Are we in the midst of the sixth mass extinction?

[Nereid]

Over on the Politics & World Affairs sub-forum, in a thread called climate risk 'to million species'*, I asserted that the Earth is the midst of the sixth mass extinction**. There was some disagreement, so I suggested that we apply the scientific method, and test the assertion. More discussion, much agreement, ... and here we are.

So, my proposal:
1) We all agree on what constitutes a mass extinction.

2) Bystander and Russ propose a definition of the 'normal' or 'background' extinction rate; we discuss it and agree.

3) We agree on what the actual background extinction rate has been, up to 1mya.

4) I propose a means of estimating the present extinction rate; we discuss it and agree.

5) I will make an estimate of the present extinction rate; we discuss it.

Supplementary topic: if we agree that number six is in progress, then we look for causes.

Some other 'rules':
+ we establish our protocol before we begin the work; that's 1 through 5 above, plus these 'rules'
+ we restrict ourselves to peer-reviewed sources (which we post a link to, if possible)
+ I will try to keep us on track, and move us along to the next item when we're ready (I'm happy for someone else who we trust to take this role, if Bystander, Russ, Ivan or SelfAdjoint is uncomfortable with me taking it). Of course, Monique and Another God will keep us all honest

*Here's the thread:
https://www.physicsforums.com/showthread.php?s=&threadid=12280

As this may be new to the denizen of Biology, let's add a 0):
0) two days for questions, suggestions (on the protocol!), etc before we start.

**The widely accepted 'five mass extinctions' occurred at the end of the Ordovician, Devonian, Permian, Triassic and Cretaceous (bye-bye dinosaurs).

[Edit: fixed typo]

 

[russ_watters]

I'm not sure how exactly you plan to start, but do you have any info about those 5 mass extinctions? An account of them may help with #1.

 

[Bystander]

Second on the summaries. If someone would care to throw in a quick heirarchy of kingdom, ..., ..., family, genus, species, it'll save me enormous embarassment.

Re. "rates," might I suggest we look at four? "General rates for appearances/emergences and extinctions of wide-ranging/widely distributed species, and the same pair of 'pocket/isolated/enisled/marooned rates' for special environment cases, Lake Victoria, Galapagos, etc.?"

 

[selfAdjoint]

If we're going to look for a Great Extinction, we need

(a) total number of species existing at the start of whatever period we pick (Quaternary? Holocene? Post-Glacial? Last 25,000 years?)

(b) Count of species gone extinct during period.

(c) An agreed on figure (proportion of existing species gone extinct) that will constitute a Great Extinction.

As long as we refrain from over-hastily attributing cause, that should enable us to establish the fact or otherwise of the Sixth Great Extinction hypothesis.

I hope we can hold to the schedule laid out above by Nereid, and if we do I think we will have something trustworthy.

 

[Phobos]

Some big names in biology have addressed this...
http://www.well.com/user/davidu/sixthextinction.html
http://www.actionbioscience.org/newfrontiers/eldredge2.html

another related link...
http://www.nationalgeographic.com/ngm/9902/fngm/

 

[timejim]

Originally posted by Nereid
Over on the Politics & World Affairs sub-forum, in a thread called climate risk 'to million species'*, I asserted that the Earth is the midst of the sixth mass extinction**. There was some disagreement, so I suggested that we apply the scientific method, and test the assertion. More discussion, much agreement, ... and here we are.

So, my proposal:
1) We all agree on what constitutes a mass extinction.

2) Bystander and Russ propose a definition of the 'normal' or 'background' extinction rate; we discuss it and agree.

3) We agree on what the actual background extinction rate has been, up to 1mya.

4) I propose a means of estimating the present extinction rate; we discuss it and agree.

5) I will make an estimate of the present extinction rate; we discuss it.

Supplementary topic: if we agree that number six is in progress, then we look for causes.

Some other 'rules':
+ we establish our protocol before we begin the work; that's 1 through 5 above, plus these 'rules'
+ we restrict ourselves to peer-reviewed sources (which we post a link to, if possible)
+ I will try to keep us on track, and move us along to the next item when we're ready (I'm happy for someone else who we trust to take this role, if Bystander, Russ, Ivan or SelfAdjoint is uncomfortable with me taking it). Of course, Monique and Another God will keep us all honest

*Here's the thread:
https://www.physicsforums.com/showthread.php?s=&threadid=12280

As this may be new to the denizen of Biology, let's add a 0):
0) two days for questions, suggestions (on the protocol!), etc before we start.

