Where the Wild Things Were: Life, Death and Ecological Wreckage of Vanishing Predators

  • William Stolzenburg
Bloomsbury: 2008. 240 pp. $24.99. 9781596912991 | ISBN: 978-1-5969-1299-1

Walking in the dark across the forest clearing to my hut after dinner, I hear a tiger roar. The sound resonates through the trees making the animal sound frighteningly large, like some science-fiction monster. A herd of gaur — sleek, muscular and menacing wild cattle — then emerge from the shadows. “They, and not you, are tiger food,” tiger expert Ullas Karanth tells me, but the hairs on the back of my neck defy his reassurance. Being where predators can eat you is a rare experience, and getting rarer. What happens when they vanish from ecosystems is the subject of this entertaining book, Where the Wild Things Were.

Star turn: removing predatory starfish from shores allows different species to take hold. Credit: S. MAFFORD/GETTY IMAGES

Journalist William Stolzenburg describes how the removal of top predators affects species at lower levels in the food chain. He does so through the experiences of the researchers who discovered these relationships. He portrays prominent ecologists such as Robert Paine and Charles Elton in their graduate-student days, when their results were new and controversial.

Where the Wild Things Were starts with Paine's 1966 influential paper on removing the starfish Pisaster ochraceus from rocky shores. His experiment was simple and effective, and has been imitated many hundreds of times. Paine showed that without the top predator, intertidal communities soon hold very different sets of species. Without predators, predator-sensitive species can take over communities in which they would otherwise barely survive.

On a vastly greater scale, scientists generally accept that humans exterminated many large animals shortly after their first contact with them. In the 1960s, geoscientist Paul Martin lectured on how the dung of giant sloths — “sloth shit” as he called it with relish — stopped accumulating across widely scattered caves in North and South America at much the same time, some 11,000 years ago. Martin's result defied the conventional wisdom at the time, that noble savages could not have killed off the sloths so quickly and over such a large area. This story was a pure historical reconstruction, for human impacts cannot be tested experimentally. However, the progression of human contact, first in Australia and later on smaller oceanic islands, provides some replication of this process.

At a scale between the neat experiments of Paine and Martin, Michael Soulé studied the absence of predators in Californian canyons accidentally isolated by the rapid growth of tract housing in San Diego. The longer the isolation period and the smaller the canyon, the less likely were the few remaining large-bodied predators to survive. In their absence, smaller predators ran amok and eliminated ground-nesting birds. Ecologist John Terborgh investigated islands isolated by the flooding of Lake Guri in Venezuela. Similarly, a lack of predators on these islands precipitated an intricate set of cascading changes, involving plants, insects and vertebrates. Jim Estes, a marine ecologist, carefully pieced together the interactions of killer whales, sea otters, urchins and kelp by combining historical and geographical sources. Again, the message is complexity — urchins eat kelp, sea otters reduce urchin numbers and are thus good for kelp — and so on, up a long food chain involving these and other species.

Stolzenburg's emphasis on history is also a weakness of the book, which stops short of present theory and practice. In 1960, Nelson Hairston, Fred Smith and Larry Slobodkin proposed that the world is green because predators keep herbivores under control and allow plants to flourish. Two decades later, Lauri Oksanen and his colleagues posited that a green world makes little sense if you are standing in tundras, deserts or grasslands. Where plant production is very low, the few transient herbivores eat little overall so their removal would not be noticed. In slightly more productive systems, more abundant plants support effective herbivores that can strip the greenery but are not themselves eaten by larger predators in significant numbers. Only in the most productive ecosystems would predators control herbivores and greenness prevail.

Whatever the merits of these arguments, the ubiquity of top-down predation is still being debated. Stolzenburg acknowledges this in his epilogue, but quickly concludes that predators are in control, pounding home the point with examples in every chapter. Decades of experiments show that nature is more nuanced.

Stolzenburg is forthright about the consequences. “Ecological wreckage in a land of vanishing predators” is part of the subtitle, and the back cover page notes “chaos in their absence, brazen mobs of deer, marauding racoons, urchin-scoured reefs, [and] bizarre impoverished landscapes of pest and plague” as examples.

The loss of predators is a bad thing, but the outcomes of experiments, following Paine's intertidal work, are more complex than this simple Armageddon. Remove a predator and the odds are nearly equal that a given prey species will flourish or flounder. A prey species can easily decrease if the predator controls another prey species that, when unchecked, can outcompete its opposition. As Bruce Menge showed in 1995 in his insufficiently appreciated synthesis, this is but one common pattern in many possibilities. Moreover, communities with more species display richer patterns.

What might we do about the loss of predators? In Where the Wild Things Were, Stolzenburg discusses only “re-wilding”— a fanciful attempt to return North American ecosystems to how they were before humans intervened. Natural ecological processes could be revived in US prairies, for instance, by replacing long-extinct mammoths, sabre-tooth cats and rhinos with their twenty-first-century ecological equivalents from Africa. One should not deny a man his fantasies, but the reality of restoring large species provides more immediate, yet still important challenges, including how much land is needed for various species.

The American Prairie Foundation is restocking prairies with pure-bred bison and smaller species, such as prairie dogs and their highly endangered predators, the black-footed ferret. The Wildlands Project is a US effort to connect existing wild areas from Alaska to Mexico to make them large enough to support large viable populations of predators. Its South African equivalent, the Peace Parks Foundation, notes that even the national parks of Africa are not always large enough to support lion and wild dog populations, and wants to connect them into 'mega parks'.

Another South African experience is not widely appreciated. During that nation's decades of political and academic isolation, game biologists conducted hundreds of mostly successful reintroductions of many herbivore species, including rare black rhino, black wildebeest and bontebok antelope, to their historical range in dozens of provincial parks. Numerous private game reserves have now extended those experiments, raising practical but difficult questions about how large reserves must be to hold predators or even their prey.

A few years ago, I sat munching on my lunchtime sandwich, watching wildlife that ought only appear together in a dream. Fifty wild horses stared at me. The red deer grazing behind them were oblivious. Farther away a large flock of barnacle geese had stopped to breed, and overhead soared a breeding pair of sea eagles. Wild horses have long disappeared from Europe; in the twentieth century, barnacle geese bred only in the high Arctic, and deer and eagles were found only at the sparsely populated fringes of the continent. Some 5 metres below sea level, the Oostvaarderplassen nature reserve in the Netherlands is an unlikely place to have restored something close to Europe's post-Pleistocene fauna. That these big, wild things now live there shows that nearly anything is possible. Surely, the exciting story is where the wild things were, and will be once again.