Modern civilization has extremely deleterious consequences in regards to species richness, primarily through destruction of habitat. Because of these negative aspects of modernity hunter-gatherers have been idealized as a model of humanity at equilibrium with their ecology. 1491: New Revelations of the Americas Before Columbus lays out the revisionist, and to some extent now mainstream, argument that the American wilderness which European settlers encountered was actually an instance of "re-wilding" in the wake of native demographic collapse due to disease. But setting this case aside, what about Australia? Its fauna was even more exotic to Eurasian sensibilities, and the Australian Aboriginals do not seem to have ever shifted away from obligate hunter-gatherer lifestyles. Perhaps they truly were at equilibrium with their environment, judging from the fact that Australia has so many endemic species.
I think the argument that Australian Aboriginals were at some equilibrium is correct; but only because the havoc that they wrought upon the native ecosystem was relatively deep in the past. The particular destructiveness of modern civilization is a function of its progressiveness and the constant roil of its development. Pre-modern societies characterized by Malthusian conditions whereby population growth was "checked" by natural limitations were static enough over the long term that after an initial transient period of ecological instability a new equilibrium had time to settle in. If humanity is an environmental condition, Malthusian humanity is like a storm which passes. Post-Malthusian humanity is like a perpetual hurricane.
A new paper in Science speaks to the specific case of Australia. And Then There Were None?:
Giant marsupials, reptiles, and flightless birds once inhabited Australia (see the first figure). But 23 of the 24 genera of these megafauna disappeared in the late Pleistocene (125 to 12 thousand years ago). Most Australian megafauna appear to have survived until 51 to 40 thousand years ago, with human impact by hunting or vegetation change proposed as the extinction drivers...Yet, one site has stood out as an anomaly: Cuddie Springs in interior New South Wales. Persistent claims have been made that this site contains megafauna fossils associated with stone tools in sediments deposited 40 to 30 thousand years ago...thus indicating prolonged overlap between people and megafauna. These claims have been challenged...based on concerns about possible reworking of fossils from older deposits. To resolve this conundrum, Grün et al...have now directly dated the fossils themselves. The results provide no evidence for the late survival of megafauna at the site.
Here's the original paper on the Cuddie River site, ESR and U-series analyses of faunal material from Cuddie Springs, NSW, Australia: implications for the timing of the extinction of the Australian megafauna:
The timing and cause of late Pleistocene faunal extinctions in Australia are subjects of a debate that has become polarised by two vigorously defended views. One contends that the late Pleistocene extinction was a short event caused by humans colonising the Australian continent, whereas the other promotes a gradual demise of the fauna, over a period of at least 10-20 ka, due to a combination of climatic changes and ecological pressures by humans. Cuddie Springs is central to this debate as it is the only site known in continental Australia where archaeological and megafauna remains co-occur.
We have analysed more than 60 bones and teeth from the site by laser ablation ICP-MS to determine U, and Th concentrations and distributions, and those with sufficiently high U concentrations were analysed for U-series isotopes. Twenty-nine teeth were analysed by ESR. These new results, as well as previously published geochronological data, contradict the hypothesis that the clastic sediments of Stratigraphic Unit 6 (SU6) are in primary context with the faunal, archaeological and other materials found in SU6, and that all have ages consistent with the optically stimulated luminescence (OSL) estimates of 30-36 ka. These young OSL results were used to argue for a relatively recent age of the extinct fauna. Our results imply that SU6 is either significantly older than the OSL results, or that a large fraction of the faunal material and the charcoal found in SU6 was derived from older, lateral deposits.
Our U and Th laser ablation ICPMS results as well as the REE profiles reported by Trueman et al. [2008. Comparing rates of recystallisation and the potential for preservation of biomolecules from the distribution of trace elements in fossil bones. C.R. Palevol. General Paleontology (Taphonomy and Fossilization) 7, 145-158] contradict the interpretation of previously reported rare earth element compositions of bones, and the argument based thereon for the primary context of faunal material and clastic sediments in SU6 layers.
ScienceDaily has more. Truly veni, vidi, vici is the story of man. The difference with modern man is that the exponent for the last two comes from 1 to ∞. We arrive. And see & conquer. We see & conquer. We see & conquer....
Citation:
ESR and U-series analyses of faunal material from Cuddie Springs, NSW, Australia: implications for the timing of the extinction of the Australian megafauna, doi:10.1016/j.quascirev.2009.11.004
And Then There Were None?, Science 327 (5964), 420. [DOI: 10.1126/science.1185517]
Note: The arrival of the dingo in the past 10,000 years to Australia resulted in a second wave of extinctions, the "Tasmanian Tiger" was extant on mainland Australia until about 2,000 years ago. Tasmania was separated from the Australian mainland before the arrival of the dingo, ergo, the persistence of large carnivorous marsupials down to modern period.
