It has happened again. Santa Olalla, Doñana’s largest permanent lagoon, has completely dried up. The Unique Scientific and Technology nfrastructure (ICTS) – Doñana Biological Reserve, which reports to the Doñana Biological Station (EBD-CSIC) of the Spanish National Research Council (CSIC), updated its lagoon monitoring camera a few weeks ago to track its evolution. Finally, its complete desiccation was confirmed yesterday. Since the research center began collecting data on this natural area half a century ago, this image has never been repeated two consecutive years. This testifies to the critical situation facing Doñana’s lagoon system and, consequently, all the biodiversity that depends on it.

Doñana National Park was declared a World Heritage Site in 1994 due to its variety of ecosystems and the great diversity of species that inhabit them, making it a unique natural enclave in Europe. One of these ecosystems is represented by the lagoon system, which harbors high biodiversity and serves as a refuge for several threatened and endemic species. However, in recent years, Doñana's lagoons have been suffering serious deterioration: their inundation period is becoming increasingly shorter, and many of them are no longer flooding at all. This is severely impacting the biodiversity they sustain. The drying up of Santa Olalla in summer is one of the clearest pieces of evidence of the lagoon system's deterioration, signaling the absence of vital aquatic summer refuges for the aquatic flora and fauna of Doñana’s sand dune area (manto eólico).

What the Latest Scientific Data Reveals

The ICTS – Doñana Biological Reserve, through its Monitoring Program, has confirmed that the 2021–22 hydrological cycle recorded the lowest precipitation levels in the last ten years (283 mm). The current year hasn't seen much improvement, with similar rainfall levels (337 mm up to August). Additionally, both years are registering extremely high maximum temperatures and the highest recorded average annual temperature (18.53°C).

However, these factors are not the sole cause of the lagoon system's deterioration. A study by the Doñana Biological Station published this year, using data collected over 40 years, confirms that 59% of Doñana's largest lagoons have already disappeared. This phenomenon is significantly related to the high temperatures and the prolonged period of low rainfall that Doñana is experiencing, but also to the overexploitation of the aquifer that feeds this lagoon system. 80% of these lagoons dried up earlier than would be expected given the recorded temperature and precipitation levels, and 84% were inundated less than predicted. This clearly demonstrates that human activity is disrupting the natural balance of the lagoons and exacerbating the problem.

Furthermore, it is also concerning that 19% of the lagoons that remain still have more than half of their basin area invaded by scrub and pine trees, and only 10%, primarily located in the vera area, remain in good condition. In another recently published study, the Doñana Biological Station concludes that the invasion of the lagoon basins by terrestrial vegetation is a good indicator for detecting their progressive deterioration and imminent disappearance. These symptoms are especially evident in the northwestern area of the National Park and in the lagoons closest to Matalascañas, including Santa Olalla, where dense stands of rushes are already visible in half of its inundation basin and masses of shrubs have colonized its current edges and islets.

An Ecosystem in Danger

Most of Doñana's lagoons are temporary; they flood thanks to water from the aquifer which, when recharged by rainfall, reaches the surface level, filling their basins and bringing the reserve to life. In the last decade, there have been no years of heavy precipitation, which has reduced the aquifer's recharge. This has not been enough to counteract the excessive water abstraction for consumption by the tourist town of Matalascañas during the summer and for intensive strawberry cultivation located around the park, which has increased its surface area by more than 30% in the last 10 years. All of these factors have contributed to reducing the aquifer levels, which prevents many lagoons from flooding or shortens the period they remain inundated, severely affecting the life cycles of the species that inhabit these aquatic environments.

Permanent lagoons, which retain water all year, are very rare in the park, meaning that in this temporary system they serve as a refuge for many species. Until a few years ago, only three lagoons were considered permanent: Santa Olalla, Laguna Dulce, and El Sopetón. Santa Olalla was the only one we could still consider permanent, although it reached a small inundated area and had high salt concentrations during summer. Its complete desiccation now prevents, for example, the presence of fish. When it dried up in 2022, we observed the death of the eels that remained there, a species currently under threat. We are also seeing a decline in its terrapin population.

Recommendations from the Scientific Community

The Doñana Biological Station demands an urgent reduction in the total amount of water extracted from the aquifer to levels that allow the recovery of the lagoon system and halt the degradation of the natural area. It also suggests updating the system for assessing the state of the aquifer and carrying out annual evaluations of water availability to define the maximum permitted extraction quantities and the necessary conservation measures that must be adopted.

Another of its proposals is to urgently re-establish legal governance for water management and land-use planning in the Doñana region, ensuring they comply with current legislation. Furthermore, it proposes protecting the legally operating agricultural sector from the loss of brand value for its products, unfair competition from illegal producers, and the uncertainty that threatens its future.

Also important is the establishment of the Doñana 2030 Working Commission, which was approved by the Doñana Participation Council, in order to make rapid and coordinated progress in resolving all the problems facing Doñana. These problems are not limited to the aquifer but also include water pollution and intense overgrazing, which are also affecting the natural enclave.