Holocene Sixth Mass Extinction Event In Progress

[SkepticLance]

I can confirm the 2000 lost species in the Pacific, from my other reading. These have been studied in the sub fossil record. The time period was a lot longer than 3000 years, since it includes the islands of Melanesia, which were colonised as far back as 10,000 years ago.

 

However, killing off a lot of species need not take much time. The polynesian Maori of my country arrived 800 years ago, and wiped out 36 species of native bird. Europeans arrived 200 years ago, and wiped out a further 15 species. Most of those the Maori killed were by over-hunting. Most of those by Europeans were by introduction of rats, stoats, possums, cats etc. Although the Maori also introduced the small polynesian rat, which accounted for some smaller bird species.

 

In Australia, evidence is indirect. Te fossil record shows a mass extinction event about 50,000 years ago, in which over 100 species of megafauna died out. Anthropological evidence suggests that humans left Africa about 60,000 years ago, and certainly 10,000 years is ample time to get to Australia and spread across it. The oldest human skeleton in Australia is Mungo Man, about 45,000 years old. Since this was found on the East coast, it suggests arrival of humans on the west coast long before. Some researchers are trying to claim that the mass extinction event was due to climate change. Sadly for that claim :

1. Any climate change at that time was minor

2. There have been much more potent climate changes in Australia over the past 120,000 years without any associated mass extinction.

 

My conclusion is that humans in Australia were the main, if not the only, cause of the mass extinction.

 

The arrival of Clovis Man in North America 'coincides' with another mass extinction of megafauna. The giant Irish elk died out some 10,000 years ago - when humans arrived in Ireland.

 

There is even an interesting theory about Africa (unproven). Apparently, about 1 to 2 million years ago, there were several species of small elephant, which went extinct. Perhaps our pre-human ancestors were at the extinction game also?

 

In terms of mega fauna, there is little doubt that our more primitive forebears killed off a lot more species than modern man has.

[Sayonara]

However, killing off a lot of species need not take much time. The polynesian Maori of my country arrived 800 years ago, and wiped out 36 species of native bird. Europeans arrived 200 years ago, and wiped out a further 15 species. Most of those the Maori killed were by over-hunting. Most of those by Europeans were by introduction of rats, stoats, possums, cats etc. Although the Maori also introduced the small polynesian rat, which accounted for some smaller bird species.

We are fortunate in some respects that this colonisation took place so recently, as it improves the resolution with which we can look back on the ecological changes.

 

Do we know approximately how many native bird species there were at the time?

[SkepticLance]

Sayonara

I am not sure exactly how many there were. Today, there are about 240 native bird species, which would suggest close to 300 before the first humans. This may be a bit misleading, though, since a lot of that 240 are on offshore islands and have limited range. They are NZ birds only because politics gives certain islands to NZ. Certainly, the Maori never visited many of those islands. Taking this into account, I would calculate that the Maori wiped out about 15% of the total they came into contact with, but allow a reasonable error factor in this result. Say 10 to 20%.

[scalbers]

If a few percent of large species have already gone extinct that's significant to me and an ominous harbinger given the rate of increase of the power of humans to alter natural environments. It's alarming to me for example that the largest bird in North America (the condor) came very close to extinction.

 

On the other hand it's more difficult to quantify the number of bacteria and such and how they go extinct.

 

Looking more historically, I wonder why most of the large animals in North America went extinct around 10000 years ago. If this was human caused (as suggested above) this suggests caution with our present activities. The combination of climate change and habitat loss may have a synergistic effect more than either one alone would have.

[JohnB]

Interesting post SL.

 

Although I had always been under the impression the H Sapiens left Africa circa 100,000 years ago.

The arrival of Clovis Man in North America 'coincides' with another mass extinction of megafauna.

Actually, the end of the Clovis culture appears to be linked to a mass extinction. From a recent PNAS abstract;

Stratigraphically and chronologically the extinction appears to have been catastrophic, seemingly too sudden and extensive for either human predation or climate change to have been the primary cause. This sudden Rancholabrean termination at 10,900 ± 50 B.P. appears to have coincided with the sudden climatic switch from Allerød warming to Younger Dryas cooling.

In Australia, evidence is indirect. Te fossil record shows a mass extinction event about 50,000 years ago, in which over 100 species of megafauna died out. Anthropological evidence suggests that humans left Africa about 60,000 years ago, and certainly 10,000 years is ample time to get to Australia and spread across it. The oldest human skeleton in Australia is Mungo Man, about 45,000 years old. Since this was found on the East coast, it suggests arrival of humans on the west coast long before.

