The coast already has nothing. The question is what happens next.
En las islas que el Atlántico sostiene entre África y Europa, el agua que el propio clima puede ofrecer se irá retirando a lo largo de este siglo, como una marea que no regresa. Investigadores de la Universidad de La Laguna han trazado, por primera vez con resolución de cien metros, la trayectoria de ese repliegue: temperaturas en alza, evaporación creciente y lluvias que no compensan la pérdida. El hallazgo no es solo un dato hidrológico; es un aviso sobre la viabilidad de ecosistemas, cosechas y economías enteras que dependen de un recurso que el cambio climático está silenciosamente reclamando.
- El balance hídrico climático de las Canarias —el agua que la naturaleza deja disponible sin intervención humana— descenderá de forma continua y acelerada hasta 2100, según el estudio más detallado realizado hasta ahora sobre el archipiélago.
- Las zonas costeras ya registran un balance cero, y la presión avanza hacia el interior: El Hierro podría perder entre el 50 y el 75 % de sus reservas, Gran Canaria enfrenta una depleción casi total, y Fuerteventura y Lanzarote verán menguar aún más sus ya escasas fuentes.
- Sobre ese déficit natural se acumulan las demandas humanas: una población creciente, un turismo que no cede y una agricultura que compite por cada litro en un territorio donde el agua nunca ha sobrado.
- La desalación, el reciclaje de aguas residuales y el riego eficiente existen como respuestas, pero cada una arrastra sus propios costes —energéticos, económicos, logísticos— y ninguna basta por sí sola.
- Los investigadores señalan que la precisión de los datos ya permite planificar con rigor; lo que resta por resolver no es técnico, sino político: si habrá voluntad colectiva para actuar antes de que la escasez dicte las condiciones.
Investigadores de la Universidad de La Laguna han publicado la proyección más detallada jamás elaborada sobre el futuro hídrico de las Islas Canarias. Utilizando una metodología adaptada a la compleja orografía del archipiélago y una resolución de cien metros, el equipo liderado por el profesor Juan Carlos Santamarta Cerezal ha modelado cómo evolucionará el balance hídrico climático —la cantidad de agua que el clima, por sí solo, deja disponible en el territorio— a lo largo de tres ventanas temporales hasta el año 2100.
El diagnóstico es consistente en todos los escenarios: el agua disponible disminuirá, y la caída se acelerará conforme avance el siglo. La causa es la combinación conocida de temperaturas más altas, mayor evapotranspiración y precipitaciones que se mantienen estables o retroceden. Las zonas costeras ya se encuentran en balance cero; a medida que el estrés avanza hacia cotas más altas, la presión se extiende por todo el territorio.
La situación varía en intensidad según la isla, pero no en dirección. El Hierro podría perder entre la mitad y tres cuartas partes de sus reservas actuales. Tenerife enfrentaría una reducción de alrededor del 50 %. Gran Canaria, cuyas reservas ya se concentran en pequeñas zonas montañosas del norte y el centro, se aproximaría a un agotamiento casi completo. Fuerteventura y Lanzarote, las más áridas de España, verían empeorar una situación ya crítica.
A este declive climático se suma la presión demográfica y económica: el turismo y la agricultura compiten por un recurso que mengua. El estudio reconoce que existen herramientas —desalación, reutilización de aguas residuales, riego eficiente—, pero advierte que su despliegue debe ser coordinado, alimentado por energías renovables y integrado en una planificación común entre islas y sectores. Sin esa respuesta articulada, la viabilidad de la agricultura, los ecosistemas naturales y el propio motor turístico quedaría comprometida. Los datos, por primera vez, son lo bastante precisos para actuar. La pregunta que el estudio deja abierta es si llegará la decisión política a la altura de esa precisión.
Researchers at the University of La Laguna have mapped out a troubling trajectory for the Canary Islands: the water that the climate alone can provide will shrink steadily through the rest of this century. The culprit is a familiar combination—rising temperatures, more moisture evaporating from soil and plants, and rainfall that stays flat or declines. It is the first time anyone has modeled this decline with such precision, and the picture is stark.
