Marine geophysicist Mike Coffin says humans could wipe out 75% of Earth's species within 500 years

[stuntcat]

http://mobile.abc.net.au/news/2014-01-12/humans-could-wipe-out-75-per-cent-of-all-species-expert/5195984

Humans could wipe out three quarters of the Earth's species within 240 to 500 years in an event known as a mass extinction, a Hobart-based scientist says.

A mass extinction occurs when Earth loses more than 75 per cent of its species in a geologically short time frame.

There have been five mass extinctions - known as the "Big Five" - in the past 540 million years. Those events were caused by asteroid collisions, climate fluctuations and volcanic eruptions.

For the first time, however, a species could be the cause of a mass extinction event.

Professor Mike Coffin, a marine geophysicist from the University of Tasmania, told a conference in Hobart on Saturday that humans are on track to bring about the demise of 75 per cent of the Earth's species within a frighteningly short time period.

What a Pollyanna, most species have less than 200 years.

[bowens43]

1. I bet we could do it a lot faster than that......

[Scootaloo]

2. Here's the funny thing...

We're likely to be among that number, if such DOES happen. Actually we'd likely be one of the earlier casualties, because frankly we are a VERY fragile creature. Adaptable technology can only carry you so far when the food runs out, or all the rain is falling into the oceans, or co2 equals oxygen by volume in every breath you take in.

We're not going to be the post-anthropocene version of lystrosaurus.

[muriel_volestrangler]

3. No, we're highly adaptable omnivores

Look at the range we have - equatorial to Arctic. We can eat mammals, birds, fish, shellfish, grains, roots, nuts, fruit, and some leaves. We can plan, and make conscious decisions to change our eating patterns if we work out that things are going badly. All that is before you consider our advanced technology, such as fire, hunting weapons, and rafts or boats that can cross seas and even oceans to get to better climates.

"co2 equals oxygen by volume in every breath you take in" would be a problem for all air-breathing animals (and would also, I think, imply such ocean acidification that most sizeable water-dwelling animals would die too), but there's no indication it could get that bad. That's more fossil fuel than we can dig out, and more than the earth has ever got to in any of the previous extinction events.

[cprise]

4. You're talking about competition with other species

IMO you can't 'compete' with a whole environment that has shifted to exclude mammals wholesale.

Our toolmaking and planning ability would be overrated in such a case anyway: Not only did we not plan or innovate away from a drastic climate shift, but in basic biological terms a large brain will work even less efficiently in a hotter climate. More than any other factor, however, I fear our immune systems (which aren't special) would not cope with, say, life in an arctic that is simultaneously dark, damp and sweltering for 6 month stretches.

[muriel_volestrangler]

5. The environment won't "shift to exclude mammals wholesale"

We evolved pretty much on the equator, and it gets dark there every night, so " dark, damp and sweltering" is not a problem. Our planning ability is far greater than any other animal - we can say "good food is getting scarce here, we'll try further north/that offshore island/devising a way of hunting new prey".

" in basic biological terms a large brain will work even less efficiently in a hotter climate." - can you explain this, please? Are you saying brains are inefficient in equatorial countries? We'd surely have evidence for that already if it were true.

[cprise]

6. Think about what a 7C increase would mean

though its pretty hard to do. In any case, there is only evidence that we're adaptable within a relatively narrow range. An arctic region that gets hotter doesn't become equatorial; it is something quite different that lies outside of anything we've ever physically adapted to.

Dr. Peter Ward covered the human physiology angle in his book "Under A Green Sky" and wrote about the thermal limits of the human brain. You may want to check that out.