Another Life: All creatures great and small are getting harder to discover
From elephants and giant squid to tiny mites and microbes, how many species live on Earth? Does it matter more to find out all there are, in the hope of conserving more of them, or to try to protect those we already know about?
Dux redux: the giant squid has its own Darwin Centre tank. Illustration: Michael Viney
‘All things bright and beautiful / All creatures great and small / All things wise and wonderful / The Lord God made them all.”
It was a great tune for piping in my Anglican infants’ school, but I don’t think it made me much of a creationist, even then. Some sense of the great infinitude of life does, however, radiate from current argument about the planet’s species. From elephants and giant squid to tiny mites and microbes, how many are there, really? Does it matter more to find out all there are, in the hope of conserving more of them, or to try to protect those we already know about?
About 1.75 million species have already been identified, but how many more organisms remain to be found and named? Estimates by scientists of nonmicrobial life range from two million to more than 50 million species, with large remaining uncertainties about the numbers of terrestrial insects and deep-sea invertebrates. Scientists name new species all the time. But as human destruction of habitats gets worse, are Earth’s species being extinguished faster than they can be discovered and described?
A leader among optimists is Dr Mark Costello, an academic at the University of Auckland, in New Zealand, who trained as a marine biologist in Galway and Cork and later did research at TCD. He led the BioMar project that mapped life around Ireland’s coasts, is an authority on sea lice at salmon farms and, from New Zealand, led the summary report of the Census of Marine Life, finalised in 2010. This was the decade-long scientific effort that added more than 6,000 species from the oceans of the world.
Costello commands attention, therefore, in claiming that “with just a modest increase in taxonomy and conservation most species could be discovered and protected from extinction.” In a paper published last spring, he and his colleagues supported the proposition that two-thirds of all species have now been named and that new ones are getting harder to discover. About 17,000 are added each year, so quite a small boost to effort should find the rest – to a planetary total, he thinks, of perhaps three million species. As he points out, a good many of the undiscovered are likely to be lurking in known biodiversity “hot spots” of the tropics.
Taxonomy goes back for centuries to the seeming human need to put a name on everything in nature. The great Swedish naturalist Carl Linnaeus (1707-1778) brought order to a chaotic improvisation by classifying nature into kingdom, class, order, family, genus and species. He also boiled down the name of a species to two Latin words, the first putting the organism into its genus, the second allotting its specific name. At its best, the name expresses something of the form of the plant or animal, as well as its affinity with others of its kind or a particular sort of habitat.
This system sustains the great collections of species held in the museums and science centres of the world. At our National Botanic Gardens, for example, the herbarium holds more than 500,000 “dried and documented” plant specimens from Ireland and the rest of the world. In the Darwin Centre at the Natural History Museum in London, 22 million specimens in bottles fill 27km of shelves. (The colossal giant squid, Architeuthis dux, gets a spirit tank of its own.)
Taxonomy has moved on from simple fieldwork and physical description. High- throughput DNA sequencing promises faster, more systematic identification of species. But the suggestion in 2003 of a new “DNA taxonomy” updating or replacing the Linnaean system has led to worried responses from evolutionary biologists and others. Defining species by a DNA barcode rather than a systematically distilled Latin name is a prospect unsettling to many. And sampling the DNA of specimens could certainly winnow their number of a good many duplicates and confusions.
The debate has helped nourish a widespread view of taxonomy as an outmoded science unable to cope with the biodiversity crisis and served by a declining and underfunded body of biologists. There are claims, however, that taxonomists have been rapidly increasing. Costello’s team has discovered three times more people naming species than there were before. “We’re in the golden age of taxonomy,” he says.
He’s all for this, and for expanding the role of ordinary nature-lovers in finding and reporting species. But he also wants better co-ordination and coherence in the international taxonomic community. He likes to point out that, even in the Linnaean scheme of things, the sperm whale has, at various times, been given 19 scientific names.
Even so, I suspect, he would be happier to live with Physeter macrocephalus, “the great-headed blower of vapour”, than a string of biochemical code that might have been typed by a chimpanzee.