**The widely accepted 'five mass extinctions' occurred at the end of the Ordovician, Devonian, Permian, Triassic and Cretaceous (bye-bye dinosaurs).

[Edit: fixed typo]

I think we are headed, soon, towards a new Earth and Heaven??

 

[Bystander]

More for the reading list: Google "david raup" + "extinction rate" and "michael foote" + "extinction rate" --- couple dozen sites for each. Raup took off on the "Nemesis" hunt after Alvarez pointed the world's attention toward catastrophism, but he did some decent analysis of "extinction events" along the way.

 

[Ivan Seeking]

http://web.clas.ufl.edu/users/morgans/Extinction2_Apr17.pdf
http://www.cyber.vt.edu/geol3604/Extinct.pdf

 

[Nereid]

King Phillip called out for good soup

Bystander wrote: Second on the summaries. If someone would care to throw in a quick heirarchy of kingdom, ..., ..., family, genus, species, it'll save me enormous embarassment.

Kingdom
Phylum (Division for plants)
Class
Order
Family
Genus
Species

Here's one readable overview:
http://www.wordiq.com/cgi-bin/knowledge/lookup.cgi?title=Class_(biology)

 

[Nereid]

Originally posted by russ_watters
I'm not sure how exactly you plan to start, but do you have any info about those 5 mass extinctions? An account of them may help with #1.

A range of sources, directed at a range of audiences:
http://www.bartleby.com/65/ma/massex.html
http://www.zoomdinosaurs.com/subjects/dinosaurs/glossary/Massext.shtml
http://www.bbc.co.uk/education/darwin/exfiles/massintro.htm
http://ethomas.web.wesleyan.edu/ees123/mass_extinctions.htm

 

[Andre]

A very creative hypothesis of Richard Muller is the relation between mass extinctions and the close encounters of a possible twin star Nemesis.

http://muller.lbl.gov/pages/lbl-nem.htm

Incidentely, a bit of a contrast, We may be in a mass extention phase indeed but not because of human actions. The events that constitute the Younger Dryas - Pre Boreal boundary 11,570 years ago, caused dozens of mega fauna species (mammots etc) to become extinct. In the mid Pleistocene, one million years to 600,000 years ago, I believe about a quarter of the oceanic foraminifea became extinct. It may have gone unnoticed by the public, but it got the oceanic biologists rather excited.

So whatever the Pleistocene has been doing to Earts biota, it may continue that way for millions of years more without the help of mankind. Palaeonthologists of hundreds of million years in the future may only recognise a single mass extinction.

On the other hand the explosion of evolution of some species in the past 10,000 years like the African Lake Malawi and Lake Victoria cichlids may compensate for the loss of other species and the total count of species may be still increasing.

And BTW, I don't think that this is science, rather hype forming propaganda:

http://news.bbc.co.uk/1/hi/sci/tech/3375447.stm

 

[Nereid]

Step 1: Agree on what constitutes a 'mass extinction'

Two days are up, no substantive suggested changes to the protocol (thanks for the support).

1) We all agree on what constitutes a mass extinction.

Which level(s) do we look at?
Kingdom, Phylum/Division, and Class may be too broad (few exist, very few - none? - have gone extinct in one of the big 5)

Species and Genus may be too narrow (how to count them all? make robust estimates?)

-> focus on Order and Family, with appropriate consideration of Class and Genus. Yes/No/Maybe?

Which environments do we consider?
Those which leave copious numbers of fossils (e.g. shallow marine) may be better than those which don't (e.g. alpine) Does it matter that we are somewhat equivocal in how we include some environments (e.g. tundra)? or some taxa (e.g. soft invertebrates, fungi, algae)?

I'd love to trace the (non-)extinctions of my namesakes, but I suspect there'll be little fossil data to use
http://www.pmel.noaa.gov/vents/nemo/explorer/bio_gallery/biogallery-Info.00054.html

 

[Ivan Seeking]

Originally posted by Nereid
-> focus on Order and Family, with appropriate consideration of Class and Genus. Yes/No/Maybe?

