Megafauna Extinction Due to Climate

jvchamary writes "Most biologists believe that Earth is currently undergoing its sixth mass extinction. The cause? Human activity, either directly (e.g. the Dodo) or indirectly (e.g. the Amazon rainforests). The disappearance 30,000-45,000 years ago of the Australian megafauna, large animals such as the marsupial lion, is often attributed to hunting by Aboriginal settlers. However, recent research in Proceedings of the National Academy of Sciences suggests that it was more likely a shift in climate, rather than hunting, that caused the over-sized organisms to die-out (via Nature and the BBC)."

Comments

WOOT!

[Anonymous Coward]

We Win!

Re:WOOT!

[KiloByte]

What, did you expect that a mere asteroid can be a bigger disaster than us? Hah!

Bummer...

[TripMaster Monkey]

That's too bad...I've always liked the idea of my ancestors storming across the land, exterminating entire species of giant animals with spears and rocks.

Re:Bummer...

[Rei]

Don't give it up so quickly. There are some huge problems with the "climate-only" theory. Namely

A) In most of the world (even if not for some animals in Australia) extinctions were timed, as well as we can measure, with the arrival of humans into each region, even though the global climate was changing as a whole

B) Species survived far more dramatic climate changes in the past, with nowhere even approaching the degree of megafauna losses. The scale of megafauna losses last ice age was staggering - for the largest animals, often over 90% of species.

C) We've seen this occurring in more modern times. For example, the Moa of New Zealand; there is essentially no doubt that they were butchered by the Maori, because their fossilized cooking pits are filled with Moa remains in nice neat layers - huge numbers of them that the species clearly couldn't have sustained. When the Maori were discovered, they talked about hunting and killing them. There's a sudden cutoff point in Maori sites in which suddenly Moas disappear from the diet.

Also, climate change isn't the only alternative theory. There's also the concept of humans being a carrier for diseases/pests, human-induced environmental changes, human killing of "keystone" species, and my favorite, "many of the above combined".

Re:Bummer...

[Rei]

I forgot to mention another reason why climate clearly isn't the only issue: Holdouts. For several species, there were inaccessable regions which humans didn't discover right away - for example, mammoths on Wrangel Island. While the climate changed around them, they survived just fine. Their mainland bretheren, encountering humans and their side effects, died out.

MegaBeaver

[ackthpt]

Interesting bit about the mega mammals. There's a diarama at the Chippewa Nature Center, Midland, Michigan, depicting a giant beaver. Stood about 6 feet tall, probably a few hundred pounds. (what kind of trees did this thing gnaw anyway, it'd need lots of them) Always wondered how they would have died off, I can't imagine too many bow-and-arrow or spear wielding humans able to take on something like that.

Re:MegaBeaver

[Neop2Lemus]

The above, you ignant prudes is not flamebait.

ackthpt, however that is pronounced :-p, I'm not sure the beaver was 6' tall, here's a picture of a model one courtesy of the CBC: Castoroides ohioensis. That's the host of the show, Quirks & Quarks beside him.

mmmm .... marsupial burgers

[Anonymous Coward]

I envy early man and his wider variety of animals to eat

Someone please help me....

[null etc.]

However, recent research in Proceedings of the National Academy of Sciences suggests that it was more likely a shift in climate, rather than hunting, that caused the over-sized organisms to die-out (via Nature and the BBC)."

They died out because they were over-sized! If they were right-sized, they would still be alive! Everyone knows that obesity is the leading cause of anguish and suffering.

Or wait, I'm sorry, they were right. I forgot that climate shifts due to human activity are the cause of all evil.

Part of Nature

[ndansmith]

Human Beings are as natural a part of the Earth's ecosystem as earthworms and aardvarks. We need to accept that our behavior will affect the planet not unlike any other animals.

However, this is not an excuse for an "anything goes" attitude. We still need to work hard to preserve the earth; it is one of our greatest responsibilities.

Solar Activity Coinciding with Climate Change

[bacon55]

There's a lot of evidence to link large scale climate change with periods of heightend and lowered activity in the Sun.

Taken From "http://www.exploratorium.edu/sunspots/"

From 1645 to 1715, there was a drastically reduced number of sunspots. This period of reduced solar activity, which was first noticed by G. Sporer and was later investigated by E.W. Maunder, is now called the Maunder Minimum. This period of time was also unusually cold on earth, and it has been referred to as the "Little Ice Age." This has led to some speculation that sunspot activity may affect the earth's climate. Similar periods of low solar activity seem to have occurred during the Spoerer Minimum (1420-1530), the Wolf Minimum (1280-1340), and the Oort minimum (1010-1050). Solar astronomers label solar cycles from one minimum to the next, and assign them numbers, starting at one, with the 1755-1766 cycle.

Personally, I've always found it rather arrogant to believe we are the greatest cause of climate change on Earth. Lol, it could be that the Sun is literally causing us to use more energy...but thats taking the butterfly effect a little too literally - maybe.

Re:Solar Activity Coinciding with Climate Change

[Rei]

That's not quite accurate. The "little ice age" lasted from 1450 to 1820, a time during which there were sunspot highs and lows. The lows of 1645-1715 (the Maunder minimum) and 1795-1820 (the Dalton minimum) just happened to be the coldest points of it. Some of their other minimum numbers seem a bit odd, too.

