The Long War

some pretty intricate puzzles to solve.’
    ‘Nobody’s observed this before, have they?’
    ‘Nobody’s had the patience. People always focus on what the trolls can do for them. Not on what the trolls want . Not on what they can do .’
    ‘How come our chimps don’t work that way? I mean, the ones on the Datum.’
    ‘I suspect it’s an evolutionary adaptation to stepping. Out in the Long Earth, where your food source may be near by geographically but a few worlds away stepwise, you need different search and cooperation strategies. The scouts have to spot the food, and return quickly with the news; the group must decide to move in on it rapidly, or not . . . It’s an environment which encourages efficient scouting, precise, detailed communication and quick, robust decision-making. Just as we see here.
    ‘But again, there’s still more to the music of the trolls than the needs of the moment. The long call, the essence of which is spread across the worlds, is a kind of encoded, shared wisdom. The call can last a month before it repeats, and is laden with ultrasonics, beyond human hearing altogether. But even more than that, it’s like a smearing out of consciousness – like nothing humans experience. I’ve been making efforts to decode it. You can imagine the challenge. I’m making some progress; I have a kind of translation suite, in various prototypes.’
    ‘If anybody can achieve that, you can, Lobsang.’
    ‘That’s true,’ Lobsang said complacently. ‘But right now, Joshua, the long call is vibrating with bad news for the trolls. Bad news because of us. Watch this.’ He stood, stiffly, and held up his hands. ‘I am trying to study the trolls in their natural state. I made of this group one basic request, though: that in return for the sanctuary I offer them – protection from humans – they stay here, until I release them. Verbally, I mean, they aren’t physically restrained in any way. Simple as that.’
    ‘And?’
    ‘And now, Joshua, I will release them.’ He clapped his hands, once, twice, sharply.
    The trolls stopped singing – they stopped stepping, once the scouts had returned – and every head, save for the smallest infants’, turned to Lobsang. After a few heartbeats of silence they broke into a new song, a lilting ballad.
    ‘“Galway Bay”,’ Lobsang murmured to Joshua.
    And then they began to step away, mothers with cubs first, males last for protection from predatory elves. In less than a minute they were gone, leaving only a scuffed patch of ground.
    Joshua understood. ‘Gone with the rest, just as the reports say. All over the Long Earth.’
    ‘It’s true, Joshua. And that is what I wanted to speak to you about. Come. Let’s walk. I’m getting stiff from my weeding . . .’
    Across the worlds, June skies remained clear, suns set in unison like synchronized swimmers diving, and dark gathered softly, slowly. On one world an owl hooted, for reasons best known to itself.
    And Lobsang spoke further of the trolls.
    ‘They’ve become vital to the economy of the whole of mankind – including the Datum, if only indirectly. So the corporations, including the Black Corporation, are putting on a lot of pressure, wherever they can apply it, to get the trolls back.’
    ‘And back at work.’
    ‘Yes. Also there are security implications. Worse than the trolls disappearing, if they were to be seen to become an active threat to mankind, if a coordinated military response were provoked – we need to avoid that .
    ‘But there are other, more fundamental issues. The more I study trolls the more convinced I am that they are central to the ecology of the wider Long Earth itself. Like the elephants of the African savannah, they’ve been out there for millions of years, and for all that time they’ve been shaping the landscapes they inhabit – if only by eating so much of them. Sally Linsay taught me this; she’s studied them in the wild, in her way, far longer than I have. If you remove the big beasts from an ecology you can cause something called a trophic cascade. Knocking out the top of a food chain causes destabilization all the way down – booms and crashes of populations – and that can even cause a rise in greenhouse gases, and so on. A tremor of extinctions and eco-collapse all across the Long Earth, or at least as far as the trolls reach. And all because of us.’
    Joshua grunted. ‘Makes you proud.’
    ‘The trouble is, Joshua, there’s no particular