Recent dating puts Mungo Man at circa 40,000 years ago. This puts him 10,000 years after the extinction event.

 

Also the Australian record is not as clear cut as you might think. From a 2005 ENS article.;

By systematically analyzing a 10 meter (32 foot) deep section of creek bed, the team uncovered 44 species, ranging from land snails, frogs, lizards and small mammals to giant wombats and kangaroos, including many species previously unknown to have occurred in the Darling Downs fossil record.

 

They knew that the giant marsupials had vanished, but they discovered that smaller species, dependent on a wetter environment, had also disappeared.

 

The results suggest that the extinction of the giant animals whose remains are found at Darling Downs was caused by a massive shift in climate rather than by the arrival of humans who overhunted animals or destroyed habitats by burning the landscape.

The Darling Downs dig failed to unearth evidence of human activity, suggesting Aborigines did not inhabit the region at the same time as the megafauna.

My conclusion is that humans in Australia were the main, if not the only, cause of the mass extinction.

I believe your conclusion is incorrect, or at least not fully supported by the evidence.

[SkepticLance]

To JohnB

Did you consider that human impact in Australia might be more than just over hunting? The aboriginees had a habit of lighting fires. In fact, the early European explorers reported that the entire landscape was a mass of separated smoke columns. This is called 'mosaic burning' and is today hailed as a wonderful positive effect on the ecology. However, it did not happen before humans arrived, and the impact must have been considerable. I could well imagine that the regular burning off of plants would result in sufficient change to, for example, reduce wetland area.

[NowThatWeKnow]

While there may be some argument left on how quickly man is destroying the environment, the fact that he does have a negative impact is obvious to most. Between pollution and consuming natural resources at exponential rates, we will be in trouble at some point. The pictures of air quality at the olympics in China suggest it may be sooner then later.

 

If it is a matter of when and not if, what should we be doing now to correct the problem? While technology is moving quickly, I do not see it staying up with with the population explosion. The population of the world goes up by over 200,000 per day. That is like adding the population of my entire state (Oklahoma) plus another 1 million people to the world every month. How long can that go on? The waste alone from the 90,000 chickens a minute we consume is a problem by itself.

http://www.peterrussell.com/Odds/WorldClock.php

[SkepticLance]

To Now

 

What you said is very much a matter of opinion and there is a more optimistic view.

 

Take pollution. Agreed that China is a heavily polluting nation. However, 100 years ago, so was the USA and Western Europe. London's 'pea soup' fogs as so well described in the Sherlock Holmes stories were a reality. They were caused by rampant air pollution. Ditto water pollution. At that time the Thames River was an open sewer. The eastern cities of the USA were similar.

 

However, in the last 100 years, these regions have cleaned their act miraculously, and fish can now be caught in the Thames, and pea soup fogs are pretty much gone. It is predictable that third world nations will pass through a similar stage and then clean their act up also, as they develop. In 50 years, China will be a much cleaner country.

 

The population explosion. Many authorities believe the population explosion is already over, and we are now dealing with growth that is a matter of inertia rather than excess numbers of children per couple. 50 years ago, the average children per couple in third world nations was 5.5. Today it is 2.5. The reason the world population still grows is simply that the excess children of the previous generation have now reached adulthood and are in the process of having 2.5 children.

 

In the 'advanced' West, the numbers of children per couple is already below 2. In other words, except for recent immigrants from third world nations, and an increase from immigration, Western nations are actually falling in population. Some nations, like Japan and Italy, are so scared of this drop that they are offering financial incentives to women to have babies.

 

The rate of growth is getting less every year, and the United Nations (http://www.un.org/popin) believes it will level out at 9 billion (plus or minus 1.5 billion)by about 2050.

[scalbers]

The trend on population is in the right direction though I'd say it should go further. As standards of living rise and use of resources per person rise, the sustainable population of Earth may end up being less than what it is at present. So once the number levels off I think it should perhaps start to decrease.

[SkepticLance]

scalbers

You will be happy to know that the population trend will be to a reduction after 2050.

 

Population growth is not something we should worry too much about, though we can speed the reduction by making contraceptives more available in third world countries. Hopefully there will be no Dubya to prevent such targeted aid in future.