The study, published in Environmental Monitoring and Assessment and led by professor Juan Carlos Santamarta Cerezal, focuses on what researchers call the climatic water balance—a measure of how much water the atmosphere and earth naturally leave available to a territory, stripped of human interventions like desalination. It is a clean way to isolate climate change's direct effect on the resource. The team adapted a methodology called Ficlima to the islands' complex terrain, translating global climate models down to a resolution of 100 meters, capturing the microclimates and elevation shifts that make each valley and ridge different. This level of detail has never existed for the archipelago before.
The projections run across three time windows—2021 to 2050, 2040 to 2070, and 2071 to 2100—under different emissions scenarios, from optimistic to worst-case. What emerges is a consistent pattern: the water balance declines, and the decline accelerates as the century wears on. Altitude matters enormously. The coastal zones of the islands already sit at zero—they have no climatic water surplus at all. As conditions worsen inland, stress spreads across the entire territory.
Island by island, the story varies in degree but not direction. El Hierro, one of the western islands with the most water today, faces cuts of 50 to 75 percent by century's end under moderate to severe emissions scenarios. Tenerife looks at roughly a 50 percent reduction, equivalent to losing 50 to 100 millimeters of available water. Fuerteventura and Lanzarote, already among the driest places in Spain, will see their meager supplies squeezed further. Gran Canaria faces near-total depletion of its reserves, which today cling to small mountain zones in the north and center. The western islands will lose more in percentage terms because they start with more, but the absolute losses are severe everywhere.
Behind these projections sits a second pressure: people. The islands' population grows. Tourism demands water. Agriculture demands water. These two sectors compete fiercely for a shrinking resource. The researchers acknowledge that some tools already exist—desalination plants, wastewater recycling, better storage and distribution networks. But each comes with costs: desalination consumes energy, often from fossil fuels. Efficiency gains are real but incremental.
The study proposes a suite of adaptations. Pair desalination with renewable energy to cut the carbon footprint. Shift to irrigation techniques that waste less and crops that tolerate drought better. Coordinate water planning across the tourism sector instead of letting each resort fend for itself. Let islands and regions share resources and knowledge. Weave climate resilience into every water management decision from now on.
Without such measures, the researchers suggest, the islands face a genuine threat to their future. Agriculture could become unviable. Tourism, the economic engine, would face constraints. Natural ecosystems would suffer. With coordinated, adaptive policy—with a real commitment to sustainability—the Canaries might navigate the transition. The data is now precise enough to plan by. The question is whether the will exists to act.
Notable Quotes
The analysis offers a resolution of 100 meters, constituting the first time such detail has been available for the archipelago, based on international climate models from the UN's Sixth Assessment Report.— University of La Laguna
Adoption of adaptive policies and an integrated, sustainable approach to water management will allow the Canary Islands to better face future scarcity and ensure long-term viability of both natural ecosystems and human activities.— Study authors
The Hearth Conversation Another angle on the story
Why does this study matter more than other climate projections we've heard about?
Because it's the first time anyone has looked at the Canaries with this kind of local detail. A hundred-meter resolution means you can see how a mountain ridge changes the water picture from one side to the other. Global models can't do that. You need to know where the water actually is—or isn't—to make real decisions.
The coastal zones already have zero water balance. What does that mean in practice?
It means the coast is already living on borrowed water—from desalination, from pumped reserves, from somewhere else. The climate itself provides nothing. As the interior dries out, that pressure spreads inland. There's nowhere left to retreat to.
El Hierro loses 50 to 75 percent of its water by 2100. Is that island going to be uninhabitable?
Not necessarily uninhabitable, but it will be radically different. You can't farm the way you do now. You can't support the same population without massive inputs—desalinated water, imported food. It becomes a different kind of place, more dependent, more fragile.
Tourism and agriculture both need water. How do they choose?
That's the real question the researchers are raising. Right now, there's no integrated plan. Each sector pulls what it needs. When water gets scarce, that chaos becomes a crisis. The study is saying: you have to decide now, together, what the islands can actually support.
Can desalination solve this?
It can help, but it's not a solution by itself. Desalination plants use energy. If that energy comes from fossil fuels, you're trading one climate problem for another. Pair it with solar and wind, and you've got something. But it's expensive, and it requires constant maintenance and investment. It's a tool, not a fix.
What happens if the islands do nothing?
The study doesn't say the islands will become uninhabitable. But they'll become less viable as they are now. Agriculture shrinks. Tourism faces water rationing. Ecosystems degrade. You end up with a smaller, more constrained version of island life—unless you're willing to invest heavily in adaptation. That's the choice being laid out.