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Spain: Volcanic material for cultivation in arid lands

In an article published by "Geology Today", four scientists from the University of Las Palmas de Gran Canaria (ULPGC) and five from the Swedish University of Upsala have reported the changes experienced in Lanzarote after the longest eruption in Europe (2,056 days) and how its agriculture took advantage of the volcanic material.

In a communiqué, the ULPGC recalled that the eruption of the Timanfaya covered 23 percent of Lanzarote with lava and ashes between 1730 and 1736, and that this later led to an agricultural revolution that allowed an island as dry as the Sahara to double its population within 40 years; a "miracle" that the study of the two universities now suggests could be exported to other arid areas.

The multiple volcanoes that opened in those six years spewed up to five cubic kilometres of incandescent materials, which buried 26 villages and many of their best fields, forcing hundreds of Lanzarote residents to emigrate in 1731.

However, four decades later, Lanzarote doubled its population. It went from 5,000 inhabitants in 1730 to 10,000 in 1768. The crops produced could even be exported and vineyards were planted for the first time.

The scientists who signed this article, including Francisco Pérez, Juan Carlos Carracedo, Alejandro Rodríguez and Valentín R. Troll, from the Institute of Environmental Studies and Natural Resources (ULPGC), stressed that Lanzarote owes its agricultural revolution, which sustained the island's economy until well into the twentieth century, to the eruption of the Timanfaya.

It is said that the bishop sent by the Crown to Lanzarote to assess the damage caused by the volcano, Manuel Dávila and Cárdenas, found that in the fields where the layer of cinder that covered the earth was thin, the plants not only survived, but grew with more vigour and in much greater quantity.

Other historians do not deny the bishop's insight, but assure that there are indications that agricultural producers in Lanzarote already used the "sanding" technique before the Timanfaya eruption, and that it had spread across the Canary Islands and much of Latin America. This technique consisted in the covering of the farm land with a thin layer of lapilli or ash.

The authors of the article stress that, without the need for irrigation, "sanding" gave a boost to the harvests on an island with a rainfall regime similar to that of the Sahara (an average of 150 litres per square metre per year), and this was possible thanks to the special properties of the volcanic materials, which retain the air's humidity and release it, little by little, to the soil where the crops are planted.

At the same time, they also protect the soil from the impact of the sun and evaporation and slowly provide nutrients without the need for other fertilizers thanks to the communities of microorganisms that settle in the cinders.

The authors of this work suggest exporting this century-old Canary technique to help cultivate other places in the world as arid as Lanzarote where, without the help of volcanic cinder, it would take "thousands of years" for their soils to become fertile.

Source: EFE

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