If one listens to the currently fashionable hype, the entire planet is doomed simply because some primate creatures are muddling about on and near its surface. The hype can be succinctly summed up with the following statement: “ZOMG! The Earth is Doomed!” But is it really? Sure, if you take a sufficiently long term view. Eventually, the Earth really will be doomed as a result of proton decay if it somehow survives the death of the Sun. But let’s consider things on a smaller time scale than cosmic or even geological time.
First, what does “doom” really mean? At least one dictionary defines “doom” as “fate or destiny, especially adverse fate; unavoidable ill fortune”. Common usage exclusively refers to ill fortune, the cool quote from the council of Elrond notwithstanding. It can also be used as a verb with a like meaning. But how does this apply to a planet?
The obvious definition of planetary doom is the destruction of the planet. This would include such events as the planet exploding or otherwise disintegrating, being split apart by an impact with another object in space, being ripped apart by tidal forces, or falling into a black hole. However, as long as the planet itself exists, it cannot really be said to have attained doom. Any event leading to such devastation is unpredictable or in the far distant future as measured geologically.
Clearly, then, this is not what is meant by those proclaiming the Earth’s imminent doom. Instead, a much more selfish view is implied. This selfishness is not unjustified, however. If the near term fate of the Earth renders it unsuitable for human habitation, then what does it matter to the silly humans currently inhabiting it if the planet itself continues basically unharmed? Perhaps the doomsayers really mean “The Earth as we know it is doomed!” But even that is too generic for all it takes is a major meteorological shift and the Earth as we know it is no more though said shift need not be inimical to our continued existence.
At last, we are zeroing in on the precise meaning of the statement. Let us substitute “Human life” for “The Earth”. Or, for a more friendly statement, use “We”. That means the statement really is, “ZOMG! We are doomed!”. Aha! Now that makes sense.
There are so many possible ways that humans can be doomed. We could be wiped out by a particularly virulent disease. Or perhaps a massive asteroid impact. Or maybe we will manage it ourselves with war. Perhaps we will exceed the carrying capacity of the planet. Or maybe an unfortunate genetic shift will doom us. Perhaps we will poison our own environment? None of these options are particularly far fetched. War is ever present and genocide is not unheard of. Some diseases are nearly perfectly fatal. Sterile or otherwise non-viable mutations occur all the time. Pollution is just a fancy term for poison and famine is a natural outgrowth of exceeding carrying capacity.
So are humans doomed to destruction in the near term? Perhaps. As human actions and natural variation cause changes in Earth’s ecosystem, the carrying capacity of various regions changes, and even the overall carrying capacity of the whole planet changes. As human technological capability changes, so, too, do our needs from the surrounding environment. And we also have the capability to analyze the ongoing changes and take actions to directly affect the ecosystem in both positive and negative ways. Thus, humans as a species will probably survive the apparently looming ecological crisis, but possibly with a vastly reduced population. Massive population collapse would be considered “doom” by those that do not survive, of course, but in general, this might actually be the anti-doom (or salvation if you prefer) of the human species!
Even if humans do not survive such an ecological apocalypse, it is unlikely that life on Earth will cease to exist. Indeed, it is unlikely that humans will manage to damage the entire ecosystem to the point that it cannot recover in some form. I will grant that it is, at least, possible, however. There is a precedent for life surviving such a calamity: consider the bad day that the dinosaurs had some tens of millions of years ago. Had that bad day not occurred, it is unlikely humans would have evolved to be apex predators in the first place (though it is conceivable that we would have, and even conceivable that we could have out-competed the dinosaurs for resources).
So, back to the original question. Is the Earth really doomed? On geological times scales, yes. On time scales that matter to us, probably not. On the other hand, we might be doomed. Through our economic and environmental practices may well cause our own doom. Still, even if we do not straighten out our act, it does not mean we, as a species, are actually doomed, even if we do cause the doom of countless others or even drastically change the ecology of the planet through our actions or lack thereof. So it’s not certain that we are doomed, but it’s also not certain that we are not doomed.
In summary, neither the Earth nor terrestrial life nor humans themselves are facing certain doom, but neither is the future necessarily bright. Doom, prosperity, or mediocrity, none are certain.