Ever since Al Gore began raising awareness of global warming with his PowerPoint presentation and release of “An Inconvenient Truth,” numerous dramatic predictions about the effects of climate change have permeated the public consciousness. Hurricanes will ravage the Eastern Seaboard with increasing intensity and frequency. Rising sea levels will wash away Shanghai, forcing the evacuation of millions.
Unfortunately, the current discussion of global warming is rarely placed in the context of an even more arresting prediction: If current environmental trends continue, half of the species on Earth – perhaps including humans – will go extinct by century’s end.
OK, I know that sounds like scare mongering but stick with me for a moment.
The average lifespan of a species is about 100,000 years, so with an estimated 10 million species currently on Earth, we expect a certain number of species to wink out of existence each year. However, biologists widely believe the current extinction rate to be 100 times greater than the baseline rate, and eminent Harvard biologist Edward O. Wilson estimates a factor of 1,000 to 10,000. You could hardly be blamed if you didn’t notice, but we appear to be living through the fastest of the six episodes of mass extinction that have taken place in the Earth’s history. (Yes, incredibly, extinctions are taking place faster now than they did after an asteroid wiped out the dinosaurs.)
Unlike the five previous mass extinctions, this one is man-made. And as you may have inferred, global warming contributes significantly to current extinction episode. Biodiversity – that is, the diversity of life in a particular region – is on the downswing across the world in part because of the industrialization and attendant rise in carbon dioxide emissions that have taken place in the last two centuries. The International Panel on Climate Change, the world’s leading authority on global warming, wrote in a 2002 report, “Many of the Earth’s species are already at risk of extinction due to pressures arising from natural processes and human activities. Climate change will add to these pressures especially for those with limited climactic ranges and/or restricted habitat requirements.”
As the Earth grows hotter, species will gravitate toward the poles in search of cooler climates. Those unable to drift away from the equator fast enough – and there will be many – will face extinction.
However, other types of human activity, such as habitat destruction (for example, cutting down rainforests to create farmland) and the introduction of non-native species into different ecosystems, are more responsible for the extinctions than global warming.
For example, one of the most ignored aspects of the controversy surrounding the construction of a fence along the United States-Mexico border is the environmental impact the fence would have. Ecosystems cannot be sustained if they are internally divided, and many species’ survival depends on maintaining their particular migration patterns. A border fence would fail the environment on both counts, possibly causing the extinction of endangered species such as the jaguarondi and the ocelot as they are cut off from the Rio Grande. Though it seems like a barren wasteland, the desert is actually a fragile and highly diverse ecosystem, and small changes could radically alter it over time.
The biodiversity crisis isn’t just some fringe theory. A 1998 nationwide survey by the American Museum of Natural History found 70 percent of biologists believe “we are in the midst of a mass extinction of living things, and that this loss of species will pose a major threat to human existence in the next century,” according to a museum press release.
The reasons why the extinctions are a threat to humans should be self-evident, but experts believe averting the worst effects will require conservation projects on a scale far greater than anything ever undertaken. Simply creating and maintaining nature preserves circumscribed by developed land may not be good enough. Large ecosystems fragmented by man-made dividers like interstate highways will have to be reconnected to allow the free movement of life that is critical to preserving biodiversity.
All this suggests the question: Why is most of the public unaware of the “Sixth Extinction,” and why aren’t people panicking in the streets?
I don’t purport to know the answer, but I have a few suggestions.
Perhaps most importantly, the idea that mass extinctions are taking place is so wildly at odds with our daily encounters with nature that it would deserve to be dismissed without a shred of evidence but for the niggling fact that it’s true. Most of what’s going on takes place outside our immediate observation and is therefore easy to take lightly or ignore. We don’t see deer keeling over en masse and birds falling out of the sky – at least not yet. Biologists estimate they have discovered only about 10 percent of the Earth’s species, perhaps less, so most of the life on this planet is small and remains hidden to us.
A second explanation is that all other doomsayers throughout history predicting catastrophes that threaten the survival of humanity, from the Millerites to the Millenialists, have been proved wrong every single time; after all, we’re still here. In the late 18th century, Thomas Malthus contended that overpopulation would eventually lead to large scale famine, a hypothesis famously resuscitated by Nobel laureate Paul Ehrlich in his 1968 book “The Population Bomb,” which predicted Malthus’ nightmare would unavoidably come to pass within a generation. As it turns out, many European countries now face the opposite problem of too-low birth rates. Then just a few years ago there was the fear the Y2K bug would cause consumer electronics to go haywire and eat our mothers.
Any extraordinary claims about threats to our survival as a species should elicit a healthy amount of skepticism, and the biodiversity crisis is no different. Biologists acknowledge that research involving extinction rates is hampered by the difficulty of making direct observations of the majority of life on this planet, and their estimates carry a high degree of uncertainty.
However, arguments about the precise magnitude of the extinction rate should not distract from the central truth human activity has drastically altered the environment in a way that threatens to dramatically change the nature of life on this planet. And when a majority of biologists tell us that the biodiversity crisis will wipe out half the species on Earth within a couple of generations, it’s a sign that we should listen urgently.
Senior, College of Arts and Science.