This seems to be consistent with the references.

Which environments do we consider? Those which leave copious numbers of fossils (e.g. shallow marine) may be better than those which don't (e.g. alpine) Does it matter that we are somewhat equivocal in how we include some environments (e.g. tundra)? or some taxa (e.g. soft invertebrates, fungi, algae)?

Why choose by environment? Is this intended to narrow the field for comparison?

 

[Bystander]

Originally posted by Nereid
1) We all agree on what constitutes a mass extinction.

Which level(s) do we look at?

Species (cross fingers, knock on wood) --- tough as that is in the fossil record.

Which environments do we consider?

Long as there is a continuous record before, through, after the event(s) we examine (major extinctions), I'd say look at whatever we can get our hands on, characterize it as sampling some "environment type" during an extinction event, and see if my hypothesis that there ain't no Lakes Malawi, Victoria, Tanganyika, Hawaiian chains, Galapagos, or Andean ridge ecologies showing up in the fossil record holds any water.

 

[Nereid]

Ivan asked: Why choose by environment? Is this intended to narrow the field for comparison?

Primarily to ensure there's a big enough base from which to calculate a background rate that we will have some confidence in. I certainly don't want to limit the scope, but am not sure how critters which came and went without leaving a record (that we have been able to see so far) can be incorporated into our work otherwise.

 

[Nereid]

Bystander wrote: Species (cross fingers, knock on wood) --- tough as that is in the fossil record.

Would you consider restricting this to just eukaryotes? Even there, how do we address the fact that there are widely differing estimates of the number of species of multi-cellular organisms, in most of the major Classes (think of Insecta)?

Bystander wrote: Long as there is a continuous record before, through, after the event(s) we examine (major extinctions), I'd say look at whatever we can get our hands on, characterize it as sampling some "environment type" during an extinction event, and see if my hypothesis that there ain't no Lakes Malawi, Victoria, Tanganyika, Hawaiian chains, Galapagos, or Andean ridge ecologies showing up in the fossil record holds any water.

If we choose to set these aside, aren't we automatically discounting "widespread loss of 'island' ecologies" as a potential cause of a mass extinction (no matter how such a loss came about)? Otherwise I think it's a very sensible place to start.

 

[russ_watters]

Oy - I have some homework to do...

 

[Ivan Seeking]

Originally posted by russ_watters
Oy - I have some homework to do...

That's what I keep saying.

I feel like a goldfish in a school of Tuna.

 

[Bystander]

Originally posted by Nereid
If we choose to set these aside, aren't we automatically discounting "widespread loss of 'island' ecologies" as a potential cause of a mass extinction (no matter how such a loss came about)? Otherwise I think it's a very sensible place to start.

No "fossil rate" to compare 'em to, at which point, we can assume or assert any number of things: 1) there have been no isolated systems in the past, and the fossil background rate is valid as is; 2) the number of isolated systems in the past has been equivalent to what we see today, and the disappearances of those systems contributed in no way to the background rate (all organisms were integrated into the general/global system); or, 3) an equivalent number of isolated systems that disappeared without trace, and without net contribution to the number of species (comparing initial appearance of system to its disappearance).

Lake Victoria is my overworked case in point --- 400 appearances in 14000 years, and how many species in its previous live lake-dead lake cycles over the past million? Four hundred cichlids gone, but also appeared, for a net zero as far as the scoreboard goes. The isolated environments have got to be contributing a net increase in number of species over the past billion years, but the rate at which they contribute is a little tough to estimate. As far as extinctions of isolated ecologies, when they disappear, they don't take the original populations of the pioneering species with them --- "Victoria dies" does not imply the collapses of Malawi and Tanganyika cichlid populations, nor S. Amer., and points west. Tropical fish hobbyists (including me) ain't happy with the Nile perch, nor the geniuses who introduced it, but in the long run, the lake's a goner, and the Victoria cichlids are goners (barring a wet enough climate to overflow the lake into other drainage basins prior to its drying out again).


quote:
--------------------------------------------------------------------------------
Originally posted by russ_watters
Oy - I have some homework to do...
--------------------------------------------------------------------------------



That's what I keep saying.

