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Monday, April 24, 2006 CE

Are we witnessing the Sixth Mass Extinction?


The title sounds alarming and catastrophic. Many people will dismiss it right away and would say that I am exaggerating by insinuating that something like that is actually going on. I cannot say for sure that it is happening, that is why the title of the post has a question mark, however, I am going to present some facts in an objective way.

The world has undergone 5 mass extinctions of species. The first is called the Ordovician-Silurian extinction and occurred around 439 million years ago. 25% of marine families and 60% of marine genera were lost. The second one is called the Late devonian extinction and happened 364 million years ago. 22% of marine families and 57% of marine genera disappeared. The third, and the worst of all, called the Permian-Triassic extinction, occured about 251 million years ago. 95% percent of all specias died out, 53% of marine families, 84% of marine genera and 70% of land species also were gone. The fourth one is called the End Triassic extinction and happened 200 million years ago. 22% of marine families and 52 percent of marine genera disappeared. The fifth one is called the Cretacous-Tertiary extinction and occured 65 million years ago.. It is famous because it included the death of the dinosaurs. 16% of marine families, 47% of marine genera and 18% of lnd vertebrate families became extinct.

Extinction occurs all the time. Species disappear at a rate that oscillates between 1-10 species per year. This is called background extinction rate. Mass extinction occurs when this rate markedly increases causing great number of species to disappear in a short period of time. We have to remember that short period, in a geological scale can mean a couple thousand years.

Mass extinctions occur due to a major disruption in the Earth's ecosystems, either by internal causes, e.g, melting glaciers or volcanic activity; or external causes like asteroid impacts.

Currently, and for some years now, species are disappearing at a rate of 30000 per year. It this rate continues, 50% of all species will have disappeared in 100 years, enough to call it a mass extinction. There is a major disruption of Earth's ecosystems going on, due to global warming and due to the space that humankind is occupying as its population keeps to grow.

The solutions are not easy and will have to include a limitation in the increase of the population and the stopping of global warming. Both processes would take tens to hundreds of years, so in my opinion, there is little that can be done, except to try to minimize the effects of our own activity. There is another pathway. In the event of the collapse of civilization due to lack of fossil fuels or lack of food to feed the billions of people that will be born, war, famine and disease will take care of the human population and would be the means of nature to restore the equilibrium that has been broken.

9 Comments:

Blogger Doctor Marco said...

Q

I forgot you are the eternal optimist. Oil supplies will never end, CO2 does not heat the planet and new species appear from nowhere.

8:41 PM  
Blogger Doctor Marco said...

Q

Burning ethanol still produces CO2. By showing the examples of China, India and Russia you are actually adding a bit of pessimism to your optimist analysis.

10:12 PM  
Blogger Sherril said...

Marco,
I feel like I am interrupting a private conversation between you and Q, but hey, this is America, right? I can interrupt if i want to! I have a question for you, Marco. For a doctor, you seem to be more pessimistic than I would think a healer would be. How do you explain that?

Come to my blog and take the ColorQuiz. I am VERY curious what your results will be.

Sherril

6:22 PM  
Blogger Baconeater said...

One of the creationists main arguments against evolution is that we don't see anything evolve and that all we've seen is species become extinct.

Of course, during an extinction phase in which we are in, species become fewer.

And it is also true that after the mass extinctions are over is when more new species begin to evolve.

6:35 PM  
Blogger Doctor Marco said...

Q:

Jokes aside, even for the overtly optimist, the idea of the collapse of the our way of living creates a chill that is difficult to assimilate. I know that you are a realist that does not want to alarm people for no reason. As I said before, I really wish that we are in th best of the worlds. I do not want to see 30000 species disappearing every year.

12:38 AM  
Blogger Doctor Marco said...

Sherril:

You do not interrupt, you are always welcomed. The first duty of a physician is the compromise with truth. False hope is unethical. I have been trained to be a realist, to give bad news if necessary and always to provide confort.

I will take a look tomorrow to the color quiz, it is getting late.

12:42 AM  
Blogger Doctor Marco said...

BEAJ:

How can a creationist explain that 99.5% of all the species that ever existed on Earth are extinct? According to them, we should be close to the end of the world.

12:45 AM  
Anonymous Anonymous said...

forget my grammar, i´m not kind of good english writer

well, i may believe that wé´re on the 6th wave on extinction, but:
- the mass extinction, its only visible at a high geological time... we are to young in this scale of time, and in the future, there´ll be little evidence of our civilization at stones review (like we do for the past times)
- the organism that tells us about mass extinctions (in their absenses in posterior stratigraphy) only can be preserved as fossil with the correct taphonomy process (including that the fossils represented are the most abundant, and have the structures to be fossilised and be in the correct place at the correct moment)... so, if we not help with extrange stratigraphy, never look o think in an mass exctintion.. maybe, in our era, in our time, a several species will desapear by us, but the larger ones, the dominant ones (remeber, the more commun extinctions now its in species with an endemic distribution, low populations numbers, etc... the great species abundant extinct are contable)... so... in the future, the fossils that maybe be encountered they´re gonna be of species with large populations, and never gonna tell the little species, incluided arthropods, that eleved the rate of actual extinctions

1:23 AM  
Blogger Diane S. said...

I knew it was bad, but I had no idea we were losing 30 thousand species a year. This infuriates me. While cycles of mass extinction have been natural, the blame for this one sets right at the foot of mankind.

How dare we be so irresponsible with our planet.

And to whomever it was that asked, I don't expect China or Russia to reign in their oil consumption for a cleaner globe. Neither have proven to be good global citizens. That does not excuse us from being horrific global citizens, and we are. We are the neighbor everyone on the block hopes will move.

And I agree with you Doc. It is always a scientist first priority to seek out the truth, even when it ain't pretty. But, when faced with possible death, I think it's important to remember to nurture signs of life. The one does not negate the other.

Great post.

8:21 PM  

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