We don’t know the number of species on Earth. Estimates go into the tens of millions with about 1.4 million having been described.
- 750,000 are insects
- 250,000 are higher order plants (flowering plants)
- 4,000 are mammals (human beings being one of these)
Listen to E. O. Wilson in The Diversity of Life:
The immense diversity of the insects and flowering plants combined is no accident. The two empires are united by intricate symbioses. The insects consume every anatomical part of the plants, while dwelling on them in every nook and cranny. A large fraction of the plant species depend on insects for pollination and reproduction. Ultimately they owe them their very lives, because insects turn the soil around their roots and decompose dead tissue into the nutrients required for continued growth.
And this is the basis of human life as well.
So important are insects and other land-dwelling arthropods that if all were to disappear, humanity probably could not last more then a few months. Most of the amphibians, reptiles, birds, and mammals would crash to extinction about the same time. Next would go the bulk of the flowering plants and with them the physical structure of most forests and other terrestrial habitats of the world. The land surface would literally rot. As dead vegetation piled up and dried out, closing the channels of the nutrient cycles, other complex forms of vegetation would die off, and with them all but a few remnants of the land vertebrates. The free-living fungi, after enjoying a population explosion of stupendous proportions, would decline precipitously, and most species would perish. The land would return to approximately its condition in early Paleozoic times, covered by mats of recumbent wind-pollinated vegetation, sprinkled with clumps of small trees and bushes here and there, largely devoid of animal life. [emphasis mine]
From a review by Aaron Segal.
The case for preserving maximum biodiversity is made on firmly utilitarian grounds. “Biodiversity is our most valuable but least appreciated resource.” Wild species contribute to hybrid, resistant food crops, to critical pharmaceuticals and to hosts of other benefits to humans. Yet our knowledge of biodiversity barely scratches the surface and each extinct species represents a permanent loss of knowledge and value.
The Diversity of Life by Edward 0. Wilson
The Belnap Press of Harvard University, 1992
Paperback reissue edition: W. W. Norton & Company, 1999
ISBN-10: 0393319407
ISBN-13: 978-0393319408
update: The people doing the Catalog of Life think there are about 1.75 million known species.
I’m not sure that a world without insects is remotely possible nor useful in addressing biodiversity. This is simply more fear mongering. Mamals are by far the most threatened group, given their relative lack of diversity compared to insects.
I do agree though that biodiversity is important in maintaining a healthy environment.
Would you consider genetic engineering as a form of artificial biodiversity?
Fear mongering was not my intent, Brendan. I thought the passage was an eloquent description of interdependence within the web of life. In the same way you can think about the importance of air, water, or food by imagining how long you can survive without one of those, Wilson gives us three months if the insects were to disappear — and not just us but all higher terrestrial forms.
I liked his other point in that chapter as well: we know of perhaps 10% of all the species on the planet. We can’t even measure how much of the 90% might be going missing and what the impact of that might be.
Yes, genetic engineering is a form of artificial biodiversity — with all the word artificial entails.
Nice post. I’ve hears people question whether species loss is really hapening at any sort of unusual rate. But references from qualified scientists to rates of species loss at 100 to 1,000 times the normal background level are now common:
http://www.americanscientist.org/template/AssetDetail/assetid/14434
An estimate I came up with a while back was 27 species per day, based on 1,000 species per million lost per year, and a conservative estimate of 10 million species:
http://www.sciencemag.org/cgi/content/full/297/5583/954
But as you point out, we really don’t know how many species there are, and we’re undoubtedly losing a great many with which we’re completely unfamiliar. We’ll never know what medicinal or other knowledge we might have gained from them. More importantly, as the web of life erodes further and further, we don’t know what cascading effects will occur at what points.
I didn’t see your post at fear mongering at all. In fact, I usually just read the phrase, “fear mongering” as a tactical propagandistic term rather than an attempt to seek truth, and move on.
Peter Raven’s speech to the American Association for the Advancement of Science (your sciencemag.org link) is quite eloquent.
Here’s an interview with him. Found the link here, an excellent blog by a philosopher of science who is “primarily interested in biology and its philosophical implications.”
We also don’t know the rate of new species creation. For the little critters it must be quite significant. And there is a lot of evidence that speciation increases as population numbers decline or become isolated. I’m inclined to agree with Brendan that the loss of larger animals is of most significance to humans principly for reasons of asthetics. We can survive without tigers or pandas but what a sad day it will be if we loose them.
The factoid I find fascinating is that a tree sucks itself into existance and builds it’s bulk using just air and water with only a few percent of it’s mass coming from the soil.