I feel like a goldfish in a school of Tuna.

Mackerel, sharks, bluefish --- this is going to be fun if the workload doesn't kill us all.

Edit: Horribly long-winded way of saying that inclusion of currently observed rates of extinctions of isolated species "automatically discounts" contributions of the same effect in the fossil record due to the fact that they are too insignificant to be observed there.

 

[Nereid]

Concrete proposal for step 1

Thanks everyone for the inputs.

Recap: step 1 is "We all agree on what constitutes a mass extinction."

How about:
a) it's rapid; takes place in < 100,000 years
b) it's widespread; extinction is seen in different phyla and divisions, in widely different locations (not islands), and many different habitats
c) a significant fraction of all species (>60%) and families (>10%) go extinct.

For b):
- select 3 from the 'big 9' animal phyla (I've got my favourites; you take your pick; link:
http://ebiomedia.com/gall/awob/ )
- select 3 from the 13 divisions of plants (link:
http://en.wikipedia.org/wiki/Plant)
- if our choices take us to 'insufficient data', we'll reconsider the choices

For locations and habitats, I don't have a proposal - can someone help out?

For c): since we can't count all species (nor families?), we should agree on a robust method for making estimates.

Yes/No/'I've got a better idea'?

 

[Bystander]

Originally posted by Nereid
Recap: step 1 is "We all agree on what constitutes a mass extinction."

How about:
a) it's rapid; takes place in < 100,000 years

Make it an even million --- still going to be tough to get the stratigraphy correlated among locations.

b) it's widespread; extinction is seen in different phyla and divisions, in widely different locations (not islands), and many different habitats

--- or, we can spot it in two or three different locations/stratigraphic units that are/can be correlated, and that are "continuous" records for the period of interest?

c) a significant fraction of all species (>60%) and families (>10%) go extinct.

>30% of species, or we might have to throw out one or two of the "major" extinctions.

For b):
- select 3 from the 'big 9' animal phyla (I've got my favourites; you take your pick; link:
http://ebiomedia.com/gall/awob/ )

Molluscs, annelids, arthropods --- covers terrestrial and marine.

- select 3 from the 13 divisions of plants (link:
http://en.wikipedia.org/wiki/Plant)

Whatever gives us pollen or spores.

- if our choices take us to 'insufficient data', we'll reconsider the choices

For locations and habitats, I don't have a proposal - can someone help out?

Something we can correlate to equivalent current systems --- swamps, salt marsh, estuaries, deltas?

For c): since we can't count all species (nor families?), we should agree on a robust method for making estimates.

Marker species? Ugh --- don't like that at all.

Yes/No/'I've got a better idea'?

Not necessarily "better" --- alternative, but it can wait --- it's not yet obvious to me that it'll yield any insights.

 

[Nereid]

Nereid: For locations and habitats, I don't have a proposal - can someone help out?
Bystander: Something we can correlate to equivalent current systems --- swamps, salt marsh, estuaries, deltas?

Could someone point us to a formal classification system for habitats?

Nereid: select 3 from the 'big 9' animal phyla
Bystander: Molluscs, annelids, arthropods --- covers terrestrial and marine

How about chordates instead of annelides (better fossil record)?

I'm OK with 1 million years (a bit too long, but OK).

My choices of plant divisions: {TBA}

Russ? Are you still with us?

Anyone else have an opinion? want to contribute?

 

[Bystander]

Might as well continue with the agenda? Structured inquiry doesn't seem to be quite as stimulating as a political debate.

p.s.--- "ecosystem classification" doesn't appear to be an "exact" science.

http://modis-atmos.gsfc.nasa.gov/ECOSYSTEM/
http://srmwww.gov.bc.ca/cdc/sei/sunshinecoast/classification.htm
http://www.environment.govt.nz/info/froude/env-class/page29.html
http://www.colby.edu/~ragastal/GE251/Paleoecology.htm
http://biogeo.nos.noaa.gov/products/hawaii_cd/htm/refer.htm

 

[Bystander]

Okay --- time to get this pup moving again --- on to steps 2 & 3:

Originally posted by Nereid
Over on the Politics & World Affairs sub-forum, in a thread called climate risk 'to million species'*, I asserted that the Earth is the midst of the sixth mass extinction**. There was some disagreement, so I suggested that we apply the scientific method, and test the assertion. More discussion, much agreement, ... and here we are.

