Peru's southern coast is a slender strip of desert, perhaps 1,800 kilometres long, hemmed in where the Andes meet the Pacific. It is also among the planet's most fragile ecosystems, its web of life easily upset. Rainfall is almost unknown, and whatever water lasts the year round lies far underground, well beneath the surface. That is why the huarango thrives where little else can: its roots outreach those of any tree on the planet. Plunging as deep as 75 metres, they serve the tree but do more besides, drawing water upward into the higher subsoil, where the plants around them can live on it.
How the huarango reshaped the land of the Lower Saran Valley, in southern Peru, is a question Dr Aurel Marchetti, an archaeobotanist at the University of Northmoor, has pursued for years. As he sees it, the tree lay at the heart of what the valley's earliest inhabitants ate, and because its roots could tap water lying far below, it saw those communities through the parched years when everything else they grew withered. Bit by bit, all the same, the huarangos came down and crops took their place. Clear the native woodland and the soil, with nothing left to bind it, simply washes away; let the huarangos vanish and desert is what remains. Today not a thing will grow in the Lower Saran Valley.
The neighbouring Middle Saran Valley leaned on the huarango just as heavily, and for just as long. In its shade people grew their vegetables, and from its seed pods they made food to eat. Herbal remedies were brewed from the leaves and bark; the branches, burned down, gave charcoal for cooking and warmth; and the trunk yielded the timber that raised their houses. That tree is now slipping away at speed. Fuel and farming have already claimed most of the valley's huarango forest, at first only smallholdings but these days sprawling estates that grow produce for buyers overseas.
'Of the forest that covered this ground eight centuries back, no more than four per cent is still standing,' says Emil Sotomayor, a botanist with the Aldergrove Botanic Institute, who, with the ethnobotanist Dr Petra Lindqvist, runs a pioneering scheme to save and rebuild the vanishing habitat. None of it can work unless local people are brought along, and that has meant chipping away at deep-set attitudes. 'These days, the higher a community sets its sights, the more it reads a food tree in your yard or street as a badge of poverty, proof you still grow your own,' he says. Determined not to let the Middle Saran Valley follow the Lower, Sotomayor is coaxing residents into valuing the huarango again, 'reviving a piece of the culture,' as he puts it. He has founded a huarango festival to reawaken local pride and set schoolchildren to planting trees by the thousand.
Sotomayor is convinced that usefulness is the key. 'People will only invest in bringing a habitat back if the tree you offer them earns its keep,' he says. Working alongside local families, he has set about building them a dependable income, converting what the huarango produces into things they can eat. Simmer the beans, he explains, and they reduce to a dark, treacle-thick syrup that can be stirred into a drink or added to a soup or stew. Ground-up pods make a flour for baking, and once the seeds are roasted they turn into a sweet drink, faintly of chocolate, that stands in for coffee. All of it, he notes, is rich in vitamins and minerals.
A few farmers have taken the plunge already. The certified organic farm run by Rodrigo Manrique, the only one of its kind in the Saran Valley and another that owes its start to Sotomayor, has carried huarangos for eleven years. From them he makes syrup and flour, sold at an organic market up in the regional capital. The plot is small and still falls short of supporting him, yet he is sure that will not last. 'Here in Peru the appetite for organic food is growing fast,' he says. 'The future is where I'm putting my money.'
Yet even if Sotomayor manages to rekindle local affection for the huarango, the larger farms remain a danger. Some of them slice straight through the forest, severing the corridors along which mammals, birds and pollen must travel up and down the slender belt of woodland. To counter this, he is persuading landowners to let him plant forest corridors across their property. The added trees, he argues, will help the farms as well, cutting their water consumption by reducing evaporation and offering shelter to the insects that keep pests in check.
'Once we can map the biodiversity and grasp how the pieces connect, we have a foundation to build on. In the desert, a habitat can contract until almost nothing is left,' Sotomayor observes. A rainforest depends on a huge, continuous stretch of land; this place never has. Here life has survived in nothing more than narrow corridors and scattered pockets, and where a handful of trees hang on, numbers climb again rapidly, the species having learned to grab water the instant it comes. He sees the project as a blueprint that might be carried to arid country elsewhere. 'If it works here, in the most fragile system on Earth, that's a real message of hope for many regions, Africa among them, where drought bites hard and waiting for rain is not an option.'