[scalbers]

Sounds good, though I hope all those people around the world who aspire to have "American" standards of living will be patient enough to wait until after 2050.

[NowThatWeKnow]

 

What you said is very much a matter of opinion and there is a more optimistic view.

 

So you are saying it is business as usual and no change is needed. Jump in the SUV and head to the boat on the lake. This planet can take any thing we can throw at it. The forest getting smaller and the deserts getting larger are no big deal. The scientist saying we are using up our planet faster then it can replenish itself are not only working with a bad time table, they are flat wrong. Hmmm, I am not so sure "optimistic" is the right word.

Edited February 22, 2009 by NowThatWeKnow

[SkepticLance]

Please note that I did not say we could continue with 'business as usual'. The world has environmental problems that need addressing. However, just as stretching the truth into denial of problems is very bad, it is also bad to stretch the truth the other way, and exaggerate problems.

 

Pollution is a problem in China, India and similar places, but it is potentially controllable, and it is predictable (from what we have seen of history) that they will control it in the future. Similarly, population growth is well on the way to proper control.

 

Global warming is still uncontrolled, but the first steps are under way. We need to present a balanced view of the situation, and not go 'all disaster', or else "all is well and we can pollute as much as we like".

[Sayonara]

I concur, SL did not say it was a matter of carrying on business as usual. The point of his post was that other less "environmentally friendly" nations have the same opportunity to clean up their act as nations which have already done so, and that should they make such a contribution then the impact on pollution damage will be of an appreciable size.

[NowThatWeKnow]

Please note that I did not say we could continue with 'business as usual'...

 

No you didn't but your reply to me was in defense of a more optimistic view and did not offer any additional measures that might be considered for a healthy planet. I do not consider myself an environmental alarmist but do see a potential for future problems when it comes to population, pollution and consuming natural resources. I also believe a balance is good but if we do error one way or the other, not giving enough credit to the alarmist could be capable of more damage then following their advise.

[npts2020]

SkepticLance; I would like to point out to you that when Europe and America were becoming industrialized, the populations were a few millions at most and caused enough environmental damage to be noticable. What do you suppose the effects will be if billions of people are permitted to undergo change in the same fashion and at today's rate of resource use? From what I can interpolate from all the writings and data I have seen, we are very near (or even past) the point of no return for melting both polar regions and most (if not all) of the glaciers on Earth. I find it hard to believe that will be a net win for humanity and so far we have "industrialized" only a fraction of the world's population.

[NowThatWeKnow]

...What do you suppose the effects will be if billions of people are permitted to undergo change in the same fashion and at today's rate of resource use? ...

 

At this point, who has the authority to permit or stop another country from developing? We will just sit here and watch the coal go into the furnace.

[SkepticLance]

npts

History is a very good guide to certain things, but predictions based on history have to be modified in the light of modern technology.

 

History tells us that developing industrial countries are dirty and polluting, but later clean up their act. Modern technology for this clean up, though, does not need to be invented again. Thus, we can expect the second cycle of industrialisation, dirty emissions, leading to clean-up, to be quicker. China and India already know they have to clean up, and the technology is there already waiting for them. We can expect them to do this relatively expeditiously. At least compared to the West, which took 100 years.

 

Global warming tipping points are very controversial. I disagree that we are near such 'tipping points'. In the last interglacial period, 120,000 years ago, the average world temperature rose to 2 to 3 Celsius warmer than we now have, and there was no 'tipping point' disaster. The world followed the same pattern it had through all glaciation/interglaciation periods of the current Ice Age. For the world to warm greater than it did 120,000 years ago, will take, at the present rate 160 years or more. This gives us time.

 

There are those who claim that things are accelerating. That is so for CO2 emissions, which are accelerating, but the warming process is not. We know that the relationship between greenhouse gas increase and temperature increase is not linear. An exponential greenhouse gas increase can lead to a linear increase in temperature, and this is what has happened over the past 30 years. Theory says that, unless greenhouse gases increase more than the current exponential increase, warming will remain linear.

 

There is now a move towards methods of running our energy economy, and our agriculture, which will ameliorate greenhouse gas emissions. Given time, this will have its effect, and global warming will slow, eventually stop, and even reverse.

 

There are people who do not agree with this. Some models suggest that anthropogenic greenhouse gases are preventing us descending into the next glaciation period, which is stated to be a good thing. Of course, I am sceptical of models, so regard this as merely one of many possibilities.