Passenger Pigeons: Why Extinction Matters

Passenger Pigeons by John James Audubon

Passenger Pigeons by John James Audubon

I had a dream last night that I was keeping dodo birds the way one might keep chickens. They had been resurrected, phoenix-style, through DNA lab work. I was excited to tell my stepmom – this would be a great bird to add to her life list.

In the category of birds that have run afoul of man’s voraciousness, perhaps only the passenger pigeon occupies a place in the public’s consciousness equal to its relative the dodo. It’s been 100 years since the last passenger pigeon died.

In college I wrote about the ecological implications of the extinction of the passenger pigeon (the paper was creatively titled Ecological Implications of the Extinction of the Passenger Pigeon). During the course of the 19th century, the passenger pigeon population plummeted from about 3 billion birds to virtually none, killed for food, for animal feed, for sport, and to protect crops. This was exacerbated by loss of habitat as forests were cleared. I focused on three areas where the loss of passenger pigeons likely affected the ecosystem.

1. Passenger pigeons ate a variety of nuts, fruits, insects, worms, and grains. During certain seasons, beechnuts made up a large part of the passenger pigeon diet. Imagine a billion or so passenger pigeons descending on a beech forest to gorge themselves on beechnuts and other food. The pigeons helped maintain healthy forests by dispersing nuts, keeping potentially harmful insect outbreaks in check, fertilizing the forest floor, and even occasionally destroying individual trees, which would clear the way for younger trees. Might the presence of passenger pigeons have been enough to minimize the effects of beech bark disease, caused by scale insects imported from Europe in the late 1800s?

2. Passenger pigeons ate a lot of food, but they also were food. In addition to providing a tasty meal for numerous mammalian predators, many raptors would have feasted on the cornucopia of pigeons. In particular, peregrine falcons, famously affected by DDT, may have been more susceptible given that an important food source was no longer available.

3. And passenger pigeons didn’t just provide food for larger animals. The American burying beetle uses small bird and mammal carcasses to rear its young. The historical range of the burying beetle was similar to that of passenger pigeons. Today this beetle is found in only a few small areas, and is critically endangered.

Of course there are innumerable ecological functions that changed with the loss of passenger pigeons, given that there had been around 3 billion passenger pigeons prior to their eradication.* We often look at the ecological implications of human interference with nature, but this is generally presented based on how it affects humans, whether environmentally or economically.

Do we really care about the American burying beetle, beech trees, peregrine falcons, or passenger pigeons aside from the services they may provide for us? By discussing the “ecosystem services” that species provide for humans, well-meaning environmental and other groups are attempting to tap into our natural self-interest. These services include resources like food, water, and wood, as well as processes like carbon sequestration and air purification. And there are cultural and aesthetic services – we value the serenity of nature, the beauty of tigers.

It’s OK to value organisms and ecosystems based on their benefit to us. It’s important to have a metric by which we can assess ecosystems’ values. If we were more rigorous about this, then we might have a better handle on the true cost of fossil fuels, meat, and Nikes.

But there are many species whose loss doesn’t mean much to us in an ecological, economic, or even aesthetic sense. If our ethic were to stop with the economic and environmental benefits to us, where would this leave critters like the desert pupfish? Why should we care? Because, beyond any value organisms may provide to us, they have intrinsic value, a right to exist. These creatures have evolved over hundreds of millions of years, and to just snuff them out in a blink just ain’t right. Each is an incredibly detailed, intricate, refined creation of evolution.**

But extinction is a natural part of life on Earth, you say. Yes, but humans have brought a chainsaw to this delicate natural surgery, with species loss probably over a thousand times higher than the natural rate of extinction (and with climate change underway, this will likely accelerate). By many accounts, we are in the midst of the sixth major extinction event on Earth, and it’s our fault.*** We need an ethic that goes beyond human self-interest, a refined ethic, a return to a greater appreciation of nature.

Aldo Leopold argued for a land ethic:

“The land ethic simply enlarges the boundaries of the community to include soils, waters, plants, and animals, or collectively: the land…. [A] land ethic changes the role of Homo sapiens from conqueror of the land-community to plain member and citizen of it. It implies respect for his fellow-members, and also respect for the community as such.”

Understanding that we are part of the greater whole, and valuing all its parts for their intrinsic worth, not only redounds to our economic and environmental benefit, it reconnects us, as humans, to the natural world. This is an essential component of living a fulfilled life.

On this centennial anniversary of the death of the last of one of nature’s spectacular creations, perhaps we should reflect on what we’ve wrought, and what kind of future we want to leave for posterity. In the words of Aldo Leopold, memorializing the passenger pigeon:

“We grieve because no living man will see again the onrushing phalanx of victorious birds, sweeping a path for spring across the March skies, chasing the defeated winter from all the woods and prairies of Wisconsin. …[A] few decades hence only the oldest oaks will remember, and at long last only the hills will know.”****



*Here are a few more, from Science.

**Of course, there are certain beings that I – selfishly, from a human point of view – wouldn’t mind seeing fully eradicated (the Ebola and AIDS viruses come to mind). And I wouldn’t go as far as Tolstoy, who apparently wouldn’t even kill a fly. Although it’s worth something to reflect upon what an amazing creature a fly is as we swat the crap out of it for waking us with its annoying buzzing.

***See the recent book by Elizabeth Kolbert, The Sixth Extinction, or The Sixth Extinction by Richard Leakey and Roger Lewin, or The Sixth Extinction by Terry Glavin.

****What if we could bring things like the passenger pigeon back from the dead? Here’s a paper discussing the ethics of de-extinction.

Update: For those interested in the idea that an accounting of ecosystem services may not be the best way to preserve biodiversity, a new paper in Science by W. M. Adams discusses some of the costs and benefits of this approach, concluding: “ecosystem service values are just one argument for the conservation of nature.”

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