Is there any point trying to save the Earth? Describe arguments for and against environmentalism, and offer your conclusions on the fate of the human race.The Earth has been through some interesting times in its 4.54Ga history. There is evidence that it was covered in ice at various points (though the extent of this ice is somewhat debated still), and that there were times when it was a really crap place to live, such as the Paleocene-Eocene Thermal Maximum. Life on Earth has been through a number of mass extinctions, most notably the Permian-Triassic extinction, resulting in the obliteration of 90% of marine species.
Marine extinction intensity, from Wikipedia
Species have appeared and disappeared. More than 99% of all species that have ever existed on the Earth are extinct. Big deal.
The climate has changed - though we are talking about global warming, we are in a much colder period now than many periods in the past. It has been both warmer and colder than this in the Phanerozoic eon alone. So who's to say that this hasn't all happened before? In fact, the idea of a "resilient Earth" is used frequently as an argument against anthropogenic global warming.
Phanerozoic climate change, from Wikipedia
And yet this is not a comforting state of mind to have. Species go extinct, climate changes, all over geological time scales - that is, over millions of years. Historically, climate has changed sufficiently slowly as to enable species to migrate or facilitate adaptation and evolution. Local changes may be rapid, but global changes are slower (notwithstanding bolides, large-scale volcanism, and so on). What's happening at the moment is faster than we've seen before.
Hockey stick curve, from IPCC 3rd Annual Report
Now, it is possible that we are seeing this rapid change because we are able to see our recent fossil record with greater resolution than the more distant past. However, since the start of the Industrial Revolution, we have burnt millions of years' worth of fossil fuels, chucking tonnes of carbon dioxide back into the atmosphere over and above the normal flux of the carbon cycle. There is a causal mechanism linking atmospheric carbon dioxide levels to global temperatures, via the greenhouse effect. We have lost the golden toad, the Yangtze river dolphin, the Pyrenean ibex, the Western black rhino and the Pinta Island tortoise, just in the past decade or so, and that's just the cute cuddly vertebrates - Flying Spaghetti Monster only knows how many invertebrates and plants have become extinct in that time (though my guess would be hundreds).
As these organisms die out, they clearly affect the ecosystems to which they belong. And of course, Homo sapiens is part of these ecosystems. A soundbite often attributed to Albert Einstein says we'd have about four years left if the honey bees became extinct. It may be hyperbole, but it's rooted in a truth - we depend on the pollination of plants, whether it is by insect or wind. Extinction of many of these species will have a disastrous effect on our survival.
Climate, too, will affect us. We are seeing more droughts, more storms and more extreme weather. As the average annual temperature increases, the arid and semi-arid biomes spread towards the poles. We can grow Mediterranean crops in the southern UK. The boundaries of our major ecosystems are pushing polewards, leaving plants and animals stranded, unable to migrate or colonise quickly enough.
In the end, the Earth probably will recover. The ferns, the cockroaches and the lawyers will survive the next great extinction. The populations of other organisms will bottleneck, and there will be increased diversity millions of years later. But humans are unlikely to make it.
We need to save the Earth and its residents. Without the bacteria, fungi, plants and other animals, we are doomed. The Earth is the only home we have ever known, and if we break it we're not getting another.