Stephen Baxter: Flood

“So what about life?”

He smiled. “Yes, what about it? Listen, I have my own theory about where we’re heading. Don’t quote me. Thandie would kill me if she could hear me.”

“Jeez, I’m not reviewing an academic paper, just tell me.”

“Actually there are precedents. In the days of Pangaea a couple of hundred million years ago, when all the continents were joined into one, you had a semi-global ocean that was an approximation of what we’re facing now. Look, the flood has made a real mess of the biological cycling of carbon…”

Carbon was drawn down from the air into the vegetable matter of plants on land and in the sea by photosynthesis, and then released back into the air through the respiration of living things, and the decay of the dead.

“Before the flood this carbon cycle was dominated by terrestrial life, the green things on land, and we’ve lost that whole major land-based mechanism. And we pretty much lost a second mechanism too, which is the weathering of surface rock-the cee-oh-two is rained out dissolved in water, the acid rain etches the rocks, blah blah. That was only a thousandth the biological component, but on a longer timescale it’s effective-or was.

“What’s worse is that even in the seas the drawdown mechanisms are failing. The rising temperatures are reducing the efficiency of the phytoplankton. The increasing acidity of the oceans isn’t helping either-carbon dioxide plus water makes carbonic acid. Also you don’t get the cold polar currents descending under the warm low-latitude waters, taking oxygen and nutrients to lower layers. That’s why you get algal blooms following storm systems; you get some mixing-up, temporary, localized.”

“We know about that,” Lily said. “We feed off it.”

“We’ve lost all these drawdown mechanisms just at a time when we’ve had a massive one-off injection of carbon dioxide into the air from the fires, and the rotting of the vegetation cover of the drowned land. It’s as if we made a bonfire of everything green on the planet.

“So things have to change. The Earth is a system of flows of matter and energy, of feedback.”

Lily whispered, “Gaia.”

“That’s the idea. The biggest pressure on her has always been a slow heating-up of the sun-the energy the sun pours onto the Earth is up by about a third since life formed. Now, Gaia’s systems adjust, unconsciously, to maintain an even temperature at the surface, a temperature at which life can survive, despite this heating up. In the early days methane was injected into the air, another greenhouse gas, to keep the temperatures up. Some time around two billion years ago the sun’s output was optimal for life on Earth. Since then it’s been getting too hot, Gaia needs to keep cool, and the main way she does this is by drawing down cee-oh-two from the air, and storing it in the rocks, fossil stores like oil, coal.”

Lily nodded. “The less greenhouse gas there is, the less heat is trapped.”

“That’s it. But that mechanism is nearing the limit of its capability. The atmosphere’s cee-oh-two tank is, was, pretty much empty. Gaia was already old, even before the flood, and the hot sun is pushing too hard.

“Some of us think that the glaciation, the Ice Ages, was a kind of experiment with a new stable state. The Ice Ages were tough for humans. But from Gaia’s point of view, if you give up the higher latitudes to ice, you lose a percentage of your productive surface, but you reflect away a hell of a lot of sunlight. Meanwhile life can flourish in the cooled-down mid-latitudes, and indeed on the land surface exposed by the lower sea levels. And the oceans are more fecund when the water is cooler; Gaia likes it cool. So the mechanism worked. But it always looked like a last-gasp effort.

“And now suddenly Gaia is finding herself water-rich, very hot, with very high carbon dioxide levels. She’s under stress again, a kind of stress possibly unprecedented in her history.”

“That’s what Thandie says. Stress-”

“Yes, but we know the Earth likes to settle in stable states, where all its geological, climatic and biological cycles work together. For the last couple of million years it’s flickered between Ice Age and warm interglacial. Now I think Gaia is reaching for a new stasis, a new point of equilibrium, where we’ll see a much higher level of carbon dioxide in the air, and a much higher global temperature. All that heat will generate storms and whip up the sea, promoting life there by stirring up the nutrients, and providing a drawdown mechanism for the carbon dioxide. So you’ll get a stable state, though with a higher cee-oh-two level than before.”

“I see. I think. No need for land at all?”

“No. A whole new stable equilibrium, on a hot, stormy, watery Earth. In a sense you could say this is why the deep subsurface reservoirs have opened up now, to release the water to make this new state possible; the old states, the glacial-interglacial, were on the point of failure. You know what? I did some calculations, just blue-sky stuff. I figure that with a configuration like that there could be more total biomass on the Earth than before. The planet will come out of this actually healthier.”

“But without room for us,” she said.

“Not necessarily. There’ll be plenty of fish in the sea, if we’ve the wit to catch them. But this whole story has never been about us, has it? It’s always been about the Earth, transforming herself as she has in the past. Even if we gave her the kick in the ass that induced her to start the process.”

Lily looked at the children playing in the sea. “Our civilization is gone. Everything we built. But look at those kids swimming. They don’t care that the Smithsonian is drowned, or that we’re all offline forever.”

Gary murmured, “Yes. And even if we pass away, you know, it’s a happy ending of a kind. ‘One generation passeth away, and another generation cometh: but the Earth abideth for ever.’ Ecclesiastes 1:4.” He grinned. “It was Thandie got me looking up the Bible, but don’t tell her that either.”

“So what about you? When North America drowns, will you come with us?”

“I guess not,” he said, as boyishly as if he was refusing nothing more than a second cup of water. “I think I’m done with traveling. And there are people back there I care about.”

Lily smiled. “You always were a people person, in the end. If not for you, Grace couldn’t have survived. But I can’t see you quitting. You’re only fifty-six. I’ll give you some of Nathan’s raft-seaweed to grow.”

“Thanks.” He seemed concerned. “But, Lily, look, the seaweed by itself isn’t enough. Eventually you’ll run out of other stuff. The plastic, nylon fishing lines, everything else.”

“Oh, we know the rafts don’t last forever. Every so often we get hit by a storm we can’t avoid, and a few more are lost. And there are still pirates out there. It’s a steady attrition.”

“And doesn’t that worry you?”

She shrugged. “What can we do about it?”

“It’s a tragedy, you know,” Gary said. “We just ran out of time.” He looked up at the huge sky.“Another fifty years and we’d have had power stations in orbit, and mines on the asteroids and the moon, and we wouldn’t need the damn continents. Well.”

“Yes.”

They stood, helping each other up. Arm in arm, they walked to the edge of the raft, where Gary’s friend was waiting beside their rowboat. He was playing coin tricks for a shoal of children, some of them in the water, some out of it. They looked enchanted.

Gary said to Lily, “I know where you’re heading next.”

“You do, do you?”

“There’s only one place to be, in the end, isn’t there, one last sight to see? You’ve got time, a few years left yet.” He hugged her once more, and clambered down into his boat. They pulled on their oars and the boat slid away. “You just know she’s going to be there.”