The massacre of species at present rates has baleful consequences for Earth, writes Tim Radford
A big fish is about to swim away, forever. The barndoor skate, Raja levis, seems close to extinction.
In 1951 research ships found it in 10% of all trawls of the St Pierre Bank in the Atlantic Ocean off Newfoundland. Over the past 20 years, none at all have been caught there.
The barn-door skate grows to a metre across – not something you would miss if you were looking out for it. But nobody was.
Failure to examine historical data has resulted in the largest skate in the North Atlantic being driven to near extinction without anyone noticing, say researchers.
If something the size of a barn door could slip away without being missed, the fate of little-known species is likely to be worse.
The things that make life possible are barely visible. Laboratory experiments based on small, artificial worlds demonstrate that diversity is life’s strongest card.
The recycling of air and water and plant nutrients is the business of little creatures that most of us never notice.
The food we eat, the medicines we take and the tools we use have been fashioned for us by 500-million years of evolution. Yet we know practically nothing about most of them. We even lack a starting point.
Who knows how many small fry are being destroyed? Creatures are being erased from life’s register faster than anyone can record them. All the evidence is that humans are extinguishing other life forms on an epic scale.
But there are no tallymen to count the dead, or take the measure of the living: there are probably only about 7 000 experts – they are called taxonomists, or sometimes systematists – with the authority to distinguish species from one another. Most are in the wrong places and few have been getting much encouragement. Without them we cannot even begin to argue.
The book of Genesis established 3 000 years ago – to the satisfaction of Jewish and Christian Europe, at least – that man had dominion over beast and fowl. But it was not until 1758 that Carl Linneaus, the great Swedish taxonomist, began counting the kingdom. French and British natural historians followed and established a systematic way of interrogating a creature’s nature in order to make a family connection.
They started with kingdoms (is it animal or vegetable?); phyla (has it got a backbone or a skeleton on the outside and jointy legs?); class (is it a mammal or a marsupial?); family (can it walk upright?); genus (is it a human of some kind or a cat maybe?) and species (call that a sapien).
In the course of 240 years, they established a local habitation and name for each of about 1,8-million species.
But there is no central catalogue or inventory. So the same species might be recorded under one identity in one country and under a separate name in another.
Where scientists have checked, they have found “synonymy” in perhaps 20% of cases. So the true number of species that have been described and named is perhaps only 1,4-million.
Then researchers began to look a little harder. They spread nets under trees, dusted them with insecticide and counted just the arthropods (including insects) that fell.
The numbers astonished them. When they reached 50 000, they started to get alarmed: by that reckoning there might be 20-million species to be described, rather than two million.
What was true for the Amazon rainforest turned out to be equally true for coral reefs and mangrove swamps. The great plains of Africa turned out to be bewilderingly rich in life.
“Everybody’s idea of the Serengeti is a big acacia tree with a leopard hanging in it,” says one ecologist. But there are at least 28 species of acacia in the Serengeti.
God knows how many beetles there might be – and God, as the great biologist JBS Haldane once deduced, has “an inordinate fondness for beetles”, having made so many of them.
But taxonomists are oppressed by something darker than the task of counting. What is going on now is described, quite calmly, as “the sixth great extinction”.
The fossil record is a pattern of evolution and extinction, with species continuously evolving, flourishing and expiring as naturally as individuals are born, develop and die.
Imposed on this hubbub of appearance and disappearance is a series of dramatic happenings: mass disappearances, followed by new beginnings, at least five times in the past 500-million years.
The last of these was 65-million years ago, when a 10km asteroid whacked into the Yucatan in Mexico. The change now is less dramatic, but no less significant.
According to some theorists, half of all the creatures with which humans share the planet could be about to steal away into the eternal night, simply because their homes are being destroyed – by man.
The world’s dwindling tropical forests could be losing creatures at the rate of 27 000 a year – three creatures an hour – at the most conservative estimate. The precision of these figures is disputed, the truth behind them is not.
In the last century birds and mammals have been disappearing at an average rate of one a year. This is already a thousand times faster than the “background” rate of extinction.
It is confirmed by crude counts made by the conservation groups: a tenth of all flowering plants are about to disappear, a tenth of all birds on the planet are seriously endangered, many of the big mammal groups – the cats, in particular – could be about to disappear.
But 99% of creation is less than 3mm long. Most of the smaller species will be gone before scientists ever find out they were here.
So taxonomy’s high command – people at the Smithsonian and the Missouri Botanic Gardens in the United States, and the Natural History Museum in London and at Kew – decided to stake out small areas of forest or savannah and simply sample the local life with quick headcounts of this and that species.
Such a British project in the Cameroon came to an abrupt end only last year.
Scientists had marked out a few hectares of already well-studied forest and begun to catalogue all the creatures in just a limited selection of groups. They gave up. Even within the limits the scientists set, there were simply too many species to count.
“They absolutely overwhelmed the resources,” says John Lawton of the Imperial College in London and president of the Royal Society for the Protection of Birds.
“We could have carried on, but we would have needed many more taxonomists and systematists,” he said.
There’s the rub. “The global workforce, considered to number 7 000 systematists, is clearly inadequate, given the scale of these tasks,” says Stephen Blackmore, keeper of botany at the Natural History Museum.
Work done by taxonomists based in London or Washington essentially involves travel to faraway places on budgets that simply don’t stretch very far.
Good taxonomists don’t grow on trees. Lawton says: “Really good taxonomists will be able to identify on sight more than 10 000 species of their chosen group, without having to look anything up.”
There is a case for biodiversity: everybody recognises it. A landscape without skylarks or corn cockles is poorer.
But creatures disappear because their surroundings change, and those surroundings were maintained for them by other sets of creatures.
So biodiversity cannot be managed unless it can be understood, and it cannot be understood unless its components are identified.
Biodiversity is a matter of naked human self-interest. Human economy rests on plants. Crops and their wild relatives have to be understood and conserved and that means the insects that prey on them must also be understood.
Plants that provide most medicines – from aspirin for headaches to taxol for breast cancer – have developed the chemicals they possess as a response to their co-evolution with insects.
There could be billions of dollars of useful, valuable, exploitable knowledge to be gained from almost unknown creatures in their habitats.
Why do barnacles not grow on starfish? Because they secrete a natural anti- fouling paint.
Why do arctic fish not freeze? Because they have an antifreeze fluid to keep blood circulating.
Last year Cornell scientists calculated that if humans had to pay for the services they received free from nature – pollination, water purification, crop pest control, that sort of thing – the bill would be $2,9-million annually.
Fellow creatures are a kind of map of creation. “Just knowing how many species there are is like having proper maps of the stars,” says Lawton.
“It’s exactly the same for a proper science of ecology and evolution and many areas of biology. We need to know how many organisms there are, what they are and where they are.”