Investigation Climate change in southern Europe | Southeastern Spain
Typical landscape of Tabernas desert, Spain | Davide Mancini

Europe’s desert mirage: how olive-oil fever is drying out Spain’s ancient aquifers

Past droughts forced the Romans out of southeastern Spain. The Arabs adapted to the little water available. Today’s industrial olive-oil production, added to climate change, is putting ancient engineering under huge pressure and causing desertification. This article is part of a series on the impact of climate change on Southern Europe – a thematic chosen by Voxeurop members.

Published on 13 September 2021 at 14:11
Typical landscape of Tabernas desert, Spain | Davide Mancini

The vegetation growing along the acequia is thick and the sunlight barely seeps in through the canes and leaves above our heads. Just a few meters away, beyond the bushes, the temperature is hitting 40°C.  It is hard to stand in the sun. The rocky walls of the canyon, where the Rio Agua springs forth, reveal constant patterns of shiny gypsum, the white crystal that characterised this karstic area and its network of caves and underground channels. Some kilometers away from the desert of Tabernas, in southern Spain, the Aguas river creates a unique oasis with a variety of native species, like the Greek Tortoise and the Spanish pond turtle

The word acequia comes from the Arab al-sāqiyah, meaning irrigation channel, and it is still used in Spanish language to refer to open-air water channels that distribute natural spring water for agricultural and domestic use. The one in Los Molinos del Rio Agua is the only water source for the few inhabitants living in this repopulated village. Santos is the acequiero of the community, responsible for the maintenance and clearing of the watercourse. Here there are about twenty houses still inhabited, mainly by people who decided to live off-grid, meaning that they produce their own domestic electricity with solar panels and manage their only water source, the river, without depending on the local municipality. When we arrive at the end of the acequia, Santos shows me a little door carved into the rock, which is where the water emerges.

This human-made cave is thought to be even older than the acequia system developed by Al-Andalus’s engineers, and it may date back to Roman times. Several requests were made to the regional municipality to identify the exact historical record of the cave, but no study has been made yet. It is nevertheless certain that Romans occupied this area of the Iberian peninsula about 2,200 years ago, and that the environment around was much more flourishing than what the Arabs found centuries later. 

The modest water stream is nothing impressive, but it is one of the rare perennial rivers of the area, the driest region in continental Europe. The continuity of the stream guarantees the existence of this European oasis, and its willows, white poplars and oleander. But researchers as well as environmental activists warn that the river could soon disappear, cutting off essential water for Los Molinos and the other villages found along its path towards the Mediterranean sea. The expanding olive-tree plantations nearby seem to have a direct impact on the underground aquifer, where the Rio Aguas springs from. In 2000 the volume of water flowing from this spring was recorded to be 40 liters per second. It had dropped by 7.28 in 2020. This time period coincides with a substantial expansion of olive tree orchards nearby.

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At the edge of the Tabernas desert, in the 1970s, there were 400 hectares covered by olive trees. Today, there are about 4,400 hectares, and 1,550 of these are on a super-intensive regime. The olive tree is widely known to be a Mediterranean crop that needs little water, and it wouldn’t normally need irrigation at all. But developments in agroindustry found innovative ways to boost quantitative production. Or, the Jevons Paradox may apply: "as technological improvement increases the efficiency with which a resource is used, an increase in the consumption of that resource is more likely than a decrease".

From 65 to 100 trees per hectare traditionally planted in this area, the production was scaled up to 210, and in super-intensive plantations there are up to 1,500 trees per hectare. The quality of the olive oil is much lower than in the traditional product once sold as ‘Desert’s Gold’, and the little space between the trees make the orchard unsustainable, as the trees will become less productive once grown, in 10-15 years time.

The different olive tree plantations density and view of the typical land patterns.

The production of olives depends on exhaustive water extraction from the aquifer – a study published by the journal Land estimates that between 14 to 20 hm3 (million cubic meters) per year are needed to make this production possible. On the other hand, the aquifer can replenish only 5 hm3 per year. The regional government has also recognised the deficit between water pumped and the natural replenishment ratio - it is currently at 3.3 while the objective for 2027 is 0.7, making the basin currently overexploited by 230%.

Although an extreme one, this climate is an example of what other arid and semi-arid areas in southern Europe might become due to climate change in the Mediterranean, which is set to bring less yearly rainfall in fewer but more torrential bursts.