So, my proposal:
1) We all agree on what constitutes a mass extinction.

30%? 1Ma? Three a year? I can live with that.

2) Bystander and Russ propose a definition of the 'normal' or 'background' extinction rate; we discuss it and agree.

Couple approaches: 1) the number of species currently in existence is equal to the number that have appeared over the past 1-3Ga minus the number which have reached extinction over the same time period; 2) the same premise as in "1)" plus terms accounting for extinction events to remove their contributions to a background rate calculated from "1)."

Starting with approach #1,

N₀ = k_app,ave(1-3Ga) - k_ext,ave(1-3Ga) ,
and using 10M as a round number for the current species count, we get
k_app,ave - k_ext,ave = 0.01 - 0.003 species per year. That is, the average NET rate of change in number of species is equal to the difference in the average appearance and extinction rates. Talk about trivial statements of the trivially obvious --- we get no absolute estimates for these rates without appealing to other estimates of the total number of species that have existed, 100-1000 times the currently existing number, or 1-10G appearances in 1-3 Ga, an average appearance rate of 0.3 - 10 species/a. The average extinction rate is then (0.3 - 10) - (0.01 - 0.003).

Approach #2: same game as 1, and subscripting N with number of Ma prior to present to indicate the number of species just prior to the extinction events, using the dates and estimated extinctions from Thomas,
N₀ = 0.35N₆₅ + (k_app -k_ext)65Ma,
... (the eqtns for Triassic, Permian, and Devonian events are left as an exercise for the reader)
N₃₇₀ = 0.35N₄₄₀ + (k_app-k_ext)70Ma,

and, invoking a suspected 6th Cambrian event with a 50% loss as a guess,

N₄₄₀ = 0.5N₆₀₀ + (k_app - k_ext)160M,

and, finally, N₆₀₀ = 1 + (k_app -k_ext)(400 to 2400Ma) .


This removes extinction losses from the average extinction rate; the suspected Cambrian event's inclusion further reduces the background extinction rate. Working backward through the equations, substituting the last, for N₆₀₀, into that for N₄₄₀, and into ta-da, ta-da, we get

N₀ = 6 x 10^-4 + (130-140 Ma)(k_app - k_ext). The difference between the appearance and background extinction rates has increased from 0.003 - 0.01 to 0.07 - 0.08/a ; still no real insights regarding magnitudes for the gross appearance and extinction rates.

Bottom line to this point: "There is absolutely NO merit to discussing 'extinction rates' without reference to appearance rates." The magnitudes of the differences estimated above for the two rates are two orders of magnitude less than the appearance rate of 10 species/a estimated from very crude numbers, and four to five orders of magnitude less than what can be estimated from Lake Victoria cichlid diversification. Picking out a "net extinction rate" of 3/a greater than a net appearance rate which is conceivably greater than 1000/a is going to be tough, particularly if we consider the natural noise level to be expected in such rates over human timeframes as compared to geological time frames.

3) We agree on what the actual background extinction rate has been, up to 1mya.

Comments?

 

[Ivan Seeking]

Can anyone name one new species to evolve in the last 100 years?

I can name many species that have gone extinct in the same time. In other words, the times scales discussed seem much too large. If we are creating a mass exinction the applicable time scale is in hundreds of years, not thousands or millions.

 

[Bystander]

"Absence of evidence of appearances = evidence of absence of appearances?" Not.

No global inventory, no inventory update on even a millenial basis. What's "new," and what's not is pretty much a matter of "More taste! Less filling!" debate.

 

[Ivan Seeking]

Ugh! Then what was the effect of mass extinctions on the appearance rates in the past? Also, why do appearance rates matter? Don’t these change as a long term result of mass extinctions and total populations; as the competition for food and habitat is reduced, and as more species are present to mutate. Given this, it would seem that the appearance rates should remain fairly constant as a function of the total number of species. Yes? No? Keep in mind I'm just a bio-pedestrian who takes his lead from the experts.