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Actually what is surprising is that so many marsupials have survived and are still thriving in Australia. The last time marsupials found themselves in sudden competition with placentals (the great American interchange - junction of North and South America), the results were pretty dire for the pouchies.
Noble savage; only in Rousseaus' dream time.
Regarding species loss due to habitat destruction, you might wish to read this,
http://wattsupwiththat.com/2010/01/04/where-are-the-corpses/
in which species' losses due to habitat are disputed. The writer finds that very few species have gone extinct due to habitat loss. Wilson's estimate of 40,000 per year was pulled out his but with no evidence, and he has never retracted the wild guess.
I have wondered if aboriginal use of fire may have altered the Australian landscape enough to cause some extinctions.
@Jim, that is one theory for which there is a fair bit of evidence, that systematic firestick hunting caused permanent vegetation change, which might also have induced climate change, making the continent drier. Of course there were always wild fires, but there is evidence in charcoal deposits of much more frequent and widespread burning after the arrival of humans. People very quickly spread to all parts of Australia after arrival, so it happened everywhere, and it is still a traditional practice.
@toto, aside from the arrival of modern humans and then the introduction of the dingo, there wasn't any other arrival of placentals to compete with or be predators on the marsupials until the arrival of European settlers, who introduced rabbits, foxes, and a lot of domestic animals like cats, dogs, pigs, goats, horses, donkeys, camels and even water buffalo which have all subsequently gone feral. Foxes and feral cats alone (plus habitat loss) have already caused the extinction of quite a few smaller marsupials, although their arrival was a really very recent event, less than 250 years ago. So it's still a work in progress, with insufficient time to achieve a new equilibrium. The populations of some species of kangaroo have increased a lot with the introduction of wheat farming - lots more available food. There really hasn't been a comparable event to what happened in South America, but maybe given enough time there could be. Feral camel populations are already getting disastrously high in some arid inland areas, for example.
In North America the animals are adapting and coming back big. I live near Chicago and we have cougars and wolves moving back in. Deer of course are overabundant which may be why the big predators are moving in.
40 years ago it was very rare to see even a white tail deer in this area. If you saw a hawk or a deer you mentioned it to people. I didn't see an eagle until I was teen, now they nest not miles from where I grew up.
I believe the animals are adapting to human presence.
@Tom, One relatively recent change is the proportion of hunters. 100 years ago lots of people hunted not so much for sport as for a way to get needed food. Fewer people hunt for sport or for food today, and a lot less area is available for hunting due to human density increases (although still of a character to support a local deer population). And hunting seasons are more wisely regulated to prevent over harvesting. The increase in deer population and the resurgence of predators is probably more parsimoniously accounted for by those factors, rather than any sort of adaptation on the part of the animals.
Divalent,
It doesn't have to be one OR the other, does it?
The increase in game brings in those predators that are "willing" to hunt near humans, perhaps. While it used to be that any time humans saw a cougar or wolf, the whole town went out to kill the killer, thereby limiting the population of predators to those who "learned" to stay away from humans, now that humans are less likely to hunt every predator that appears nearby, the predators have "learned" that it's safe to come in closer to humans.
@ Bob
Someone is wrong on the internet.
There were a couple of really bad winters in the 1920's which wiped out the Illinois deer herd. Stocking of deer took place, and deer are presently abundant in Illinois.
A 1920 Chamber of Commerce flier on Menard Co., TX, states there are no deer in Menard Co. Today, income from deer hunting leases, and deer hunting activity, is a major component of the County economy. What happened? First, the screw worm fly, the major predator on deer in the area, was eradicated. Secondly, during the drought of '50's ranchers began to feed stock out in the pasture on a year round basis. Deer liked this. Thirdly, ranchers recognized the value of having hunt-able deer. Most land in Texas is privately owned, so most hunting is done on leased land. You can get more for a hunting lease than you can for a grazing lease. There is an industry of breeding trophy bucks,etc.
Divalent
You are certainly right that changes in human activities are a big reason for the return of many species.
There were no goldfinch here until the late seventies. Now they are common. I don't know what specific factor changed.
One thing that is changing big is the great increase in houses being built. This automatically adds to wildlife habitat, but not in any way that mimics any former habitat. Humans like trees, all sorts of trees whether native or not. We plant trees around our homes in areas that were once prairie, and more recently cropland. A brand new habitat that never existed before, with all kinds of new species. The local animal species don't seem to mind.