Earth Day Doomsday
When people talk about “Saving the planet” they are, in fact, talking about “Saving the human race and a reasonably comfortable way of life.” Even with Human-assisted global warming (Anthropogenic climate change: ACC), acid rain, strip mining, water pollution, toxic waste, nuclear accidents and solid waste proliferation few things that the human race is capable of doing to the planet actually have a great deal of effect in the geological sense.
The Real Ramifications of Global Warming: Waterworld was Wrong?!
Despite the foreboding future of Costner's epically boring film the maximum rise in the Earth's sea levels is about 14 meters. Coastlines would flood, drowning most coastal cities1. The Netherlands and South Florida would be entirely lost to the sea. Large portions of New York and New Jersey would be submerged, and the coastline in the southeast would move miles inland. However, if I showed you an outline map of the world after maximum sea level rise you'd have a hard time telling the difference without direct comparison. Sure, losing these areas would be tragic, but also remember that this amount of change is nearly impossible, as it requires every piece of ice on the planet to melt, and that it would happen gradually. No “Day After Tomorrow” tidal waves wiping out NYC in a single day.
The real danger of ACC is desertification and the drastic shift in the world's climates. The Sahara would grow to dominate half of Africa, the U.S. Great Plains would become a desert, as would much of central Asia. The damage to global food production would be huge and cause civic unrest all over the planet as riots break out and wars to grab resources in areas already plagued with scarcity took place. Even this would eventually balance out, though, as areas that were previously frozen tundra, such as Siberia and Canada, would thaw and become the world's new breadbasket.
So the real danger of ACC is not the damage it would do to the planet, but the damage it would do to our economic and political systems as the distribution of resources changed. The U.S. would be one of the hardest hit, if only because we benefit so favorably from the distribution as it stands today. Russia may actually have the most to gain, as so much of it's land is currently a frozen wasteland, though it would likely have problems with areas that were formerly lightly governed, unproductive provinces realizing they now have the wealth and capacity to go it alone.
Cataclysmic Water pollution: The Sea of Blood
With all the hype surrounding ACC, this much more dangerous and much more permanently damaging phenomenon gets very little press, likely because we understand so little about the balance that constitutes the world's ocean ecosystems. There may be a point in the melting of ice or in the releasing of waste into the oceans, that the entire chemical balance of all of the planets oceans is thrown entirely out of whack, leading to either a massive current change due to salinization levels, or the proliferation of red algae due to rising nutrient (read: human waste) levels. A change in currents would lead to a scenario similar to that of ACC, and would lead to resource wars and world-wide scarcity while adjustments were made to depend on those areas benefiting from such a change.
The result of total algae proliferation (AKA a cataclysmic red tide event) could be a near-complete die out of ocean life, possible the most devastating thing we're capable of doing to the Earth short of an all-out nuclear holocaust. The human population would necessarily shrink drastically due to famine, as 120 million metric tons of food is produced by the ocean each year, and is depended on heavily in the developing world as a major source of protein. This would also take eons for the Earth to correct, effectively hitting a reset button on the development of ocean life.
Neither event, however, will destroy the planet or the human race. Which brings me to the one thing we can do that just might accomplish both.
Nuclear Holocaust: The Candle that Burns Brightest
Here it is, the granddaddy of them all, the Doomsday scenario that was all the rage before ACC came along and stole its thunder: total nuclear annihilation. Keep in mind that I'm not referring to a limited exchange brought on by say, N. Korea or Iran launching a nuke and the major nuclear powers retaliating by turning their country into a glassy plain, I'm talking about a total launch of all payloads currently in operation. While many people believe the event is unlikely to the point of impossibility now that the Cold War is over and science has examined all the ramifications of all out nuclear war (long story short: no one wins), it does stand as the one thing human beings are capable of that could theoretically reduced to Earth to an irradiated ball of dirt.
Oddly enough, the initial conflagration may actually be the least damaging part of the whole sequence. While huge portions of urban population would be vaporized instantly, the vast majority would simply see the mushrooms clouds on the horizon. The real danger to the human race and the planet lies in radiation and dust.
Radiation is capable of some really horrendous things. If you've ever seen pictures of radiation sickness then you know what I mean. But radiations most insidious effect, in terms of the long term survival of the planet, is its ability to damage DNA. It can render both plants and animals infertile, and enough of it could effectively sterilize the planet. It impossible to say if the amount of nuclear radiation we're capable of generating is enough to accomplish this, but its a real enough danger that it stands as the one thing human beings could do to damage the planet so severely that it would virtually have to start over from scratch, with only the lower life forms who's resiliency and simplicity could withstand the damage. Oddly enough, cockroaches are not especially resistant, but fruit flies are.
If the radiation level are not sufficient to render the planet's plant life infertile, then the dust clouds become the most immediate problem. It estimated that a total nuclear war would release 150 Tg (150 X 1012 grams) of dust into the atmosphere, causing global temperatures to fall by 68° Fahrenheit in North America and 86° in Eurasia. This in comparison to the last Ice Age being 44.6° cooler than the planet is today. Precipitation would also drop by 45%. Food production all over the planet would likely cease for at least a year, possibly longer, and most of the world's population would die of starvation. The survival of any of the human race would depend on how long the clouds lasted. Earth, however would outlast the clouds, and the surviving plant life would start the cycle anew.
So what could destroy both the human race and the planet entirely? Asteroid impact? Nope. Comet? Nope. There's only one thing I've found:
Gamma-ray Burst: Not Cool
A GBR is a rare sort of supernova that sends jets of Gamma-rays jetting out of it's poles. If one happened near the Earth it may just strip away a large portion (20-50%) of the Ozone layer, exposing everything to unsafe levels of ultraviolet radiation (our current “holes in the Ozone” are depletions of about 5%). But if one of those Gamma-ray jets is pointed right at us, it could be curtains.
A Gamma-ray jet has approximately the same energy as a hypernova, and would expose the planet to more energy than the sun has in our entire existence. If one happened within, say, 1000 light years and hit us directly it would destroy our atmosphere , the seas would boil, cities would melt and all life would be hopelessly irradiated. Even in the deepest gold mines we would be exposed to lethal amounts of radiation.
You might find all this depressing, but it actually makes me strangely optimistic. These GBRs occur approximately 1/100,000 years in any given galaxy, and the only star we can see that might do it and might be pointed at us and might have a clear shot is between 5k and 8k light years away. A direct hit would likely damage the Ozone and create massive amounts of smog, but would be unlikely to expose us to the massive amounts of radiation that would doom all life on the planet. If this is our only concern for complete annihilation, I feel good about those chances. Plus, if there are any sort of laws to the universe, or sentience determining our fate, going out due to such an absurdly unlikely event just seems unfair and anticlimactic.
So what's my point? People often talk about saving the Earth as if they're doing something altruistic, something entirely selfless that they expect no reward for. This is BS. We are not working to save the Earth for the Earth's sake. The Earth was just fine before we came along, our time here as been geologically insignificant, and it will continue on like we were never here if we manage to kill ourselves off. We are working to save the planet for our sake, and for the sake of our way of life. The rewards may not be immediate, but they are our rewards, not the planet's and not the rest of the planet's life (who would probably be happiest if we would just leave it alone entirely). Forget Saving the Earth, it doesn't need our help, Save the Humans.
What's left to eat? Fish: Net Results
Massive Salinity Changes In Oceans
Wikipedia entries of note:
1Notable U.S. cities lost to maximum sea level rise:
Sacramento (What?! Apparently Sacramento lies in a basin that the San Fransisco bay will spill into. Huh.)