Still, the bottom line - what you're telling me - is that there is no way to know the appearance rates in the short term. But I still have a problem with the time scales. If we can show the loss of many more species than can possibly replaced in the short term, then the mass extinction hypothesis would seem to be well founded. This has always been my take. We know it takes perhaps millions of years for a completely new species to evolve, but we also know that they can be wiped out by humans and other influences in decades. This is what I believe we are seeing…at least this is the logic behind the environmental concerns today.

Then we find that there are likely key species like plankton. This also seems a significant aspect of the argument. We can likely sustain the loss of species of something or other unique to southeastern Colorado, but the loss of the world’s plankton is another issue all together. This of course is a concern related to global warming and the loss of the ocean currents created by the temperature difference between the poles and the equator. In the end, our only real interest is the effect on humans. A well populated world that cannot sustain human life is hardly an acceptable option...at least for me and my kind.

 

[Bystander]

Now you're getting to the questions in my mind: What is an "appearance;" what's the variation about the average appearance rate; what's the rate dependence on total number of species, pops., and available range? How do we go about counting species? Is the "North American Fire Ant" a "new" species? It's got a multiple queen system (hearsay) that isn't characteristic of the parent species. The "New World Killer Bee?"

All I can take to the bank at the moment is that appearances outnumber extinctions by the 10M, or whatever the actual number may be, species currently on the planet.

The "key species" argument brings up visions of the old "climax ecologies" of the 19th century. There may be biologists who will insist that we live in a "balanced" ecology, but the only observable property that exhibits anything close to a "constant" steady-state value might be the total biomass --- hunt that number down for a real guessing game --- it might be nailed down to an order of magnitude, but people are forever finding new biomass under icepacks, in the Sargasso, and elsewhere.

Appearance rate is going to drag in punctuated equilibrium vs. continuous vs. combination evolutionary models, and that could get into another guessing game.

You're not a biologist, I'm not a biologist, and the biologists seem to be avoiding this thread in droves. My only real bottom line with the appearance rate argument is that it's a bit odd that all the extinction alarm hasn't included any discussion of the historical appearances and the cumulative appearance/extinction score.

 

[Ivan Seeking]

I know the definition of a species can be somewhat arbitrary, but I guess the most viable for our purposes is the ability to produce offspring. In this sense I have long considered that Great Danes and Chihuahuas are two different species. In principle I guess they could produce a viable fetus, but due to, um, mechanical limitations, and due to other obvious problems with carrying the fetus full term [Dane the dad], I have been told that most likely this is no longer possible. Considering that all dogs have "evolved" from the wolf in recorded history, I guess that given the proper stressors we can see a mutation of a species into a new species within 4000 years. Technically not so, but in practice I would think that this is true. Just ask the Chihuahua!

Key species...hmmm. Now if you or someone else can shoot holes in this argument – the interdependency of ecosystems - then that would change a lot. This is really the basis for most environmental concerns in this regard. In the case of plankton, I think even oxygen production becomes an issue. I am pretty sure that plankton is thought to produce a large percentage of the world’s oxygen. I know this argument was used to promote deforestation, um, forest management.

 

[Bystander]

The Bali, Java, and Sumatra tigers: first two extinct, third endangered; separate species? or, isolated (by post glacial sea level rise) populations of tigers? Do we back up the extinction counter on this? Or, do we advance the appearance counter --- Australian rabbits, cats, rats, pigs, dromedaries?

This almost suggests that the definition for "appearance" is going to include "isolation" of populations, by whatever mechanism, that is sufficient to prevent interbreeding; whenever a population is split between/among two or more ranges that do not overlap, the number of species equals the number of ranges, genetic identity notwithstanding. Florida orange, Texas orange, California orange. Ugh, sounds like something the lawyers would pull.

 

[Rader]

impacts from asteroids

Maybe this link will help you some to make a good estimate. It shows all the major disasters from impacts of asteroids to volcanic eruptions. Mass extinctions from crater impacts that were very large would result in long periods of no sunlight, the larger the crater the longer it would take for the dust to settle, resulting in vegetation loss immedately in first year.. The time period of impact on species, would probably be much less >100,000 years. There is a very good graph at the bottom of the page of the link, for the 5 mass extinctions and 20 minor extintions.

