We live in what is paradoxically a great age of discovery and also of mass extinction. Astonishing new species turn up daily, as new roads and new technologies penetrate formerly remote habitats. And species also vanish forever, at what scientists estimate to be 100 to 1,000 times the normal rate of extinction.
Over the past few years, as I was working on a book about the history of species discovery, I often found myself coming back to a fundamental question: Why do species matter? That is, why should ordinary people care if scientists discover one species or pronounce the demise of another?
It may seem too obvious to need asking. In certain limited contexts, people clearly do care. We will go to great lengths to protect a boutique species like the giant panda, for instance. We also thrill to the possibility of finding the slightest microbial hint of life in outer space, hardly blinking when the U.S. government spends $7 billion a year largely for that purpose. Meanwhile, we spend pennies exploring the alien life forms that are all around us here on Earth.
Maybe it’s just human nature not to value — or even see — the thing that’s right in front of our faces. And maybe it’s also a failure of communication.
We need to understand that our lives depend on species we have never heard of.
That is, scientists may need to explain their work on a far more basic level — not “Why do species matter?” but “Is food important to you?” or “Do you want your children to have effective medicines when they get sick?” or even “Do you like to breathe?” None of these questions overstates the importance of species.
For instance, Prochlorococcus is an ocean-dwelling genus of cyanobacteria and among the most abundant life forms on Earth. Why should we care? Because it produces about 20 percent of the oxygen we breathe — and yet until an MIT microbiologist named Sally Chisholm discovered it in 1986, Prochlorococcus was unknown. We need to understand in short that our lives depend on species most of us have never heard of — species we otherwise tend to shrug off as obscure, trivial, even undesirable.
Vultures, for instance. When we cause a species to go into decline, we almost never know — and hardly even stop to think about — what we might be losing in the process. In truth, it may be hard to think about, because the cascading effects of our actions are sometimes freakishly distant from the original cause. So in India in the early 1990s, farmers began using the anti-inflammatory drug diclofenac for the apparently worthy purpose of relieving pain and fever in their livestock. Unfortunately, vultures scavenging on livestock carcasses accumulated large quantities of the drug and promptly died of renal failure. Over a 14-year period, populations of three vulture species plummeted by between 96.8 and 99.9 percent.
A diversity of species can help prevent the emergence of new diseases.
Losing these efficient scavengers meant livestock carcasses often got left in the open to rot. It was one of those “ecosystem services” — manufacturing oxygen, soaking up carbon dioxide, preventing floods, taking out the garbage — that species generally provide unnoticed, until they stop. But the impacts went well beyond the stench, according to a 2008 article in Ecological Economics. Moving into the niche vacated by the vultures, feral dog populations boomed by up to 9 million animals over the same period. Dog bites and the incidence of rabies in humans also increased, and the authors conservatively estimated that an additional 48,000 people died during the 14-year period as a result. Calculating the bottom-line worth of what we get from the natural world is notoriously difficult. But even pricing lives at a fraction of developed world values, the near-total loss of three insignificant vulture species has so far cost India an estimated $24 billion.
A diversity of species can also help prevent the emergence of new diseases, though we tend to blame, rather than credit, nature for this particular ecosystem service. We sometimes respond to Lyme disease, for instance, by trying to kill the major players, blacklegged ticks and white-footed mice. But the “dilution effect,” proposed by Rick Ostfeld at the Cary Institute of Ecosystem Studies, suggests counterintuitively that having the broadest variety of host species in a habitat is a better way to limit disease. Some of those hosts will be ineffective, or even dead ends, at transmitting the infectious organism. So they dilute the effect and keep the disease organism from building up and spilling over to humans. But when we reduce biodiversity by breaking up the forest for our backyards, we accidentally favor the most effective host — in this case, the white-footed mouse. And we free the undiluted disease organism to operate at full strength.
The implications go well beyond Lyme disease. Around the world over the past half-century, researchers have tracked about 150 emerging infectious diseases, from Ebola to HIV, with 60 to 70 percent being zoonotic — that is, transmitted from animals to humans. “The question,” says Aaron Bernstein, a Harvard pediatrician and co-editor of the 2008 book Sustaining Life: How Human Health Depends on Biodiversity, “is whether humans are doing something to make these zoonotic diseases come out of the woodwork.” Clearly, we are doing a lot of one particular thing — knocking down forests and creating species-poor habitats with no “dilution effect” in their place. Thus the fear is that many more such epidemics may lie ahead.
