Species extinction? Huge or not so Huge?

Dustin Kesselberg

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I hear alot about species extinction in modern times being comparable to that of the dinosaur times. I'm skeptical of this but would like to know the truth and see the evidence.



How many species have gone extinct in the past 150 years? How many Mammals? Reptiles?


At what rate are species gonig extinct in modern times?


I saw an episode of Penn&Teller about this and they were skeptical of it and saying only a few species have gone extinct and the claims that half of the species in the world will be gone in 100 years is false.

Is this true?


What's the "down low" on this?
 
Tricky. Problem is we don't know how many species there are.
 
There is a school of thought that the numbers are overblown for sensationalism (not how you garner sympathy in the long run, IMHO).

Check out Bill Bryson's A Short History of Nearly Everything, and read the final chapter, entitled "Goodbye". It covers the controversy and what is more likely to be fact.
 
Let's stick with known species.


How fast are "known species" becoming extinct?

At what rate are species dying out?


In 100 years what percent of known species will be extinct? Based on current estimates.


Try as I might I can't find solid scientific answers for these questions, But I know there are answers.


So someone give me some good scientificaly supported answers with some sources to read.



Please!
 
Dustin said:
Let's stick with known species.


How fast are "known species" becoming extinct?
Click to expand...

Again we don't know. So many beetles are known from maybe one specimen.
 
Where is the science behind the claim that "50% of the worlds species will be extinct by the end of this century."?
 
Dustin said:
Where is the science behind the claim that "50% of the worlds species will be extinct by the end of this century."?
Click to expand...

You estimate how many species exist in a certian habitat. You try and figure out how much of that will be left in 100 years and do the maths. Ok it is probably a bit more subtle but that is the basis.
 
geni said:
You estimate how many species exist in a certian habitat. You try and figure out how much of that will be left in 100 years and do the maths. Ok it is probably a bit more subtle but that is the basis.
Click to expand...



You aren't really answering my questions.


Where are the studies?

Post the links.
 
Dustin said:
Post the links.
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Links? What journals do you have subscriptions to?


You are probably looking for things like:

How species diversity responds to different kinds of human-caused habitat destruction
Lin ZS, Liu HY
Source: ECOLOGICAL RESEARCH 21 (1): 100-106 JAN 2006
 
I'm looking for links that I can click that lead me to a site I don't have to pay for. Nothing much asked.

What scientific studies support the claim that 50% of the worlds species will die out by the end of this century? Any? Simple question.





Someone else please post who has knowledge of the area.
 
Dustin said:
I'm looking for links that I can click that lead me to a site I don't have to pay for. Nothing much asked.
Click to expand...

You want studies you don't have to pay for. That generaly doesn't happen.
 
I read last year a metastudy done on the topic, which was interesting. Sorry I can't produce the details of the paper; I had it sent to me by a friend who worked in the field. It was an ecology journal but that's all I can recall, however it was interesting because it involved something I was interested in during my uni days and that's molecular phylogeny.

The short of it was that it's impossible to predict species destruction without knowing a speciation rate. Drawing lines between individual species is misleading and does not give an accurate portrayal of what constitutes an extinction. It's obvious when there are no more African elephants, however the extinction of the striped Madagascan grey beetle in respect to the related spotted Magagascan grey beetle might be a little bit harder to describe.

Additionally, there is no supporting evidence to link biodiversity with the strength of an ecosystem (when measured in terms of productive biomass). If strength is examined in terms of an ecosystem's ability to sustain abiotic changes, the story gets even more vague and uncertain.

The answer; we don't know. Genotype combinations are lost and created every day with changes in organism population. Describing the details is a Herculean task that requires precise definitions, something we are only now working out.

Athon
 
So there isn't science behind the claim that "50% of the worlds species will be extinct by the end of this century."?

Considering I hear it alot from T.V. and News reports about massive species extinction currently occuring.

What are the studies supporting a massive species extinction currently occuring?
 
I don't know where the '50%' statement came from. I'd ask that to be sourced. I've read a range of figures although can't say I've read any papers that give confident estimates. I suspect most percentages touted in the media are extrapolated from local surveys, and therefore are wild estimates.

Biodiversity is one of the most disputed fields in ecology, mostly because good information on the topic is so thin. I could find five different ecologists - all respected in their relevant fields - who could give you five different scenarios.

Biodiversity in selected localities over the planet is decreasing; there's little to argue there. And there is undoubtedly a strong anthropological impact. Our impact on a diverse range of environmental factors is influencing the competition of numerous species; some for better, some for worse. How this pans out in the future is anybody's guess.

