We just do not know how many different species live on earth, according to a new study by a group of international scientists.
“There could be as few as two million species or more than 50 million,” said Professor William Laurance of James Cook University. “That’s how uncertain things are.”
Professor Laurance is co-author of the study published in in Trends in Ecology and Evolution.
“Some groups of species—such as plants and birds—are well-known, with scientists discovering relatively few new ones each year,” he said.
“But it is almost impossible to guess how many unknown species of insects and fungi there are.”
Lead author Brett R. Scheffers of National University of Singapore said that what was known was that the unknown species were likely to be living in places where they are in danger of extinction.
“We could lose many of them before we realise how valuable they are,” he said.
The study suggests that many of these species are important for medicine, water purification and provide numerous other services for humanity.
For example, cone snails, which are especially abundant on the Great Barrier Reef, are enormously important for drug development ranging from pain-killers to treatment of neurological diseases.
“Many species of these snails are newly discovered and many more await discovery,” Professor Laurance said.
“We simply can’t afford to lose these species because of neglect and short-sided economic gains,” he said.
Laurance, Scheffers and their colleagues summarise the answers to what may seem like straight forward questions about the Earth’s biodiversity but they warn “these answers are deceptively complex."
Their report collates information from numerous studies that attempt to estimate numbers and characteristics of unknown biodiversity.
Another co-author, Dr Lucas Joppa at Microsoft Research in Cambridge, UK said that “many missing species are hard to find, such as deep-sea organisms, high mountain species or those that live underground.”
Missing species are believed to often be small in size and living in small geographic areas, such as high-elevation rainforests in the Wet Tropics of north Queensland.
The authors stress that some major challenges complicate the species-description process. Sometimes two different species are accidentally assigned the same name, or there are animals that look nearly identical and therefore can only be identified by genetic analyses.
Although these challenges present real struggles for future biodiversity inventories, the report stresses that progress is being made.
“New technologies such as environmental DNA analyses can detect a species presence from mere water samples without our ever seeing it,” Mr Scheffers said.
“The crazy thing about all this is that we could have way more than 50 million species if we start counting microbes such as bacteria, viruses and the like,” Professor Laurance said.
“It just shows how much we still have to learn about the diversity of life on Earth.”