The Shiva Hypothesis". This describes a 30 million year cycle of mass extinctions over the past 540 million years (see diagram). One hypothesis is that this corresponds the the solar system oscillating through the galactic plane as it orbits the Milky Way. Rampino notes that the last crossing of the galactic plane occurred a few million years ago and it has been suggested that this led to a disturbance of comets in the Oort Cloud, some of which could now be approaching the inner solar system.

http://www4.tpg.com.au/users/tps-seti/crater.html

 

[Evo]

Originally posted by Ivan Seeking
Can anyone name one new species to evolve in the last 100 years?

I can name many species that have gone extinct in the same time. In other words, the times scales discussed seem much too large. If we are creating a mass exinction the applicable time scale is in hundreds of years, not thousands or millions.

Here is an example of a newly evolved species of salmon. http://news.bbc.co.uk/1/hi/sci/tech/979950.stm

 

[Ivan Seeking]

Very interesting.

Until now, it was believed that new species took hundreds or thousands of years to appear...

And, in a separate study, insects were found to alter the way they attracted a mate in just nine generations.

The salmon study took place in Lake Washington, Washington State.

The fish were first placed there in 1937. Since then, they have split into two separate populations which prefer not to breed with each other.

Perhaps the current rate of speciation could be estimated?

Also, I think there is another issue not addressed. The rate of extinction can be related directly to habitat loss. If I understand this, we can extrapolate the loss of habitat due to, for example, deforestation in South America, and make an estimate of extinction rates that is much higher than can be directly measured. For example, if the deforestation rate remains constant for the next 50 years, we can be virtually certain of eliminating X millions of species simultaneously. I don't think this kind of reasoning applies to declared endagered species. Aren't we only considering a defintion that compares the current population of a species to the minimum required breeding population? What about populations that are not technically endangered, but that are being reduced at mass extinction rates.

 

[Rader]

new species

Originally posted by Ivan Seeking
Very interesting.



Perhaps the current rate of speciation could be estimated?

Also, I think there is another issue not addressed. The rate of extinction can be related directly to habitat loss. If I understand this, we can extrapolate the loss of habitat due to, for example, deforestation in South America, and make an estimate of extinction rates that is much higher than can be directly measured. For example, if the deforestation rate remains constant for the next 50 years, we can be virtually certain of eliminating X millions of species simultaneously. I don't think this kind of reasoning applies to declared endagered species. Aren't we only considering a defintion that compares the current population of a species to the minimum required breeding population? What about populations that are not technically endangered, but that are being reduced at mass extinction rates.

This overview lists the rate of taxonomical speciation, in other words, the number of Collembola species that have been described each year, since 1758.
From the year 1758 until now about 31 new species a year have been described. If only the last 100 years are taken into account the speciation rate is about 70 new species each year. This increases up to 93 new species a year for the post second world-war period. Finally, the last 10 years, about 82 new species are defined every year. Note the decline in the speciation rate since 1998...
http://www.geocities.com/CapeCanaveral/Lab/1300/doc/species.htm

New Mexican catfish species.
http://www.philly.com/mld/inquirer/news/4185231.htm

New New York frog species.
http://eces.org/archive/ec/np_articles/static/99586440061244.shtml

New Vietnam deer species.
http://wwfindochina.org/conservation/species/saola.shtml

Majority of life diversity yet to be discovered.
Our catalogue of Earth's diversity seems impressive, boasting some 250,000 described plant species, 750,000 insect species and 280,000 other animals. But incredibly, we have yet to discover most of the Earth's species. Scientists have documented maybe 10 or 20 percent of living things, and new species are discovered all the time.
http://www.enn.com/news/enn-stories/2001/09/09072001/s_44847.asp

 

[Evo]

According to this article, scientists are sighting approximately 13,000 new species per year.

http://www.findarticles.com/cf_0/m1590/9_55/55183060/print.jhtml

Of course, just because a new species is "found", doesn't mean that it hasn't been around for a long time.

Perhaps due to the dramatic increase in recent years in searching for new species, we are aware of more species becoming extinct? But I agree that the decrease in habitat and problems caused by humans have greatly endangered many species to the point of extinction that would otherwise have survived.