The whole "sunspots affecting temperature to the degree we're seeing recently" thing has always been rather suspect. It's not going to affect directly - radiant energy varies by only 0.1-0.2%. But perhaps indirect effects might be occurring, and some have been suggested (such as through altering ozone levels). Nonetheless, the best-predicting climate models currently show that the most important role is played by humans.

A paleoanthropologists view

[Alaska Jack]

Hmm. I know a relatively famous (in his field, at least) paleoanthropologist,and was just talking to him about this very thing. I asked him his thoughts about the two competing theories of large animal extinction.

He said that while it was currently fashionable to blame the climate and exonerate aboriginal hunters, he said it makes perfect sense that it was probably a combination of the two.

We modern humans have a definite tendency to underestimate the intelligence, resourcefulness and persistence of our forebears. A good example of this is all the mysticism and voodoo crackpot theories of how Stonehenge, the pyramids, etc. were built. The fact is that ancient people were quite -- sometimes ingeniously -- resourceful at accomplishing what they wanted to do.

Along that same vein, I have no doubt that they became quite expert at killing such things as mammoths, which would feed a whole clan for months (esp. if you dry some of the meat, etc) and provide ivory, bone and fur besides. Mammoth hunting would also have been a great opportunity for clan members to show their skills, bravery and dedication to the tribe -- something of great importance in many aboriginal societies.

Paleoanthropologists are a pretty interesting bunch to talk to.

- Alaska Jack

Huge liberal bias

[aendeuryu]

When will these "scientists" (who are obviously biased liberals) realize that it's not megaflaura extinction, it's that the megaflaura are experiencing their rapture?

Re:Irrelevant

[AliasMoze]

"...humans will be irrelevant as Transhumans move off-planet..."

This off-planet stuff is confusing. If the population continues exploding, then even within my lifetime there will be a hundred billionish people on Earth. How the heck are we going to get even a million people off the planet, let alone billions of them?

Mass Extinction at the hands of humans eh?

[Thunderstruck]

Well, there are three possible ways to look at this:

1. We're the product of evolution. We're the greatest and most interesting species evolution ever produced. We owe nothing to anyone but ourselves for our success and if we want to wipe out a few other forms of life so be it. We rock! And of course in the grand scheme of things if we did wind up wiping ourselves out, nobody will be around to care.

2. We're the product of intelligent design. If the Christians are right, the whole world is here for us to fill, subdue and use for our benefit. If we need to knock out a few species, its no different than me knocking out a wall in my house to make room for a pool table. We're the pinnacle of creation, We ROCK! And after ragnarok, there will be a whole new creation anyway.

3. We're either created or evolved, but we're adaptable enough that if the need arises we'll find a way to create new species to replace the ones we eliminated. Heck maybe we'll make whole new worlds. In this case, I guess the Mormons would be right. In any case, we're the smartest and most adaptable. We ROCK! In any case, we can always clean up the mess later.

Who am I to suggest I have the right to wipe out whole species? I AM MAN!

It's Bush's fault.

[glrotate]

I'm not quite sure why. I'll have to check democratic underground to find out.

In 10 million years

[Corpus_Callosum]

In 10 million years, perhaps all primary terrestrial life will be descendents of Homo Sapiens. Perhaps we are just in the process of a morphological gene renormalization.

We will have human-derivitive predators, human-derivative herbavores, human-derivitive sea mammals, etc..

Sound strange? It shouldn't. Every once in a while, a specific set of genes shows so much ability to dominate that it completely overwhelm all others and then slowly specializes in the ecosystem, taking on the familiar roles we see. The first Dinosaurs were all morphologically identical with differentiation only occuring as the other species in the ecosystem were driven to extinction and leaving room for the different ecological niches to be filled through evolved Dinosaur morphology. Same with Mammals.

I suppose this vision could require a collapse of civilization such that humans actually had to fill all the various niches in the ecosystem, but given 10 million years, I'd say that is pretty likely. It would be pretty gruesome in the beginning, with canabilism and whatnot being fairly common, but after a few hundred millenia it should shake out to a variety of different predators and prey subspecies quite readily.

Time Enough at Last

[Quantum Jim]

... when you're the last remaining creature, standing on a barren planet (or what's left of it)

Well, at least I still have my books. And the best thing is, there's time now... all the time I need.

<<Picks up a book, but glasses fall off and break.>>

That's not fair! That's not fair at all! (source)

Difference between Humans and Nature.

[H01M35]

I understand the argument that humans are a part of nature, and so are their tools. (By the same token, a bullet to the forehead causes death quite naturally, er, so I'm told.)

The best way I've heard this expressed is Nature doesn't make waste. Nature makes food. (I'd love to claim this, but I can't remember for sure who said it. It might have been Bucky or Amory Lovins. At any rate, all the other species make food, and participate in the food chain and cycle all waste around.

We, as humans create waste that no biological process can deal with. Now humanure can be composted and reused, but there's lots of stuff that is good for no living thing.

That's the big difference. Waste not, want not.

Relevant Dave Barry Quote:

[Fyz]

"What would happen if the Earth was hit by a giant asteroid? Well, judging from realistic simulations invilving a sledgehammer and a common laboratory frog, the result will be pretty bad."