Praise the Humble Dung Beetle

Lowly bugs, spiders and mollusks are more critical to ecology than larger, glamorous mammals.

Nothing against polar bears, which Sacha Spector loves as much as the next biologist, but to really get him going you need to ask about beetles. Specifically, dung beetles, whose disappearance would undoubtedly leave less of a void in our collective heart than the polar bear's but would rip a bigger hole in the web of life. Without the dung beetles that roam America's rangelands and pastures, animal droppings would not get rolled up and buried.

Seeds in the droppings would not get dispersed. Populations of parasites and disease-carrying pest species such as flies, to which the raw droppings on the ground are like condos with MOVE RIGHT IN! signs, would explode. Nutrients in the waste would be washed away rather than returned to the ground. Spector, who runs the invertebrate program at the Center for Biodiversity and Conservation at the American Museum of Natural History, could go on, but you can tell from his voice that he knows he's fighting a losing battle. Getting people to care about the 238 species of spiders, clams, moths, snails, isopods and other invertebrates on the list of endangered species is about as likely as a magazine putting a photo of a dung beetle rather than a polar bear on its cover.

Of all creatures great and small, it is the charismatic megafauna—tigers and rhinos and gorillas and pandas and other soulful-eyed, warm and fuzzy animals—that personify endangered species. That's both a shame and a dangerous bias. "Plants and invertebrates are the silent majority which feed the entire planet, stabilize the soil and make all life possible," says Kiernan Suckling, cofounder of the Center for Biological Diversity. They pollinate crops and decompose carcasses, filter water and, lacking weapons like teeth and claws, brew up molecules to defend themselves that turn out to be remarkably potent medicines: the breast-cancer compound taxol comes from a yew tree, and a leukemia drug from the rosy periwinkle. Those are tricks that, Suckling dryly notes, "polar bears and blue whales haven't mastered yet."

Since the lesser beasts of the field can't just muscle their way to survival, they tend to have talents that higher ones—with more brains as well as brawn to draw on—don't. As a result, they're loaded with gizmos that human engineers are tapping for inspiration. The Namibian beetle, for instance, has tips on the bumpy scales of its wings that pull water from fog, a design that has inspired a fog-harvesting net (it's used in cooling towers, industrial condensers and dry farming regions). The spiral in mollusk shells, which fluids flow through especially smoothly and efficiently, has inspired a rotor that draws up to 85 percent less energy than standard fans and is finding its way into computers and air conditioners. Biologists are cloning mussel proteins to produce an epoxy, mimicking the bivalves' ability to stick to rocks, that is expected to rival any superglue on the market. The American burying beetle, which feeds on carrion, can smell death from afar. "It can find a dead mouse [which it eats and feeds, regurgitated, to its offspring] within an hour of its demise from two miles away," says Quentin Wheeler, director of the International Institute for Species Exploration at Arizona State University. "Think of the potential if we could mimic that for finding earthquake victims."

Biologists draw an analogy between ecosystems and airplanes. The latter can fly without some of their rivets, and the former can survive without some of their species. But in neither case can you tell how many, or which ones, are dispensable until the thing crashes. "Some 99.99 percent of spe- cies that ever existed have disappeared, and nature moves on," notes Wheeler. "But you can never predict what the consequences will be in the short term, especially for humans who rely on the services that invertebrates provide." But after a species' numbers plummet, the effects haven't been pretty. For instance, as freshwater mussels have declined (70 percent of their species are threatened or endangered), taking with them their filtration services, water quality in streams, rivers and lakes has deteriorated badly. In the Chesapeake Bay, each adult oyster once filtered 60 gallons of water a day, packaging sediment and pollutants into blobs that fell harmlessly to the bay floor. Before the population crashed in the 1990s, oysters filtered 19 trillion gallons—an entire bay's worth—once a week. The survivors struggle to do that in a year. The result is cloudy, more polluted water, and a loss of fisheries and baymen's livelihoods.

The value of creepy-crawlies is not reflected in which creatures are protected by the Endangered Species Act, and this one isn't the Bush administration's fault. Like the rest of us, scientists gravitate toward the huggable. The upshot is that much less is known about invertebrates, including whether they're in danger of extinction, than about mammals. "With 57 insect species on the endangered list, out of 90,000 in the U.S., either there's something unbelievably resilient about insects or we're off by an order of magnitude in how many are in trouble," says Spector.

If Earth's species are a living library, then polar bears and other cuddly mammals are the best-selling beach reads. Everything else is the volumes of history and literature and other scholarship, written in the alphabet of DNA: 99 percent of all animals are invertebrates. To understand the history and the majesty of life requires reading, and thus preserving, those volumes.