Here is a tough challenge for anybody that wants a little research task. Name ten species of animal that have been officially declaired extinct (by a reputable scientific body) during any year since 1997. WWF will frequently cite numbers like 40,000 per annum but my challenge is name just ten from the last decade. If you want it can be a group effort.
I do think the claim that the extinction rate is 1000 times historical levels is reasonably credible. And I agree it is a worry. Having cut down my garden a number of times now I am however pretty impressed with the way nature bounces back if you neglect it.
First of all, it should be made clear that many of the species that goes extinct are plants, not just animals.
In most cases, you can’t point to any specific years as when an animal goes extinct. For example, the Sinú Parakeet is thought to be extinct, since it hasn’t been observed in decades and wasn’t found during searches in 2004 and 2006.
Also, are we talking totally extinct, or are we talking extinct in the wild? Or functionally extinct?
The following species are extinct in the wild, but might still lives in captivity:
Wyoming Toad, Hawaiian Crow (a breeding program might save this species), the Mitu mitu, the Socorro Dove (less that 100 lives in captivity), Redwood, the Saudi Gazelle (there is some debate if it is a destinct species), Bastard Gumwood (last known wild tree was destroyed in a storm in 1986), Black Soft-shell Turtle (only lives in a pond near Chittagong, Bangladesh), Biznaguita (a plant discovered in 1991, believed to have died out during the severe freeze on Mexico’s Altiplano in December 1997), the Sahara Onyx (last reported observed in 1996, but hasn’t been found since), Ua Pou Monarch (bird species which hasn’t been observed even when searched for in 1998 and 1999), the Orange Toad (Bufo periglenes, not observed since 1989)
The following species are functional extinct:
Yangtze River Dolphin, Geochelone nigra abingdonii (Galapagos turtle species, with only one know survivor – “Lonesome George”)
Terje: I’m inclined to agree with Brendan that the loss of larger animals is of most significance to humans principly for reasons of asthetics.
I think this is a popular misconception. Summarizing E. O. Wilson:
The sea otter lives on the west coast of the USA and was hunted to near extinction for its pelt. This caused the collaspe of the kelp forests, because the otters preyed on sea urchins which eat kelp. “Large stretches of the ocean floor were reduced to a desert-like terrain, called sea-urchin barrens.” And it wasn’t just a loss of kelp but the whole ecosystem: algal species, crustaceans, squid, fishes, and others. Luckily some of the otters survived at either end of their range. Restoring them in between restored the whole ecosystem (mostly).
He goes on to describe other examples:
Losing the big cats of South America means their prey increase in number (by a lot). The prey eats more of the seeds they are fond of and that species of tree declines. The changes ripple outward across the food web changing the nature of the ecosystem.
Elephants push over, break, or uproot trees to get at their succulent branches creating a mosaic of habitats in their wake. Lose or reduce the numbers of elephants and you lose the habitats and the life dependent on them.
“It has become clear that an elite group of species exercises an influence on biological diversity out of all proportion to its numbers.”
[...] another. We see climate change, species extinctions rates as much as 1000 times normal (see the recent post on biodiversity at Trinifar), extreme overfishing of both the oceans and fresh water environments, [...]
Kristjan – My challenge was not to prove that a given set of animals became extinct in the last ten years. Merely to name ten that were “declared” extinct by a scientifically reputable body during the period. Of course this is merely an exercise for the purposes of generating some topical discussion. Does anybody want to get the ball rolling with just one name?
Trinifar – regarding the otter example. You are of course correct that an ecological system has complex inter-relationships and the removal of one species effects all manner of other things. I don’t disagree with this. However rather than seeing it as a frailty within nature I’m inclinded to view it as a form of resilient flexibility. Not that we should deliberately test it’s limits.
I found this interesting reading Extinctions in Recent Time, a chapter from a book by The World Conservation Union, also know as The International Union for the Conservation of Nature and Natural Resources.
Terje, did you notice the rather long list I gave. All of them are declared exstinct in the wild, exstinct or functional exstinct within the last ten years.
The Yangtze River Dolphin was decalred functionally exstinct (unable to be saved through breeding programs) just a few months ago.
Kristjan,
Your list includes few animals declared extinct in the last ten years. However I’m not trying to trivialise the extinctions that do occur. All I’m saying is that the observed rate is in the order of a few a decade. Not a heroic effort, probably well above the natural rate but not what the headlines tend to say either.
Regards,
Terje.
[...] again to E. O. Wilson in The Diversity of Life. The last two paragraphs of the book: The evidence of [...]
[...] (although still tragic amount) of suffering, and establish a truly civilized society that respects the diversity of life, universal human rights, the need to live under Earth’s human carry capacity, and the value [...]