James A. Estes: An ecologist’s quest to understand nature

For five decades, Jim A. Estes studied sea otters in the Aleutian archipelago of Alaska, discovering how otters structured entire communities. By consuming sea urchins, otters released kelp from herbivory, kelp beds flourished, and kelps sheltered a diversity of fishes, and invertebrates. When otters were extirpated by paleohumans, modern humans, or killer whales, urchins proliferated, reduced kelp forests to “urchin barrens,” and species-rich assemblages of fishes and invertebrates were lost. These losses affected seals, eagles, sea gulls, fishes, and sea stars that depended on these prey as well as adjacent habitats that had been nourished by exported kelp production. Jim’s research became the poster child for keystone species, trophic cascades, and the critical role of predators in structuring ecosystems. Similar discoveries followed in freshwaters, forests, and grasslands.