Reforesting the desert

Lima: On a sand dune on the outskirts of Lima, residents of a dirt-poor shanty-town are attempting to grow a forest. This coastline is one of the driest regions on earth – Lima receives less than 1.5 centimetres of rain per year and that, only during a couple of months – nevertheless, the forest plan is not as crazy as it sounds. Before the Spanish arrived here, these Incan hills were wooded, but the trees were cut for timber within a century of European occupation.

Javier Torres Luna, is hoping that reforesting the dunes above his hastily constructed plywood home will provide a long-term solution to an urgent problem: there is no water in his community for drinking, washing or sanitation. And there is certainly none for forestry irrigation. But change is in the air. Literally.

It’s not there’s no water in Lima, it’s just that there’s no rain.

We climb the small hill that rises above Javier’s 10-year-old ‘acentamientos humanos’ community of Bellavista, and it proves difficult to breathe because of the high humidity. A thick, gray fog, known locally as the garúa, hangs perpetually over the city between May and November, hiding the sun and encouraging bronchitis and pneumonia among the city’s poor residents. The fog arises because of a thermal inversion, whereby the chilly Humboldt current cools the water-laden air coming from the ocean, preventing rain along the coast.

Over the past couple of years, Javier and his neighbours have erected a series of large nets at the top of Bellavista hill to harvest precious drops from the wet air. The water is being used for washing, drinking and to irrigate the tree saplings. In as little as four years, the trees will be large enough to trap the fog themselves, producing a self-sustaining run-off that will replenish ancient wells and provide water for the community here for the first time in 500 years.

Lima is a strange location for the country’s capital, the world’s largest desert city after Cairo. Not only is it shrouded in thick fog under leaden skies for more than half of the year – something that the Spanish conquistadors were likely ignorant of during the sunny January of 1535 when they chose the spot for their capital – but because it almost never rains, it is entirely dependent for its water and all of its electricity on the seasonally erratic, drought-prone Rimac river.

The Rimac – currently, a highly polluted trickle – originates in lakes hundreds of kilometres away in the Andes, which are fed by summer rains and glacial meltwater. These lakes are now the focus of tension between the local farmers who depend on their water, and the state-run water company that is emptying them of hundreds of cubic metres per day to send to Lima. Meanwhile, the lakes are shrinking.

More than 70% of the world’s tropical glaciers are in Peru, but global warming is contributing to their fast disappearance. One-quarter of Peru’s glaciers have melted since the 1970s, including two-thirds of the glacier supplying the Rimac. The Rimac’s glacier-contributed volume has declined by 90% in the past 40 years, so that the little – highly contaminated – water that remains is from rainwater.

“The predictions were that almost all our glaciers will have gone by 2030,” says Elizabeth Silvestre, scientific director at the National Meteorological and Hydrological Service (Senamhi) in Lima. “But it’s happening so much faster.”

The problem is worst in the 1800 slum communities of migrants, like Bellavista, which are home to some 2 million people. They arrive in Lima from the countryside, often paying relatively large sums to a ‘land trafficker’ who will find them a plot to squat on. This will be undesirable land, usually on a sand dune and certainly without any water, sanitary system or electricity, somewhere on the outskirts of the city. Migrants construct homes from 3-ply or bamboo sheeting, in time get hooked up to the electricity supply by dealing with privately owned power companies, and eventually can apply for land title. But municipal services, like water, are notoriously slow to come by.

In Bellavista, Javier and his neighbours have given up waiting. With the help of German NGO Alimón, the community has built reservoirs and tanks, and constructed large plant-shade nets using steel cables at strategic points on the top of a hill to trap the precious fog. Fog-carrying wind from the ocean hits the 40m2 nets square on and the results are audible: it sounds like a gushing fountain.

“We had no idea it would work so well,” Javier says. “The only problem is protecting the nets from vandals in neighbouring communities that would destroy our hard work and steal the cables.”

Water courses down the nets where it is captured in gutters and stored in tanks. It falls by gravity through a sand filter where it irrigates the tree saplings and can be used by the community.

After experimenting with various tree types, tara was planted, a native variety that produces an economically important fruit that’s used to produce gallic acid for the tyre, tanning and herbal medicine industry. “Without being irrigated, it would take 400 years for a tara tree to grow to full height in this desert, but with 4-years-worth of watering, it will fruit,” says Luis Marquez Cano, a forestry engineer at the National Agrarian University at Molina, who advised on the project.

In the neighbouring AAHH of Virgen de Chapi B, we find Magally de la Cruz and her 5-year-old daughter living in a small plywood house. She accompanies us up the hill to visit the project that she and her neighbours are pinning their hopes on: Alimón’s “best yet” net, a three-dimensional structure dubbed the Eiffel Tower, which produces as much as 2500 litres of water a day, taking up almost the same amount of space as the regular one.

It’s standing dry when we visit, though. The “wrong kind of fog” is apparently to blame. Whereas it was impossible to see more than 2 metres ahead on the hill above Bellavista, here, a little lower, the air is relatively clear, and what fog there is is ‘dry fog’ – the droplets are simply too small to coalesce on the nets. It means that Magally has no water.

This being election time, though, a noisy and highly visible group of municipal workers has arrived to begin piped water works here. Great news, Magally, I say. You’ll finally have water.

She is more sceptical. “Voting is in a couple of weeks, and who knows if the workers will disappear after the election. It is often that way with projects here,” she says, pointing out the half-finished road.

Even if she does eventually get piped water, it will likely be rationed and there won’t be enough for agriculture. The fog nets, which worked so very well last year, remain important, although how they will fare in the increasingly strong El Niños is every climate scientist’s guess.

So does fog harvesting offer a way out of Lima’s water crisis? The technique is incredibly useful for small communities, up to say 500-1000 people, says FogQuest’s Bob Shemenauer, who pioneered the technique in Chile’s Atacama desert. “For small rural villages and isolated communities, it can be a lifeline,” he says. “But, once a community gets large enough to support businesses, such as cafes, swimming pools, and so on, the per capita water use goes up from 40-50 litres per person, to hundreds. Then, governments need to invest in piped water supply.”

Ultimately, dry places like Lima are simply not suitable for so many inhabitants. Now that the free water storage glaciers are going and gone, governments need to strategise for the changed planet: they need to move cities to where resources are available to provide for them. In Peru’s case, it means moving Lima from the western desert to the wetter east.