Researchers from the Department of Edafología y Química Agrícola at the University of Jaen, led by Julio Calero, warn that the olive groves in Jaén are losing, on average, 9.34 tons/hectare per year of soil from the Upper Guadalquivir Basin, which covers approximately half of the province’s area. These data indicate that average soil losses are far greater than the natural regeneration capacity (estimated at a maximum of 5T/ha per year).
Soil is a valuable resource that naturally undergoes erosion through rain or wind, but human activities double its severity. The province of Jaén ranks among the top in Spain for soil loss due to olive cultivation, soft lithologies, steep slopes, sparse vegetation cover, and phytosanitary treatments. This is a silent ecological alarm that impacts both olive grove yields and the immediate economy of farmers. Unhealthy soil ceases to perform its role in capturing greenhouse gases or regulating hydrological cycles. Additionally, the loss of fertility for farmers who face erosion in their fields results in financial costs.
As set forth in the Soil Surveillance Law, which is about to be approved by the European Parliament, "States and administrations must certify the health of soils and ensure the implementation of sustainable management practices necessary for their improvement." The most current effects of these erosion processes are the alteration of ecosystem services: carbon dioxide emissions, reservoir siltation, worsened flooding, or biodiversity loss. The situation is aggravated by the appearance of more gullies—large ditches usually created by water flows—that strip the roots of olive trees. According to studies by Calero’s research group (such as the 1:25,000 scale map of La Higuera, among others), since 2009, there has been a 146% increase in the number of gullies, an 87% increase in length, and a 78% increase in width.
"In some areas, the gullies and ravines have suffered a vertical excavation of more than 10 meters during this period. The data is impressive, honestly," the expert analyzes. The gullies negatively affect the surrounding area, reducing agricultural land, damaging infrastructure downstream, and lowering the groundwater levels of nearby streams.
Despite all of this, the evolution of soil erosion data from 2011 to 2022, as seen on the map, shows a positive outlook, as soil loss has been significantly reduced. This achievement has been made possible by increased awareness among farmers, with more and more adopting good practices, as well as regulatory impositions (such as the eco-schemes under the CAP).
"Although there is still much work to be done, the use of vegetation cover, pruning shredding, and other preventive measures are increasingly widespread. Despite this, according to recent data, less than a third of olive groves in Jaén use vegetation cover. In many cases, this is not due to the farmer’s lack of concern, as many want to implement the cover, but rather due to the state of soil degradation, which prevents it from growing. In my opinion, it is the responsibility of public administrations (including the University) to transfer the knowledge and technology needed to overcome these problems," says Calero.
Currently, European Union-funded research projects are being coordinated to address these challenges faced by farmers. For example, projects such as Sustainolive, Soil-O-live, and notably, Livingsoill. "The latter is dedicated to the creation of an Andalusian Soil Laboratory that brings together a wide range of stakeholders related to olive cultivation, so the impact on the region will likely be very significant. The goal of the Andalusian Living Lab is to prevent erosion and improve the health of olive grove soils, while always considering economic sustainability and, therefore, the long-term continuity of the Lab after the project ends," the researcher points out.
The most affected areas are the Sierra Sur, followed by La Loma and Las Villas, and then the Sierra de Cazorla. On the other hand, the least affected areas are the Campiña Norte and the Comarca Norte. Municipalities such as Villacarrillo, Villanueva del Arzobispo, Beas de Segura, Chilluévar, Frailes, and La Puerta stand out, according to the latest data from the "Soil Loss Estimation Statistics in Andalusia" by the Regional Government, 2022, updated in 2024.
This is due to the topography, the type of predominant geological material and soil, and the extent of olive groves in the municipality, which results in some towns having much higher erosion rates than others. "Almost half of the province of Jaén is covered by olive groves, and unfortunately, it is one of the crops most affected by erosion (according to INES, the average erosion of olive groves is 31T/ha per year, double the provincial average). For this reason, as INES recognizes, Jaén is one of the provinces with the highest erosion rates in Spain," says Julio Calero.
Fuente: jaenhoy (03/03/2025)
