Without Predators...

Over the weekend I read the most important book I've come across all year, Where the Wild Things Were: Life, Death, and Ecological Wreckage in a Land of Vanishing Predators, by William Stolzenburg. I've read hundreds of environmental books over the years and certainly had a degree of awareness about how critical predators are for ecosystem health, but this book shot home that truth in a most brutal way.

Without predators it all collapses. Without predators we enter a cascading spiral of extinctions, an extreme loss of biodiversity, a dumbing down of life. It's clear we've doomed ourselves in so many other ways already, but this is one of the biggest nails in the coffin. Where does the spiral end, if not in the extinction of virtually all higher lifeforms? Sure, things will survive, but we're not likely to be among the living, and the world left behind will be a very sorry place for a very long time.

The book documented many examples of these cascading spirals of loss, what are called "trophic cascades", brought about by the loss of top predators.

For instance, when we eradicated the deer's predators we created a cascade leading to the loss of countless other species in those habitats: songbirds, bears, orchids, trillium lilies, pollinating insects, cedars, whole forests, etc. In some places that have been studied, up to 80% of species have been lost due to the overpopulation of deer. I'm oversimplifying a bit--the deer cause the brunt of the damage, but certainly not all of it. Surging populations of raccoons, skunks, and weasels, for instance, are probably more direct culprits for the loss of songbirds (at least the ground-nesting and understory-nesting birds) than deer, although the deer are responsible for clearing out the understory.

The most interesting thing I learned from this book is that fear creates diversity. The author described what happened when wolves were reintroduced to Yellowstone. In the seventy years the park had been wolfless, the burgeoning elk population had decimated the park ecosystem. Even the rivers were in horrible shape because no vegetation was able to grow to hold the banks in place. Once wolves were reintroduced, scientists noticed thickets of willows beginning to spring up, mostly in the river bottoms. This was unexpected because there were still far too few wolves to have any serious impact on elk numbers. The elk should still have been browsing down any new willow shoots that sprang up.

What the researchers eventually realized was that the willows were coming back because of fear. When the elk had no enemies, they browsed indiscriminately, everywhere. But once they had an enemy again, their old survival instincts reawakened. They recognized certain types of terrain to be dangerous and thus began avoiding them. Mostly these places were river bottoms, stream courses, and other incongruities in the land that would cause them to slow down during a chase. A wolf, who is so much lighter and more agile than an elk, doesn't need to slow down nearly as much to accommodate changing terrain and can catch up with an elk more readily in such places. So when the fear returned, the willows also returned--in river bottoms and other places that posed a hazard to the elk. Once the river bottoms repopulate with willows, it's expected to have a (positively) cascading effect--halting erosion, bringing back songbirds and beavers, fish and amphibians, aquatic insects, etc.

In another part of the book a French ecologist, Jean-Louis Martin, studying an archipelago in which some of the islands were free of deer and others overrun by them, said, "For me it was sort of a major lightbulb which came on. [...] Suddenly what I realized working there [is] that carnivores are mainly not animals which eat prey, but which change the behavior of prey."

It's this changed behavior, caused by fear, which holds the world together. And we've largely wiped out the predators, thus changing the behavior of vast numbers of species. We need to occupy niches constrained by fear. Fear is what creates diversity. An elk-free thicket of willows is a pocket-sized niche--a diminutive ecosystem which evolves its own flora and fauna. Humans on the savannas of Africa knew to avoid thickets, which might be hiding lions, so those were human-free thickets. What evolved in those thickets was surely different than what evolved in the surrounding open land where humans modified the environment with their hunting and gathering activities and their mere presence.

When you think about this fear-effect, and multiply it by all the many species and all their different fears, you have millions or billions of niches and microniches (probably an infinite number of niches)--the very richness needed for innovation and speciation.

But eradicate fear and you erase diversity. It all falls apart.

Simply by virtue of being born a living being on this planet, we enter a compact that requires us to participate in the intricate dance of eating and being eaten, and that means dancing with fear. All of the diversity here comes from this dance of life and death. Life is the process of energy being transformed by death. As we feast on death and try to avoid being feasted on for as long as possible we create an environment primed for diversity.

Humans are the only animals with the power, on a large scale, to eradicate fear. You can look at at least the last ten thousand years of our history and see it as nothing more than an all out war against fear. And we've done a damn good job of eradicating fear, haven't we? We don't worry about being ambushed by a lion when we hang out the wash, or warily watch the skies so that a black eagle might not carry off one of our toddlers, or pay any attention to our surroundings when we're on our ski vacations to make sure we don't find ourselves surrounded by a pack of wolves. It's a nice world isn't it?

But by denying fear, by trying to make life pretty and serene and safe at all times, we are in fact denying life.