World Engine

by Stephen Baxter

  And it was all, evidently, a conscious human design. He could see that much even from deep space. Where the forest approached the coasts it terminated in straight-line edges. The texture of the forest itself varied from place to place, as if one kind of terrain favoured one kind of tree, another a different species – but these blocks of forest were uniform, and themselves bordered by more straight edges. Huge as it was, this was a managed forest. There seemed to be some human settlement down there, clearings where buildings of white and silver reflected the African sunlight, and there were transport links, silver tracks raised above the tree canopy.

  In places, the forest was burning. Once again the process seemed consciously managed; the brilliant light of the flames occurred in small, straight-edged patches, widely separated.

  ‘Sometimes there is smoke.’

  A voice in his ear that startled him.

  It was Kaliope, the Answerer. She smiled at him. ‘I’m sorry,’ she said. ‘I am programmed to generate noise as I move – footsteps, the rustle of clothing, even breathing – to give you warning. I didn’t mean to sneak up on you.’

  ‘Don’t worry about it,’ he said. ‘When I’m in a study like this I seem to shut out the whole world. Both a strength and a weakness.’ Ruefully he rubbed eyes that suddenly felt tired. ‘When Michael was little, Daddy wasn’t always too good at breaking off from work to go play Buzz Lightyear. “In a minute, kid.” I guess they were usually damn long minutes, for a seven-year-old. Well, I got my payback when none of his descendants wanted to talk to me.’

  She smiled, and headed for a chair beside his. ‘May I?’

  ‘Go ahead.’

  ‘Bartholomew suggested that you’d dug so deep into this vision of Africa by now that a little input from me wouldn’t hurt. Expert input, that is. I’m now connected to the Answerer network at Kufra.’

  ‘Kufra?’

  ‘In southern Libya. An administration centre. We will not land there, but at the space centre at Sabha Oasis, several hundred kilometres to the north-east. Here is Kufra.’ She touched the window.

  A spark lit up in the green, then expanded under magnification into a small city: an airstrip, a road network, white buildings, graceful palms. All this in a neatly delineated clearing in the wider forest.

  ‘Kufra used to be a stop on the caravan routes. Became headquarters of the afforestation project, and is still the management centre.’

  ‘Are those eucalyptus trees? I did some survival training in Australia . . .’

  Kaliope hesitated, as if listening to an unheard voice. ‘Yes. Eucalyptus. Well spotted. And baobabs. Water-retaining, you see. This had been a desert, after all.’

  ‘That city might have seemed futuristic in my day. In the twenty-fifth century it looks a mite old-fashioned.’

  ‘So it is. It was first developed as a headquarters by the World Food Organisation, an arm of the old UN, which strove to use water from the deep African aquifers to grow food for an increasingly starving world.’

  ‘Aquifers?’

  ‘Huge bodies of water that lay undiscovered beneath the sands of the Sahara for centuries, Malenfant. Primarily the Nubian Sandstone aquifer, area two million square kilometres, holding a hundred and fifty thousand cubic kilometres of water.’

  ‘Wow.’

  ‘Relics of kinder epochs. This was not always desert. After the Ice Ages, the north of the continent was naturally green – savannah, woodland – but the paths of the monsoons shifted, taking away the moisture. Now all that’s left of the people who lived here then are rock-art panels with scratched images of vanished aurochs, camels. But the water was there to be retrieved. The Sneddon Centre – that main building – was once the hub of a vast complex of hydroponic food factories.’

  ‘All this before the food printer technology became mature, and nobody had to starve.’

  ‘Indeed. And after that, the land was used for afforestation. And the purpose is capture.’

  ‘Carbon capture! Drawdown from the air. So that’s it. Wow, on such a scale . . . I’m guessing that to cover a desert with forest requires a lot of water.’

  ‘Well, there were two sources, Malenfant. The aquifers, their water pumped up, piped, filtered, recaptured. You can see that some of it was used to create that big inland sea to the south: a reconstruction of a post-glacial lake the palaeontologists called Lake Megachad. Now the largest freshwater sea on the planet.

