The future of the environmental conditions of the planet will depend a lot on human activity. Even excluding the catastrophic hypothesis of a nuclear war (or worse), the environmental damages inflicted by the humans can unstabilize Gaia to the point of threatening the affluence of life that we now observe. The new condition of Gaia would be, almost certainly, less favourable to humans Ė the authors of the unstabilization.
Atmospheric contamination (Ediciones Orbis - Astronomia)
Even disregarding the ominous intervention of the humans, the heating of the Sun will soon make impossible the continuation of the stability that has characterized our planet from the beginning of the Phanerozoic, 540 million years ago. Itís thought that in 100 million years a crisis will arise because the proportion of carbon dioxide that is required for the maintenance of an ideal temperature will be 0%. If no radical solution is found, the Earth will start to heat relentlessly until it becomes uninhabitable. Itís possible that the repeated glaciations that existed during the last few million years are an answer of Gaia to counteract this situation, because the ice is light-coloured and, therefore, it reflects the radiations.
In the distant future, the Earth will end up being so hot that the surface water will evaporate to the atmosphere and a process driving to a runaway greenhouse effect like the one that exists on Venus may become a reality. At the final edge of the Earthís history, the planetary body itself will melt and will be consumed by the Sun during its phase of red giant.
Apocalyptic aspect of Earth in the distant future (Michelangelo Miani)