What will "naturally" end land life on Earth (no 1000km comets or hyperatomic wars)?
1 Solar luminosity rise?
2 End of plate tectonics?
3 Slowdown of rotation (unlikely IMHO)?
4 Loss of water or air (ditto)?
5 Something I did not think of?

DHMO will eventually kill us, but don't hold your breath.

... or rather, do hold your breath.

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I think dying will be the thing that kills off land life.

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Probably the only thing that would end land life would be the Sun's increase in luminosity. The end of sea life would happen not long after.

The sun will blow up into a red giant and fry the Earth long before your choices 2, 3, or 4 would happen.

Given enough time, plate tectonics would stop, and then all the land would erode away. No land, no land life. But that takes too long.

Fred

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If something completely destroyed the ozone layer would the excess UV radiation destroy all life on land (or destroy key life such as plants that it would cause the eventual extiction of other land life forms)?

No. Higher animals, probably, but not plants or insects. They are much more resistant to UV light. Even for higher animals the main killer would be blindness; all but the largest ones (man-sized or bigger) breed early enough to produce young before onset of lethal cancers.

For that matter, rodents and other small nocturnal animals which hide during day would be safe even from the blinding effects.

Well, if Peter D. Ward and Don Brownlee are correct in their book, life on land will die due to the lack of carbon dioxide.

Erosion binds CO2 into ground and eventually (in the next 500-1000 million years) CO2 levels will drop so low that plant life becomes impossible. Because there are no more plants to convert CO2 to oxygen, CO2 levels and temperature of the atmosphere will rise rapidly making animal life impossible on the land in the following 100 million years.

Everything dies because we have too much CO2 because we have too few plants because we have too little CO2?
I think there's a major flaw in that reasoning
Has anyone ever told these people about feedback loops?
If lower CO2 levels leads to fewer plants, and fewer plants leads to a rise in CO2, then that rise will lead to more plants.

A better reason why binding CO2 in minerals will kill everything might have been that binding CO2 in minerals removes oxygen from the atmosphere so animal life eventually suffocates.
But that takes a minimal knowledge of chemistry to understand, so it doesn't make for a wide appeal "Let's write about how the world will end and make lots of money" book.
It also won't work until the core has frozen enough to stop plate tectonics from recycling the CO2.

After the plants die, one major CO2 absorber is gone. And plants are important factor in erosion, too.
High CO2 levels and the warming Sun finish the job.

And plants increase erosion and ...

They wrote that there will be some fluctiation, as the amount of vegetation rise and fall.

Trend is that CO2 is disappearing from the atmosphere. CO2 levels are lower than in the Paleozoic or Mesozoic era and much lower than in the Precambrian. Some plants like grass are already adapted to that.

I think they know what they are writing about (altough I think they're too pessimistic). I haven't read their previous book Rare Earth but it has similar views (lots of bacterial life, but higher lifeforms are extremely rare).

I don't think they're that ignorant of chemistry.

I saw some gross (in my point of view) Bad Astronomy in the later part of the book, but I'm not sure if they're to blame (I didn't like the translation at all, it could be the culprit).

According to them plate tectonics will stop after the oceans have evaporated, which won't happen long after the disappearance of land life.

The main point in that book is that advanced life doesn't survive on any planet for billions of years, but is a rather brief event.

If Earth's lifetime was 12 hours, first multicellural lifeforms appeared at 4 am. Bacterial life will be the most complex form of life again at 5 am. Clock is a bit over 4:30 now, so a bit over half of Earth's "happy hour" is already gone.

Ohh dear...we really are not thinking this thing through. First who feels life will remain static for the next billion years? Evolution will continue much as it has today. If higher life is cleaned up by some event, stuff is going to evolve into the vacant niches. Or if the event is extreme enough, evolve into the new niches.

Current land based life does have a fairly grim outlook. As the Sun ages, the deposits of helium ash will cause a steady rise in temperature. Not talking giant phase here, but a steady increase.

What will happen. Life will attempt to adapt, failure will lead to extinction and other more successful animals moving in. The rise of reptiles over amphibians is a classic example of this process.

Success will see creatures we can only guess at. We can assume these creatures will follow the successful body plans already laid down, and fill, within their own evironment the niches animals hold today - Mega fauna etc etc.

So while ever there is material that can be metabolised by an organism...we will have land based life on Earth.

Glen Chapman

Bacterial life will survive easily for a long time, as it has done before, but we multicellular beings are so fragile. Luckily the changes are so slow that life can adapt to the changing environment. But still there are some absolute limits that any known life form cannot cross, like temperature and amount of water.

It is too easy to say life will just survive, it must be backed with facts. I hope somebody can write similar book with a more optimistic -- and well reasoned -- view.

PS. I've got an impression that often astronomers are over-optimistic and paleontologists over-pessimistic when it comes to complex extraterrestial life.

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I think everybody what they have said is right. I like it because form my hometown

I think everybody what they have said is right. I like it because form my hometown

I don't get this at all. CO2 is still going to be released from volcanoes for a lot longer than 100 million years and even if you used a magic spell to remove all the CO2 currently in the atmosphere it would start building up again immediantly from decay enabling many plants to survive. Plants that have access to a constant water supply should be able to get buy on very low levels of CO2. Then there's photosystem I that doesn't require CO2 to generate energy.

Whatever happens, roaches will survive.

And the mute ants.

Only the ones that don't talk?

Dave Mitsky

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Here is a picture of the mute ant looking sad because all his lines got cut.

Edit: That link didn't work. Imagine a sad looking mute ant.

I thought somebody figured out that as the Sun expands its effective gravity lessens so Earth's orbit will relax outwards enough to keep it from being engulfed? Or will the Sun still be Too Darn Close?

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Gimme a minute to read through Jay's latest observations...

No; the effective gravity of the Sun decreases because it loses mass during the red giant phases. During these periods, and the orange sub-giant phases in between, the solar wind increases enough for the Sun to lose significant mass.
http://www-astronomy.mps.ohio-state..../vistas97.html.

Based on the information on that site and elsewhere here is a rough summary of the way I see the future history of Earth's climate;

100-500 years from now; anthropogenic greenhouse effect warms the Earth several degrees, raising sea levels.

1000-1 million years from now; Anthropogenic effects cease (for one reason or another) and Earth reverts to an intermittent ice age.

1 million -100 million years from now; carbon dioxide levels in the atmosphere decrease as carbon is deposited in rocks; this is the overall current trend. Earth becomes a snowball world, intermittently thawed by CO2 buildup from volcanic activity.

100 million years -3 billion years from now; the increasing luminosity of the Sun thaws out the Snowball Earth; but CO2 levels remain low, so plant life must adapt or die. I suspect it will adapt.

3 billion years -5 billion years; the Sun is so luminous that Earth loses all its water and becomes like Venus; life may survive in the upper atmosphere.
(this is based directly on the 'Once and Future Sun' link given above).

5 billion years and on- Earth is first a cinder, then a frozen world orbiting a white dwarf.

Using extreme technology I believe we could maintain a habitable environment on our planet right up to the red giant phase; but after that we would probably have to live on Triton or Sedna, or skip about from world to world as the luminosity goes up and down.

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