Are there large numbers of species disappearing? Define large. Is there an anthropological bias? Yes. However the size and the relevant impact of these changes on the future productivity and health of various ecosystems is still unclear. The rate at which biodiversity changes depends on diverse factors such as migration, mutation rates, population proximity and relatedness... the list goes on.

I think it is important to note that conservation is significant purely because a genetically diverse system offers more options than one without the diversity. And since we aren't certain on the fate of many ecosystems, sustainability is the best option until we have more control over our decisions.

Athon
 
Dustin said:
Someone who can answer my questions please post.
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Go to the library. Check out Bryson's book. That's free, and if it doesn't answer your questions, there's a good bibliography that should.
 
the 50% figure seems to have come from here....

According to a 1998 survey of 400 biologists conducted by New York's American Museum of Natural History, nearly 70 percent of biologists believe that we are currently in the early stages of a human-caused mass extinction, known as the Holocene extinction event. In that survey, the same proportion of respondents agreed with the prediction that up to 20 percent of all living species could become extinct within 30 years (by 2028). Biologist E.O. Wilson estimated [3] in 2002 that if current rates of human destruction of the biosphere continue, one-half of all species of life on earth will be extinct in 100 years.

http://en.wikipedia.org/wiki/Extinction

Extinction is usually a natural phenomenon; it is estimated that more than 99.9% of all species that have ever lived are now extinct. Currently, many environmental groups and governments are concerned with the extinction of species due to human intervention, and are attempting to combat further extinctions. Humans can cause extinction of a species through overharvesting, pollution, destruction of habitat, introduction of new predators and food competitors, and other influences. According to the World Conservation Union (WCU, also known as IUCN), 784 extinctions have been recorded since the year 1500, the arbitrary date selected to define "modern" extinctions, with many more likely to have gone unnoticed. Most of these modern extinctions can be attributed directly or indirectly to human effects

784 doesnt sound like that much to me....(although i'd probably have felt differently if i'd been a dodo....:D )

but as regards to future extinctions i think its a real stab in the dark as to how many creatures/plants will be extinct in 100 years....we're messing up the natural eco-systems in so many ways that it's definitly possible that there will be a crash of the pyramid....a knock on effect where the extinction of one thing brings about the extinction of many more....

but as has been posted already, the time-frame is arbitary, the future planetory conditions conjecture and the number of organisms around now unknown......so it pretty hard to nail anything down :D
 
From what I remember of my grounding in evolution, from a US public school, no less, is that the interplay between the deviations (mutations) of the particular organism and its evironment determine survival. Survival is a prerequisite for reproduction, hence, the fittest survive. The time frame for a gigantic and complex system, like a forest (including trees that live for hundreds of years, fungi that live for a few years, birds and mammals for less, and bugs that live for a couple days) is something beyond our current ability to understand. We can grow cultures of the smallest creatures, we can cultivate trees, even. But I think the thing that bothers people most is that if we just rip-roar through a system, we might not be able to bring anything like it back.

Everybody has a favorite place, some bit of woods or something, that is "different" now, I would guess. Maybe the ocean, a favorite piece of the earth. However, some systems were so inhospitable to man that it was OK to wipe out the mosquito, or to thin out the predators.

It's a question of the primacy of humans. Frankly, humans have demonstrated their primacy already, and will continue. Those of us that care about the broader systems will clean up some messes, to be sure, but we won't have malaria in the meantime.
 
I think one of the methods used to look at species extinction is looking at the sizes of ecosystems.
E. O. Wilson showed that there is a relationship between the size of an ecosystem (in area) and the number of species that it supports. He did this by studying the number species that could be found on islands of varying size. I don't remember the exact formula but it's something like if the area is 1/10 the size, there will be 1/2 as many species.
So, he suggests that, if, for instance, we cut down 90% of the rain forest, we will lose 1/2 of the species it contains. (that's a simplistic example to explain how the idea works).

I don't know how well this all stands up, but it makes plenty of sense to me. Often a species will "go extinct" in a locality, but other members of that species will recolonise later from somewhere else. If there is no "somewhere else", or no way to get from there to here, that local extinction can't be turned around. Of course, there are other reasons why a large habitat might be necessary. For large animals and plants, some of those are obvious.

Again, I don't know if the number 50% can be justified, but I think that methods such as this can probably inform us to some of the dangers of our actions.
 
Dustin said:
So there isn't science behind the claim that "50% of the worlds species will be extinct by the end of this century."?
Click to expand...

Apparently "studies you have to pay to read on-line" aren't real science?
 
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