How will it all end? Astronomers know the Sun will burn out, and biologists know that the majority of species that once populated the planet are now gone.
|Donald Brownlee, co-author of "Rare Earth," "The Life and Death of Planet Earth", and Professor of Astronomy of the University of Washington in Seattle.
|Peter Ward, co-author of "Rare Earth," "The Life and Death of Planet Earth", and Professor of Geological Sciences at the University of Washington in Seattle|
Paleontologist Peter D. Ward and astronomer Donald Brownlee of the University of Washington, recently published their insights into the future of the planet. The excerpted prologue from their new book "The Life and Death of Planet Earth", poetically portrays a very fragile future – one profoundly grounded by what we now know so far about the distant past.
Indeed in their portrayal, as the Sun inevitably and relentlessly intensifies, survival of species drives a return to the oceans. In effect, a reversal of the evolutionary movie-frames thus begins a dive back into the oceans– just as environmental pressure and resource competition once drove the first leap to land.
Or as the co-authors invite: "Come with us to the future of Earth, a world that echoes our prehistoric past."
Excerpted from The Life and Death of Planet Earth: How the New Science of Astrobiology Charts the Ultimate Fate of Our World
Imagine our planet some tens of thousands of years into the future, a stretch of history far longer than the time it has taken our species to develop from hunter-gatherers to industrial civilization. From the vantage point of a derelict and forgotten satellite orbiting far out in space, the reflection of our marbled home is as disquieting as it is dazzling: a reflective, expanding white.
The ice of the Poles is creeping steadily equatorward as glaciers advance, and the snows of winter are persisting far longer into the increasingly brief summers. The Alps, the Himalayas, and the northern Rockies are capped year-round with growing tongues of ice. Even at Mount Kilimanjaro and the Mountains of the Moon in central Africa, the glaciers are growing. The sea level that briefly rose at the height of civilization is now dropping, exposing new coastal plains, linking islands, and creating land bridges. Harbors have become meadows. The English Channel and the Bering Strait have become corridors. All the maps have changed.
At night the planet no longer glistens with a galaxy of city lights that once stretched from the Arctic to the Southern Ocean. Instead, the Arctic has been abandoned and the Southern Ocean is largely frozen over. The lights that glitter are in a narrower band hugging the equator and midlatitudes. Many are now campfires.
It is as if time has not gone forward, but backward. Eerily, the planet is beginning to resemble again the Ice Age world that our primitive ancestors endured.
The age of fossil fuels is long over, the planet’s reservoir of oil and gas and coal expended in a gluttonous feast of energy consumption that briefly dumped billions of tons of carbon dioxide into the atmosphere. The resulting global warming caused agricultural havoc and erratic climate swings that lasted for several disastrous centuries, but that’s but a blink in planetary time. Slowly, the natural processes that seek to balance our planet reabsorbed the carbon out of the atmosphere. The cruelly hot weather dissipated, and for a while our species rejoiced at a return to "normality." But now the climate has dipped toward a more ominous norm. Earth is returning to the conditions that have dominated it for the last 3 million years: a regime of ice.
|Mars is so cold that carbon dioxide (dry ice) freezes on the winter pole and Venus is so hot that tin and lead would melt on its surface.|
The human civilization that arose in a brief interglacial period is now struggling for survival in a colder and much drier world. The diverse and extensive rain forests of the tropics are being replaced by savanna. The midlatitude grasslands that once helped feed the world, such as the American Great Plains, are becoming dust bowls. Katabatic winds that can reach 200 kilometers per hour howl off the advancing ice sheet and make permanent habitation near its fringe almost impossible. The glaciers are a blue-white wall, gritty on top and at their base, which are grinding forests, towns, and highways into oblivion. Eventually the skyscrapers of Manhattan and the towers of London will be bulldozed by snouts of ice half a kilometer high. Earth has become a planet where humans struggle to feed themselves. Changing climate has made a mockery out of seasons, and the farm crops that predictable seasons allow. Our descendants are starving.
Shiver, and go on.
