While increases of carbon dioxide in the atmosphere have people concerned about the planet's future, the scientists say it will in fact be a lack of the greenhouse gas that will bring the end to life, the Daily Telegraph reported Tuesday.
In less than a billion years, as the sun ages and grows hotter, and greater evaporation and chemical reactions with rainwater take away more and more carbon dioxide, its levels will be too low for photosynthesizing plants to survive, they say.
Herbivorous animals will die out with the loss of plants, and carnivores will die off when they can no longer prey on herbivores -- and life as we know it will cease to exist on Earth.
"The far-future Earth will be very hostile to life by this point," astrobiologist Jack O'Malley-James of the University of St Andrews in Scotland said. "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 only surviving organisms -- hardy microbes known as extremophiles -- would have to cope with extreme high temperatures and intense ultraviolet radiation that would likely kill them off eventually, he said.
O'Malley-James said he based his predictions on a computer simulation of the impact long-term changes to the sun are likely to have on Earth.