Extinction: Quaternary or Holocene extinction

I think humans have had a large role in the persistence of other species since sharp stones, sticks, and oral communication. Recent technologies are more efficient. Also important is being 7 billion instead of 7 million (or soe other paleo-population estimate).

The super-duper extinctions of the distant past seemed to have acted over a wider range of body sizes. Just could never snuff out the microbes though. Truly, 'too small to fail'.

Most every phylogenetic group seems to include some living fossils; persisting much longer than most others. Mammals present two options there; small rodents and humans. I am going against the wind here to suggest that humans could become the living fossils within Mammalia. Absent human assistance (cities and global ships), where have rats ever been 'all that'?

In science news lately, discussions about how the human microbiome (microbes living in and on us) has been reshaped by antibiotics. This made be think about farmed animals (chickens and larger) routinely fed large antibiotic doses because it speeds their growth. What about those microbiomes? In particular, what about cows? They are famous for microbially converting some of their feed into methane - do antibiotics play a role in that? I am not aware of research.

I am wandering here a bit because I am not really sure what this thread is about. Humans have favored some species and disfavored others. Technology multiplied by population. Seems a broad topic.

 

The Sixth Extinction is well underway, and accelerating. Habitat destruction, deforestation, ocean acidification - all caused by us - are driving many species to the brink. The Dodo's extinct because it tasted good, not because it was lacking in intelligence or adaptability. Climates are changing faster than existing populations are able to adapt.

The sick and twisted irony is that we humans are the one species most equipped to nurture and sustain all of life. We alone can at least try to prevent what caused the fifth extinction, but apparently we have more important things to do. Like make money, which is easily faulted as the root of this evil. Our current economic regime, by regarding the essentials of life as worthless instead of priceless, is an utter failure. As I like to say, life is not an externality.

For more data, Elizabeth Kolbert's The Sixth Extinction: an Unnatural History (reviewed here) looks like an interesting and informative read.

 

If we are to assess the evidence that extinction 6 is going to rank up there with E1 through E5, be prepared for the typically wide range of viewpoints from PCers. For my part, I regard most of the work on calcium-dependent marine organisms as pretty weak. The best of it reduces pH slowly, which has very different outcomes to the slam dunk. Those are an adaptable lot, as they did prove in E1 through E5. They present among the most complete fossil records available, thus they are known.

Only two ways to immortality, lads and lasses. Make bones (or something like them) out of calcium or silica. That puts you firmly in the fossil record and a billion years hence, ye shall be known.

I completely agree with hyo about externalities, and this is pretty much what austingreen said in the other thread. Whatever helps people prosper, focus on that. In no way will such a mono-view prevent E6. But, priorities: we must plan to persist first, and then make sure we do it in a way that preserves 'necessary' biodiversity.

That is also sure to be a controversial subject! It could be that keeping 9 billion humans on earth supported requires the loss of some 'biological furniture'. Expect more disagreements about that!

From my ecological view, not all species are 'equal'. It's all about trophic levels. Primary-producer species are heavily redundant, as are decomposers (with some fascinating exceptions). Herbivores, meh. But when you get up to predators and top predators, than many species appear to have unique ecosystem roles. Discard that furniture at your own risk. Actually humans have done a lot of that since the previous ice age, and continue to. This is what could give E6 a chance at joining the big ones.

I don't argue this to be a complete world view. Many unique pairs of plant/pollinators and seed/dispersers exist, and focusing on trophic levels ignores all that. For critical 'mid-level' species, we could wonder if removing passenger pigeons has increased the need for ag-sprays and GM crops.

But the last is not a testable hypothesis, and Bob already tagged be as the data-loving guy. OK, work with what you got, get data, and look really hard for consonance among (apparently) disparate data. This gets you closer to mechanisms, and actually I am more a mechanism-guy. Data is just that thing you need to go where you want to go.

 

It was in the Tertiary that the mammals triumphed over the dinosaurs.

From what I know about Paleontology and Geologic time, it moves very slowly.

Clearly, it was the rise of the humans that had something to do with the extinction of the mega-fauna mammals, such as the Brontheridium and Megatherium.

Currently, humans are doing it to themselves. I will, however, NOT be around to see the terminal result; as will no human alive today.

 

The 'what' of extinctions is known from biological fossils. The 'why' is coming from stable isotope ratios, and the variety of those being employed is increasing a lot. This is a very interesting era of science.

 

Here's my suggested review paper

Barnosky et al 2011. Has the Earth’s sixth mass extinction already arrived? Nature 471: 51-57.
Doi: 10.1038/nature09678

One message is "Not yet"; another is "We'll get pretty close of the species flagged as endangered now drop off"

A very new one developing a technique to describe which birds may merit the greatest conservation efforts
Global distribution and conservation of evolutionary distinctness in birds. Jetz et al. Current Biology (in press)
Doi: 10.1016/j.cub.2014.03.011

The bad news from Jetz is that many at-risk birds are in Indonesia, a country not known for currently making large efforts to limit the rate of deforestation.

 

To further emphasize monocultures. The chestnut example is one where a wide-ranging species, presumably with a wide range in genetic variation within the species, was quickly taken down by a fungus.

With crops (and also plantation forestry trees that are selected for desired traits). the range of genetic variation within species can become very much lower. So far, I know of no planted species that has been taken down, but there have been close calls, including both corn and wheat.

It gets even more extreme for unusual crop plants like bananas that have been selected to not produce viable seeds. Here, all plants (of a particular variety) are essentially clones. This means they have identical genomes.

In those systems, your productivity can be mighty high until some fungus or insect comes along that can 'unlock the secret'. Then the new organism enters vast areas of plants, all of which are suitable for consumption.

This is a cause for much concern, including establishment of the arctic seed repository. It is also a topic for some gloom&doom in the media, which I shall gloss over. That's just what they do.

However it may be one of those situations where an abundance of caution would cause some to plant more diversity - even if you are strictly in it for the money. But, 'abundance of caution' arguments don't currently have much traction in the agricultural field.