  ‘And the other source is the oceans. Look here.’ She magnified the area of flooded Tunisia. ‘This is the Roudaire Sea,’ Kaliope said. ‘Created by cutting two-hundred-kilometre canals in from the port of Gabès all the way to the Chott Melrhir, which used to be a salt pan below sea level. And life followed the water: gulls, kingfishers, frigate birds, even dolphins.’ She pointed east. ‘Over there is the Qattara Sea, in what used to be Egypt, fed with Mediterranean water by eighty-kilometre canals. Same idea. There was some local protest at the obliteration of the old landscape. The destruction of ancient caravan routes, for instance. But such had been the extreme desertification of this part of Africa that none of the old Tuareg culture had survived anyhow, the land abandoned.’

  ‘Dolphins in the Sahara. So. What now?’

  ‘Now we land, and you can see the Sahara Forest from close to.’ She grinned. ‘But this is all incidental. There are spaceships down there, Malenfant. Lots and lots of spaceships.’

  He grinned back. ‘You know me so well.’

  37

  The Sabha was evidently a defunct rocket launch site: a few blocky concrete buildings set among desolate stretches of weed- cracked tarmac, and rusting gantries like mute memorials to a forgotten age.

  The Scorpio spaceplane that brought them down from the skyfarm turned out to have VTOL capabilities, vertical take-off and landing. And it was just as well, because here, at the heart of twenty-fifth-century Africa – somewhere in what had been south-west Libya – trees crowded around.

  Once they were on the ground they clambered out of the plane. This might no longer be a desert, but the Sun was high and it felt hot as hell. But Malenfant was immediately distracted by the rocketry stuff: gaunt, ugly relics in the green. One launch ramp looked to him like it had been used to launch OTRAG rockets, a defunct German design. Well, rockets were the reason he had come here.

  However, the trees were the point of the place itself. Not rockets.

  He only had to walk a few metres to get to a perimeter, neat rows of trees pressed up against a wire fence that bordered the aged concrete of the clearing. He heard a hiss, presumably of some irrigation system. He imagined pipes and pumps, reaching down kilometres maybe to those big deep aquifers, feeding trees lined up in military rows.

  He looked back at his party: Bartholomew looking faintly bored, Deirdra staring around wide-eyed. And Kaliope. In the midday sun she cast a short – and entirely artificial – shadow.

  ‘So,’ Malenfant said, pointing. ‘As we saw from orbit. Baobabs and eucalyptus.’

  ‘Well, it’s all about the environment here, Malenfant,’ Kaliope said. ‘These are other water-conserving species. Most of the stock here are actually quiver trees.’ She walked to the boundary, and pointed at specimens of trees that looked odd to Malenfant, primeval, with thick trunks and dense, tough-looking crowns. ‘From southern Africa. The San call them choje. Highly adapted to dry conditions.’

  ‘I don’t understand.’ Deirdra was wearing bright white sun-reflective clothes, a silvered but elegant hat on her head. ‘What’s it all for?’

  ‘Carbon,’ Malenfant said. ‘I looked up some of it before the landing. A tree draws down nearly all its carbon from the air.’ He was tall enough to reach over the fence. He slapped the trunk of a baobab. ‘Look at that. Locked-up carbon dioxide. Just imagine how much of the gassy stuff has been taken out of the air, just to make this one tree. And now all these trees are drawing down all that excess carbon dioxide that my generation left behind, and the even worse lot who followed and burned all the coal. And it’s all en
tirely natural.’

  Kaliope said, ‘The logic is simple, Deirdra. It’s just – well, it’s big. In the end, at Peak Carbon, we had pumped an excess of five thousand gigatonnes of carbon into the air, most of it from fossil deposits. Laid down over hundreds of millions of years, and dug out in a few centuries. Now, the good news is that about half of that will be drawn down naturally into the oceans, in three centuries or so after Peak Carbon. But the other half of the carbon would naturally have to be drawn down by the weathering of the stuff into the rocks of Earth’s surface, which would take many millennia.

  ‘So the goal of the designers of the Sahara Forest was to take care of that second half.

  ‘Now, if you have a square kilometre of forest, and let your trees mature for fifty years or so, you can capture thirty or forty thousand tonnes of carbon dioxide.’ She opened her arms wide and spun around. ‘And if you have the whole Sahara, and you keep that up, you can capture all the excess in three hundred years. Same timescale as the oceans.’