And yet the value of even big, charismatic species remains so poorly understood that a Rutgers University philosopher writing in The New York Times recently proposed gradually wiping out cruel carnivorous species and replacing them with gentle vegetarians. He was upset that lions do not lie down with lambs, except to eat them for dinner. And he was apparently oblivious to the larger cruelty called a trophic cascade: Loss of predators strips a habitat of its diversity and leaves behind the animal equivalent of the civil service, or what writer David Quammen has called “a pestilence of minor nibblers.”
Our understanding is too primitive to say one species is important and another isn’t.
For instance, in the rocky world between high and low tides on the Pacific Coast near Seattle, the food chain (or trophic community, from the Greek trophikos, or nourishment) consists of barnacles, limpets, chitins, anemones, and particularly mussels. Starfish are the dominant predator. So mussels normally crowd up along the high tide line, where starfish are less likely to chomp them. In one study, a biologist removed the starfish to see what would happen. The mussels soon crept down toward deeper water, crowding out other species. Within a few years, only eight of the 15 original species still lived in that neighborhood. For all their apparent cruelty, killer species can be a means of fostering biodiversity.
So do individual species matter? Or is it just the diversity of species? The truth is that our understanding of the natural world is far too primitive for anyone to say one species is important, and another isn’t. In fact, scientists don’t even have names for most species; they’ve described only about 1.8 million of them, with an estimated 10 to 50 million still to go. So instead of waging pitched battles for individual species, conservationists in recent years have prudently tended to emphasize diversity, working to protect large swaths of habitat for a multitude of species. It’s the motorcycle mechanic’s approach to conservation, as articulated by Aldo Leopold: “To keep every cog and wheel is the first precaution of intelligent tinkering.”
But that should not stop us from trumpeting the benefits to humanity from individual species that might otherwise get written off as worthless, or even as impediments to human progress. Some conservationists may cringe at the thought of cheapening the natural world by defending it in economic terms. But NASA manages to hold onto a sense of wonder about its mission while simultaneously touting the idea that space exploration can pay for itself in technology transfers to the civilian world. (There’s actually a NASA “spinoff coloring book.” It celebrates an outer space mirror-polishing technology now also used to make ice skates go “super fast!”) The difference is that the spinoff argument for exploring species here on Earth is far more persuasive.
Species are a mother lode of material for making agricultural crops more productive.
The yew, for instance, was until recently a “trash tree,” says David J. Newman of the National Cancer Institute; he figures it was last valued around the time his ancestors used it to fashion bows for firing arrows at the Battle of Agincourt. But it’s now the source for taxol, relied on by tens of thousands of people as a life-saving treatment for breast, prostate, and ovarian cancers. Sales topped $1.6 billion last year, according to IMS Health, a healthcare information and consulting company. Likewise, no one ever marched to save the gila monsters, but their venom is the source of a new drug for people who resist conventional treatments for Type 2 diabetes, an epidemic disease now on track to affect more than a third of all Americans over their lifetimes.
In fact, the common idea that drug companies can cook up their medicines out of thin air through “rational drug design” in the laboratory is simply wrong. One recent study looked at more than 1,000 drugs approved worldwide over a 20-year period and found not one that was traceable to a totally synthetic source. Getting our ideas from species in the natural world is still the rule.
Likewise, wild species continue to be the mother lode of genetic material for making agricultural crops more productive, or more resistant to pests, disease, and drought. That kind of bio-prospecting is likely to become far more important over the next few years as biologists begin to explore the bacteria, fungi, and other microbial life forms that help plants do what they do. In fact, we will have little choice but to find smarter ways of exploiting the hidden resources of the natural world. If NASA in its glory years had a mission — to get to the moon in 10 years — biologists now have one, too: To sustain the species and habitat here on Earth that will be essential to providing food, medicine, and sanity as the human population grows to 9 billion people over the next 40 years.
There is one final argument for the value of species, and it has to do with beauty, biophilia, and a sense of the sacred. In the course of researching my book on species discovery, it seemed to me that one young 19th-century specialist in marine mollusks made the case most persuasively. In pursuit of new species along the coast of Alaska, naturalist William T. Dall experienced all the usual adventures, among them a long frigid trip in a sealskin dory across open water, trying to avoid being crushed by waves loaded with cakes of ice.
He gave his family an eloquent explanation of what motivated him, and by extrapolation most other species seekers: “There is a singular delight,” he wrote home in 1866, “in taking these delicate and almost microscopic animals and putting them under a strong glass, seeing the tiny heart beat, and blood circulate and gills expand, counting the muscles and blood vessels and almost the tiny disks that form the blood and to know that you are the first that has penetrated these mysteries and are perhaps the only one who ever will, and that all your notes and drawings and observations are so much solid knowledge added to the power and grace and beauty of the Infinite.”