All animals and plants will vanish from the Earth within the next billion years, a new study suggests. Ironically, Armageddon is going to arrive as a result of too little, rather than too much, carbon dioxide in the atmosphere.
Currently, experts are trying to find ways to cut levels of the greenhouse gas to prevent global warming running out of control.
But as the Sun ages and grows hotter, greater evaporation and chemical reactions with rainwater will take away more and more carbon dioxide. In less than a billion years, its levels will be too low for photosynthesising plants to survive, say scientists. When that happens, life as we know it on Earth will cease to exist. With the loss of plants, herbivorous animals will also die out, as well as the carnivores that prey on them.
Eventually microbes will be all that remains - and for the majority of them even their days will be numbered. After another billion years, the oceans will have dried out completely leaving only the hardiest bugs.
'The far-future Earth will be very hostile to life by this point,' said astrobiologist Jack O'Malley-James, from the University of St Andrews in Scotland.
'All living things require liquid water, so any remaining life will be restricted to pockets of liquid water, perhaps at cooler, higher altitudes or in caves underground.'
The surviving organisms would also have to cope with extreme high temperatures and intense ultraviolet radiation, he said.
Mr O'Malley-James made his bleak forecast at the National Astronomy Meeting taking place at the University of St Andrews. The predictions are based on a computer simulation of the impact long-term changes to the Sun are likely to have on Earth.
As the Sun ages over the next billion years or so, it is expected to remain stable but to grow steadily brighter. The increasingly intense radiation will cause the Earth to heat up to such an extent that the oceans start to evaporate.
The research may also have implications for the search for extra-terrestrial life, according to Mr O'Malley-James.
'When we think about what to look for in the search for life beyond Earth our thoughts are largely constrained by life as we know it today, which leaves behind tell-tale fingerprints in our atmosphere like oxygen and ozone,' he said. 'Life in the Earth's far-future will be very different to this, which means, to detect life like this on other planets we need to search for a whole new set of clues. We have now simulated a dying biosphere composed of populations of the species that are most likely to survive to determine what types of gases they would release to the atmosphere.
'By the point at which all life disappears from the planet, we're left with a nitrogen/carbon-dioxide atmosphere with methane being the only sign of active life.'