  Somewhat to Malenfant’s surprise, Bartholomew seemed interested. ‘That sounds too simple. You must have to clear your square kilometre, what, every fifty years or so? When the trees are mature, to make room for more to grow. So what do you do with the spare lumber?’

  ‘We burn it,’ Kaliope said promptly. ‘You saw the fires from space, Malenfant.’

  ‘But no smoke?’

  ‘Right. The biomass burns to drive turbines for energy, which is used to collect, liquefy and bury the carbon dioxide released. And then you replant.’

  Bartholomew whistled. ‘So after three hundred years you would have quite a cache of liquid carbon dioxide.’

  ‘True. But that’s a problem for future generations – less bad than the problem that we started with. There are proposals to mine it, actually, as a source for advanced carbon products. Like the stuff they made space elevator threads out of.’

  ‘And irrigation,’ Bartholomew said. ‘What about that?’

  ‘Good question.’

  Malenfant snickered, and whispered to Deirdra, ‘Said one calculating machine to the other.’

  ‘Malenfant. Behave yourself.’

  ‘In fact,’ Kaliope said, ‘all the aquifer water was only sufficient for the first thirty or forty years. But that was enough to kick-start the growth of the forest, and by then, with some subtle geoengineering – and with the changed pattern of climate over the Sahara itself, green stuff rather than desert, and those new inland seas to north and south – the designers were able to divert the monsoon winds to keep the place moist.’

  Malenfant grunted appreciatively. ‘Elegant.’

  Deirdra walked up to the fence, beside Malenfant, peering out. ‘It’s very quiet.’

  Kaliope nodded. ‘The pumps and ducts of the irrigation systems are pretty efficient. Adapted from space technology. You can sometimes hear the hiss of the sprays.’

  ‘But there’s no life. Aside from the trees. No birds calling, no animals.’

  Kaliope said gently, ‘Well, it’s not that kind of forest.’

  Malenfant said, ‘Actually these bits of rocket plant are more my era. I see launch ramps over there, what looks like the wreck of a liquid oxygen store . . . Did they launch OTRAGs?’

  Kaliope nodded. ‘German rockets, tested here in the twentieth century. And then the Soviet Union used it as a test site, briefly. When the coastal spaceports began to flood, at Canaveral, the Guiana space centre at Kourou, there was interest in redeveloping this location. In the end, though, Jiuquan became dominant.’

  Malenfant remembered. ‘The Chinese centre, in the Gobi desert. Trained there once.’

  A handclap, slow, sarcastic, and a familiar voice. ‘Tell me, Malenfant. Is there any important location in your twenty-first-century world that you didn’t visit personally?’

  They turned.

  In the intense sunlight, across a swathe of elderly concrete, Greggson Mica and Prefect Morrel Jonas came walking.

  38

  Deirdra ran to her mother and hugged her. ‘I didn’t know you were here!’

  Morrel said, ‘Well, we don’t all come down to Earth in a noisy spaceplane . . .’

  He looked as if he was sucking a vinegar rag, Malenfant thought. ‘What the hell are you doing here, Morrel?’

  ‘One, I have legal authority over you, Malenfant. And two, it’s my the hell world.’

  ‘“My damn world” would have more idiomatic force.’

  ‘Not helping, Malenfant,’ Bartholomew murmured.

  ‘I have a duty here, Malenfant,’ Morrel snapped. ‘The Planetary AIs forwarded a request that you be equipped to go on an exploratory mission to Phobos.’ He shook his head, angry but rueful. ‘The Common Heritage councils provisionally allow your trip, pending further ratification. Since Homeward, every spaceflight has to be individually approved – you must know that by now. I’m here to tell you so, formally.’

  Malenfant felt like whooping. But he retained his composure. And besides, he had been in NASA long enough to know there could be a world of pain in a phrase like pending further ratification. ‘Thank you.’

  ‘It’s my job.’

  ‘I know.’

  Deirdra did whoop, and she punched the air. ‘And room for me too?’ But she looked apprehensively at her mother.

  Mica glared at Malenfant defiantly. ‘That’s why I’m here. One thing leads to another. I knew something like this would happen. But, Malenfant, taking my daughter off to the Moon is one thing. Mars is quite another.’

  ‘Strictly speaking, Phobos.’