Manolo Pérez Sola, an environmental activist and member of the ecological platform Acuíferos Vivos, says that the aquifer of Sorbas/Los Molinos is one of the most overexploited in Spain: ”They are extracting more than the double amount of water needed to recharge the aquifer. Some experts estimate that, in this way, it may disappear within ten years.”

In 2016, two other members of the platform Acuíferos Vivos – Grupo Ecologista Mediterraneo and Ecologistas en Acción –  sued one of the companies involved with the intensive olive cultivation, Castillo de Tabernas, for extracting 464 millions of cubic meters of underground water without a permit. The company was eventually fined €450,000.

The Aguas river flowing near Los Molinos de Rio Aguas. | Photo: Davide Mancini.

The average rainwater here is very scarce – 250mm per year – and the vast majority of this water falls in two or three big rains during the year. The dry soil of Tabernas does not absorb much of the water that runs away in torrential rivers towards the sea, often generating floods. Although an extreme one, this climate is an example of what other arid and semi-arid areas in southern Europe might become due to climate change in the Mediterranean, which is set to bring less yearly rainfall in fewer but more torrential bursts.

The average yearly temperature in this area has risen by 1.6°C during the last 60 years, with a peak of 2.3° in 2015. This has added further stress to vegetation, with higher levels of water evaporation and less percolation towards the underground aquifer. Official studies by the Ministry of Agriculture and Environment in Spain, published in 2017, confirmed that the insufficient replenishment of Spanish underground aquifers is set to worsen, going from a current average rate of -3% per year to -24% towards the end of the century.

The case of Tabernas olive industry and its environmental consequences are an emblematic example of desertification in southern Europe. However, Tabernas shows that desertification does not necessarily imply desert, but rather what the UN Convention to Combat Desertification defines as “land degradation in arid, semi-arid and dry sub-humid areas resulting from various factors including climatic variation and human activity”. The green carpet of olive orchards are indeed deceptive, but they are irreversibly consuming the groundwater of this delicate ecosystem, and changes in rainfall and temperatures are only accelerating the trend.

In the area of Sorbas and Los Molinos the high concentration of gypsum creates a karstic environment that clearly shows the passage of water through millennia in its underground caverns. It is inside a cave, a few kilometers away from Los Molinos, that Fernando Gázquez and four other researchers coordinated by Jose Maria Calaforra conducted a paleoclimatic study on a stalactite. It reveals how water scarcity might have been a determinant factor in the abandonment of this area centuries ago. By analysing the traces of water molecules captured by the gypsum, the study revealed that when Romans arrived in the area the climate was experiencing much wetter conditions than today, favourable for crops and agricultural activities. “This is the first study on historical climate conducted on a gypsum stalactite, and it opens the possibility to use such material to obtain paleoclimate information in other parts of the world where karstic caves are present, like in Mexico, Italy, the US and Australia”, says Gázquez.

 The inside of Sima Blanca cave, where a stalactite was removed from to study paleoclimatic trends. | Photo: Francisco Hoyos.

After the Second Punic War, which saw the Romans defeating Carthage and occupying southern Spain around 200 BCE, the climate was probably optimal for agriculture, much more than today. In this period, the analysed stalactite already existed and was growing, capturing the information collected by the little drops filtering through soil to the underground cave. The research reveals that the maximum expansion of the Roman Republic in the Hispanic peninsula coincided with a more favourable climate that allowed vast cultivation of cereal, vine and olive.

This data was crossed with other studies conducted on samples contained in lake sediments in the nearby Sierra Nevada.These revealed traces of human activities during the studied period, such as mining and deforestation. But from 100 BCE to 500-600 CE the area recorded a drying trend, perhaps due to heavy deforestation or other climatic factors that caused droughts and therefore a more difficult environment to live in. These more extreme weather events coincided with the so-called Migration Period, and the abandonment of the Iberian Peninsula by the Romans.

Although there were many other factors - political and social - that caused the fall of the Roman Empire, it is more than symbolic to consider that climatic changes, combined with human activities, might have contributed, in this case as in others, to the end of human settlements in a region. Centuries later and despite much technological progress, a shortsighted approach to agribusiness might bring similar consequences for the inhabitants of Los Molinos del Rio Aguas,nearby villages and even towns like Sorbas, if the available groundwater is not preserved.

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