert T. Paine, (Robert Treat Paine III), American ecologist (born April 13, 1933, Cambridge, Mass.—died June 13, 2016, Seattle, Wash.), was an icon in the field of ecology and the originator of the keystone species hypothesis, which posited that some species (typically large predators) have a disproportionately large effect on the biological communities in which they occur. Paine received a B.S. (1954) from Harvard University and earned a Ph.D. in zoology (1961) from the University of Michigan before joining (1962) the University of Washington as an assistant professor in the department of zoology. Paine unveiled (1969) his keystone species hypothesis after researching the ochre sea star (Pisaster ochraceus), a predatory species in the tidal pool communities on Tatoosh Island in the Pacific Northwest. After removing all of the sea stars from the tidal pool, he discovered that the mussel population rose dramatically. The mussels covered the rocky surfaces of the tidal pool to the detriment of other tidal pool denizens (limpets, barnacles, and sponges) and thus changed the structure of the tidal ecosystem. He noticed similar patterns in kelp forest ecosystems when sea otter populations declined; the population of their prey, sea urchins, grew large, consuming enough kelp to drive away other animals that would normally feed on that seaweed. Paine’s groundbreaking keystone species concept, which was later clarified to describe the impact of strong single-species relationships that were out of proportion with the species’ biomass in the ecosystem, became an important factor in conservation; many ecologists used his model to guide their decisions on which habitats and ecosystems to protect to maximize biodiversity. Paine was presented with the MacArthur Award from the Ecological Society of America in 1983 and the International Cosmos Prize in 2013. Encyclopdia Britannica