  ‘Don’t get smart with me—’

  Deirdra said quickly, ‘Mother, if we have permission from the councils, and I know we have to get ratification, everything is all right, isn’t it? . . .’ She looked uncharacteristically stubborn. ‘That means you can’t actually stop me.’

  ‘No,’ said Mica tiredly. ‘I can’t stop you. Legally. I won’t ground you, you aren’t a child. I’m here because – I’m just hoping you will think twice.’

  ‘Are you going to offer me Khorgas again?’

  ‘Don’t mock me.’

  ‘No – I don’t mean that.’ She hugged her mother tightly, impulsively. ‘I have to do this. You must see that. I’m on a journey, now, and each step I take . . . It’s what I’m for. That’s how it feels.’

  Kaliope coughed, tactfully, if entirely artificially, Malenfant realised with approval. She said, ‘Maybe it would help to go see the craft you’ll be taking to Phobos.’

  ‘Lead the way,’ Bartholomew said gently.

  Kaliope guided them over the tarmac, to one of the antique-looking buildings, an elderly, crumbled block that had once been a liquid oxygen plant, maybe, Malenfant thought.

  Deirdra and Mica walked together, arms linked. Morrel followed in wary silence. After Malenfant, Bartholomew brought up the rear, lips pursed.

  And Malenfant felt a surge of anticipation. More new toys.

  Inside the building, Kaliope brought them to a modern-looking elevator shaft: modern in that it seemed to be built of what Malenfant was coming to think of as this age’s favourite construction material, the Ubiquitous Ceramic. The elevator had a big car, room for them all, and once they had crowded in, it sank smoothly into the ground.

  Kaliope smiled, as if to ease the tense mood. ‘Some visitors to this place ask if we are descending into one of the emptied-out aquifers. As if they were great empty tanks of rock, rather than strata which had once been soaked with water . . . Actually this is, was, a bunker. This place was a missile base, for a time. When the sea level rise began and the first migrations started, a great deal of wealth was spent by a cabal of local rulers to build a shelter here, in case of nuclear war. A pretty vast shelter, as you’ll see.’

  Malenfant laughed. ‘In your dreams, Doctor Strangelove.’

  ‘But then, when the Homeward movement began, there was a drive to retrieve and protect the monuments of humanity’s centuries of space exploration. We needed an archive. And a saf
e one.’

  The car drew to a smooth halt. The doors opened to reveal a cavernous hall, softly lit. Cavernous – the place was vast, Malenfant saw, with lofty chambers and exhibits of some kind stretching off into a dimly lit distance.

  And Malenfant, thrilled, walked out into what was, for him, a kind of wonderland. The old craft were set up on the floor, some within tall glass cases. Some more delicate or bulky relics were suspended from the ceiling – even some mighty booster stages. All this in soft light, with Answerer screens alongside each exhibit.

  Deirdra walked with him. ‘A lot of memories for you, I guess, Malenfant.’

  ‘I feel I know this place. It’s like the Smithsonian, where my father first took me when I was about five – and, later, I took my own son. The National Air and Space Museum. World-famous aircraft hanging from the ceiling like toy kites.’

  She slipped her hand into his.

  Some of the craft he recognised, some not. A Surveyor, an unmanned lander that must once have sat on the Moon. Over his head, what looked like Mariner 4, a squat box with four faded solar panels, which had achieved the first successful flyby of Mars. If this was the original it must have been retrieved from deep space, from its orbit around the Sun. A shuttle orbiter – it was the Challenger, he saw with a thrill – resting on its undercarriage, ready to go. He wondered if there was a shuttle booster, sister to his own Constitution, down here somewhere.

  Stuff from other nationalities too. A Soviet Soyuz, like a bulbous insect with its two solar-panel wings, hovering over him. A control panel that looked like it had been prised off a steamroller, that turned out to be the relic of a Vostok craft, of the kind Yuri Gagarin had once flown into space. From China, a Long March booster lying on its side, a Shenzhou space capsule, and other deep-space craft he didn’t recognise. Most of the craft were clearly from after his own time, but on this first view he was, understandably he supposed, less drawn to them than to relics of his own memories. He did recognise what looked like an ancestor of the Scorpio spaceplane that had taken him to the skyfarm . . .