Come with us to an even grimmer future. The reign of ice will come again, but will not last forever. Fire will succeed it, in the form of an increasingly hot sun.
This time we travel not just thousands of years forward, but hundreds of millions of years: a time more distant from the present era than the ancient seas and primordial swamps that preceded the dinosaurs. The succession of Ice Ages that held the Earth in thrall for millions of years is long forgotten. From space, our planet no longer looks white, or green, or even blue. Its continents are a desolate reddish-brown and its atmosphere thick with windblown dust. Descend in your imagination to an alien world.
Picture that we are standing on a seashore, at the edge of a vast, white-capped ocean. The water, at least, is familiar. As it has been since nearly the dawn of time on Earth, the sea is filled with life. Fleet schools of fish arrow through the sunlit surface waters. Below, on the rippled sand of the sea bottom, persist crabs and anemones, flounders and starfish, corals and barnacles. What is different is that the ocean — once a cradle for the life that crawled onto land — has become a sanctuary. Animals, hammered by a relentless sun, are retreating into the water.
The ocean shore that was once life’s beachhead has become its Dunkirk, and the species that cannot readapt to the water are doomed to extinction. The sandy strand we are standing on has become an oven where a hard cadre of animals struggles to exist between the two worlds of warm water and far warmer air. During high tide a few species of hardy crustaceans and mollusks scurry and hunt, feeding and breeding. But during low tide all visible life comes to a stop, the animals hunkered down under parasol-like shells or wedged within the damp crevices of overhanging rocks, trying to survive the murderous rays of the sun.
Look up. The sky is grayish-yellow, huge winds carrying storms of sand at galelike velocities. The continents have become deserts of scoured rock and marching dunes. Although imperceptible to the eye, the Sun is slightly brighter and the Moon — slowly spiraling away — appears slightly smaller and dimmer. The hottest temperature on record in our own times is the 136 degrees Fahrenheit measured at Le Aziza, Libya, on September 13, 1922. In this future world it reaches that temperature every day, and not just in the Sahara but on midlatitude shores that were once cold and forested.
|This image of the Earth’s atmosphere was taken from Discovery during the STS-96 mission in 1999. Credit: NASA|
The humidity is 90 percent, the air sticky, oxygen thin. We gasp for breath as if on a high mountain.
What life is left? There is no driftwood on this beach, because there are no longer any trees on Earth. Or bushes. Or even grass. The tallest green things left are mosses, found among the more common lichens and fungi that cling to a precarious existence. Even soil is a thing of the past, for when the dying roots of the planet’s flora unclenched their grasp on the topsoil, it flew with the wind, leaving behind rock, dust bowl, and dune. The land has become a vast expanse of sand and rock. The rivers are chocolate Colorados carrying eroded land to sea.
Some animals persist in this new hell. If we get down on our knees we can see that centipedes and spiders still prowl for insect prey. Ants march in search of wrack worth scavenging. Amphibious lizards watch for food. All of these species conduct their business with alacrity, however, scurrying frantically to finish before the punishing sun reaches its awful noon. Then they too must hide.
There are no more birds. Nor mammals, nor amphibians. There is no song and no shade. To try to escape the heat, we too wade into the water, but the surf is uncomfortably hot. We’d have to develop gills and dive deeper to find temperatures that are more comfortable. Yet even the sea will turn out to be only temporary sanctuary for the animals that persist there. The vast oceans themselves are evaporating, their water molecules slowly lost to space. Even they, like all things, will eventually come to an end. The long history of the sea will have left only glistening plains of salt.
Reprinted with permission. Copyright Peter D. Ward and Donald Brownlee. The coauthors also published the acclaimed and bestselling Rare Earth. Don Brownlee is a professor of astronomy at the University of Washington and has been involved in many space experiments; currently he is leading NASA’s Stardust mission to collect samples of a comet and return them to Earth. Peter Ward is a professor of geological science and zoology at the University of Washington and the author of nine other books, including Future Evolution, In Search of Nautilus, The Call of Distant Mammoths, and The End of Evolution, which was a finalist for the Los Angeles Times Book Prize.