How many species are there on earth?
Roughly between 1.5 million and 1.8 million have been discovered and given a formal scientific name.
While no one has yet made an accurate census from taxonomic accounts published over the last three hundred years, such an undertaking would undoubtedly represent only the tip of the iceberg.
Expert estimates range from 3.6 million to over 100 million, depending on the methods used. The median of the estimates is a little over 10 million.
Even these expert estimates are, at best, educated guesses – as illustrated by their vast disparity.
The truth is that we have only just begun to explore the marvels of life on earth.
In citing some examples of how little we know, I would like to paraphrase Edward O. Wilson from his eloquent 2002 state of the nation on biodiversity The Future of Life [a wonderful starting point for anyone who wants to start to share in the contemporary reality of the planet we call home]:
While 69,000 species of fungi (a kingdom of life that has thus far yielded numerous antibiotics including penicillin and ciclosporin that have altered forever the quality of human life) have been identified and named, as many as 1.6 million are thought to exist.
Nematode worms are thought to account for four of every five animals. Approximately15,000 have been identified, and millions are thought to exist.
Our blue oceans swarm, at the microscopic level as at the macroscopic level, with little known forms of life. Research in the 1990’s revealed that oceanic bacteria, protozoans and archaeans are much more abundant and diverse than we ever could have imagined. The visible organisms of the ocean represent only the apex of a vast and complexly interdependent interweave of biodiversity.
Another frontier is the ocean floor, which constitutes 70 percent of the earths surface. All thirty-six known animal phyla (highest ranking taxonomic sub-group within the animal kingdom) exist in the ocean environment, as opposed to ten on land. Two have been discovered in the last 30 years, with the deepest parts of the oceans still relatively unexplored.
Even the most familiar organisms are less studied than might be guessed.
About ten thousand species of ants are known to date, and this figure is expected to double as tropical regions are more extensively surveyed.
The global number of documented amphibians grew by almost one-third between 1985 and 2001.
Even new mammals are being discovered at a considerable rate. Fueled by improved technological and biological capabilities and by the urgency of vanishing ecosystems, renewed interest in the field on taxonomy continues to yield an astonishing number of new species, vertebrate and invertebrate, every year.
Many amazing accounts of biodiversity continue to pour in from the tropical rain forests of the world, where more than half planet’s plant and animal species are thought to reside. Says Wilson: “425 kind of trees in a single hectare of Brazil’s Atlantic Forest, for example, and 1300 butterfly species from a corner of Peru’s Manu National Park. Both numbers are ten times greater than those from comparable sites in Europe and North America. The record for ants is 365 species from 10 hectares in a forest tract of the upper Peruvian Amazon.”
While such richness is concentrated in these areas and remains largely unrealized, wealth in biodiversity is by no means exclusive to such ecosystems. Wilson elaborates:
“A single coral head in Indonesia can harbour hundreds of species of crustaceans, polychaete worms, and other invertebrates, plus a fish or two. Twenty-eight kinds of vines and herbaceous plants have been found growing on a giant Podocarpus yellow-wood conifer in the temperate rainforest of New Zealand…. As many as two hundred species of mites…teem in a single square meter of some hardwood forests of North America. ….
….You yourself are a rainforest of a kind. There is a good chance that tiny spider-like mites build nest at the base of your eyelashes. Fungal spores and hyphae on your toenails await the right conditions to sprout a liputian forest. …. Every time you scuff the earth or splash mud puddles with your shoes, bacteria, and who knows what else, that are still unknown to science settle upon them.
Such is the biospheric membrane that covers Earth, and you and me. It is the miracle we have been given. And our tragedy, because a large part of it is being lost forever before we learn what it is and the best means by which it can be savoured and used.”
How many species are there? Now that I know that we have no clue, I would like to hazard a guess.
My guess is that there is one species that holds in its hands the power to preserve at least a portion of the majesty that existed before the industrial revolution and population explosion. Now that we are conscious of (or at least have a scientifically irrefutable inkling) the impact of our energy and economic systems on the very planet that sustains us and still offers us abundance in exchange for due diligence and the responsibility of custodianship that we have created for ourselves.
So what can we do? Well, to curb the strain of the population explosion on global resources, we can start by not having kids, or by not having any more kids, or by adopting, or by having just one.
And this paper from the International Union for Conservation of Nature would be a good place to start to get a sense of where we are now.