Dealing with drought: how fog collectors are providing trees with water in Spain

Scientists in the Canary Islands and Portugal are collecting water from fog to enable reforestation of degraded landscapes

As summer fires continue to devastate huge areas of woodland in Spain, France and Portugal, and drought plagues Europe and the UK leaving tens of thousands of acres at risk of desertification, some scientists are busy collecting fog.

The EU-backed Life Nieblas project (niebla is Spanish for fog) is using fog collectors in Gran Canaria in Spain’s Canary Islands, and Portugal, to improve degraded landscape and fuel reforestation.

Fog collectors – sheets of plastic mesh erected in the path of the wind – already exist but have never been used efficiently, says Vicenç Carabassa, the project’s head scientist, who works for the Centre for Ecological Research and Forestry Applications (Creaf), a public research institute at the Autonomous University of Barcelona. As wind blows fog through the mesh, water droplets collect and fall into the containers below.

As the wind blows the fog through the mesh, the water droplets are collected.
As the wind blows the fog through the mesh, the water droplets are collected. Photograph: Courtesy of Life Nieblas

“Fog collection is particularly applicable in restoring the Canary Islands’ laurisilva [laurel forests], which themselves exist by collecting fog water,” says Carabassa. The water droplets from the fog condense on the trees’ shiny, waxy leaves. “The system allows saplings to flourish until they are mature enough to capture water themselves,” he adds. Laurisilva is sub-tropical rainforest populated by evergreen species, though not necessarily the familiar laurel trees found in parks and gardens.

To operate well, fog collectors need both fog and wind, conditions that exist in the Canaries and Portugal, but less so in the Mediterranean, where forest fires and desertification are a growing problem.

“We’re still trying to discover what are the optimal conditions for fog collectors to work,” says Carabassa, who adds that laurisilva restoration can help to replenish the aquifers that are under constant strain in the Canaries.

As well as the Canary Islands, where Creaf is working with the Gran Canaria local authority, the public company Gesplan, which manages the project, and several other research institutes and public organisations, the technique will be tested in maritime areas around Barcelona and the El Bruc municipality in northern Catalonia, which was ravaged by a huge fire in 2015.

On Gran Canaria, the goal is to capture 215,000 litres of fog and dew water a year to repopulate 35 hectares (86 acres) with 20,000 laurel trees in the Doramas Forest, an area at high risk of desertification as a result of fires. The reforestation will be carried out with native species typical of laurisilva, including the candleberry myrtle (Myrica faya), strawberry tree (Arbutus unedo) and barbusano (Apollonias barbujana).

The fog collectors on the hillside in Gran Canaria are helping to restore laurisilva forest in areas at risk of desertification.
The fog collectors on the hillside in Gran Canaria are helping to restore laurisilva forest in areas at risk of desertification. Photograph: Courtesy of Life Nieblas

Another device being tested alongside the fog collectors is the “cocoon”, a biodegradable, doughnut-shaped container made of recycled cardboard that surrounds the hole where a seedling is planted and can hold 25 litres of water. It provides water and shelter for the seedling, at least during its first year, which is usually the most critical.

A lid reduces evaporation loss from the bowl, and the cocoon also protects the seedling from small herbivores. The cocoon is buried in the ground and is initially filled manually with water, thereafter by rainfall and, in the Canaries and Portugal, with water from fog collectors.

The cocoons have been tested in Spain, Italy and Greece, where they were planted in a variety of soils and climates alongside a control group planted in the conventional way. Both groups were initially supplied with the same amount of water and there was no further irrigation, with the seedlings monitored over two years. Compared with conventional planting systems, the cocoons increased the rate of seedling survival, especially under dry growing conditions.

A cocoon can hold 25 litres of water and also provides shelter for the seedling.
A cocoon can hold 25 litres of water and also provides shelter for the seedling. Photograph: Courtesy of Life Nieblas

Seedlings planted with cocoons showed a survival rate close to 60%, compared with 40% for those planted using conventional methods. The response of holm oaks (Quercus ilex), a key native species, was particularly positive in terms of survival and growth rate.

The cocoon was developed by the Dutch firm Land Life and is used all over the world, but the Green Link project, run by Creaf and its partners as part of the Life Nieblas project, is focused on a plantation of organic almonds in Almería, as well as reforestation schemes in Valencia, Alicante, Catalonia, Italy and Greece.

With extreme weather likely to lead to more fires, it is hoped that these techniques will speed up the decades-long process of reforestation.

“We are tackling reforestation in a more viable and effective way, acting in areas that are particularly vulnerable to climate change and desertification,” says Carabassa.

Find more age of extinction coverage here, and follow biodiversity reporters Phoebe Weston and Patrick Greenfield on Twitter for all the latest news and features


Stephen Burgen

The GuardianTramp

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