"An Earth without People": This month Scientific American takes a look at what would happen to the planet if all or most human beings were suddenly vanish a la Earth Abides or Wittgenstein's Mistress, including a helpful timeline of the disintegration of a city like New York over millennia. Via MetaFilter.

So, say human beings disappeared tomorrow. One of the first things that would happen is that the power would go off. A lot of our power comes out of nuclear or coal-fired plants that have automatic fail-safe switches to make sure that they don’t go out of control if no humans are monitoring their systems. Once the power goes off, the pumps stop working. Once the pumps stop working, the subways start filling with water. Within 48 hours you’re going to have a lot of flooding in New York City. Some of this would be visible on the surface. You might have some sewers overflowing. Those sewers would very quickly become clogged with debris—in the beginning the innumerable plastic bags that are blowing around the city and later, if nobody is trimming the hedges in the parks, you’re going to have leaf litter clogging up the sewers.

But what would be happening underground? Corrosion. Just think of the subway lines below Lexington Avenue. You stand there waiting for the train, and there are all these steel columns that are holding up the roof, which is really the street. These things would start to corrode and, eventually, to collapse. After a while the streets would begin cratering, which could happen within just a couple of decades. And pretty soon, some of the streets would revert to the surface rivers that we used to have in Manhattan before we built all of this stuff.

Many of the buildings in Manhattan are anchored to bedrock. But even if they have steel beam foundations, these structures were not designed to be waterlogged all the time. So eventually buildings would start to topple and fall. And we’re bound to have some more hurricanes hitting the East Coast as climate change gives us more extreme weather. When a building would fall, it would take down a couple of others as it went, creating a clearing. Into those clearings would blow seeds from plants, and those seeds would establish themselves in the cracks in the pavement. They would already be rooting in leaf litter anyhow, but the addition of lime from powdered concrete would create a less acidic environment for various species. A city would start to develop its own little ecosystem. Every spring when the temperature would be hovering on one side or the other of freezing, new cracks would appear. Water would go down into the cracks and freeze. The cracks would widen, and seeds would blow in there. It would happen very quickly.