James A. Estes / University of California Press / 256 pages
Serendipity tells the story of ecologist James A. Estes’ work researching the unexpected collapse of sea otter populations in the Aleutians—specifically, how these declines played into a larger collapse of other coastal-living marine mammals in the same region. Although this remains a controversial hypothesis, Estes ultimately concludes that post-World War II industrial whaling was the likely culprit behind the collapse: By eliminating the smaller whales that orcas once hunted, industrial whaling forced a dietary shift for the orcas toward seals, sea lions, and sea otters, thus driving down these populations.
The book uses these findings to ask the bigger question of how this might be applicable to other species of apex predators and their ecosystems around the world. Although the writing is somewhat technical, the book does an excellent job of explaining trophic cascades—whereby predators limit the density and/or behavior of their prey and in turn enhance the survival of the latter species’ prey—and how important apex predators are in shaping ecosystems. For example, after sea otters were hunted to near extinction for the fur trade, islands in the area suffered a collapse of their kelp forests. Why? Otters consume sea urchins. Sea urchins graze kelp. Without otters, sea urchins proliferate, in turn wiping out the kelp.
Estes ultimately supports the finding that ecosystems are strongly influenced by top predators and that their loss correlates with the loss of biodiversity on a global level.