From Iceland to southern Europe, what are mosquitoes warning us about?

The arrival of mosquitoes in Iceland and their spread across Southern Europe show how climate change is transforming ecosystems and increasing risks to human health.

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In 2025, a biological discovery marked a milestone that, although discreet, resonates as an alarm across the planet: the confirmation of the presence of wild mosquitoes in Iceland. For biology, this represented a historic break; the “Icelandic exception”, the natural shield that low temperatures had provided against these species, was disappearing. What for centuries had been an insurmountable climatic barrier is now beginning to become a thing of the past.

This phenomenon is neither an isolated event nor a biogeographical curiosity. It is, in fact, a tangible symptom of how climate change is rewriting the rules of the living world. The planet’s average temperature is reaching unprecedented levels and, with every fraction of a degree of warming, ecological niches shift, allowing opportunistic species —and the pathogens they carry— to expand their range into latitudes and altitudes that were previously inhospitable.

The new reality of Southern Europe

If we look closer to home, in Southern Europe and specifically in Spain, this process is already well established. The tiger mosquito (Aedes albopictus), a vector capable of transmitting viruses such as dengue, chikungunya or Zika, is no longer an occasional visitor but a permanent neighbour. What we are seeing is not only a geographical expansion but also a change in seasonality: milder winters and longer summers allow the life cycles of these vectors to accelerate and extend.

This expansion is no coincidence. As we have documented within the framework of the Planet Hub, the combination of changes in rainfall patterns and rising temperatures creates ideal conditions for vectors that were previously confined to tropical regions to find a favourable environment in our cities and rural areas.

A global perspective on planetary health

When the biological map is redrawn in this way, the implications for planetary health are profound. The spread of dengue is perhaps the clearest example of this new era. The disease, which historically placed an overwhelming burden on tropical regions, is now challenging the health systems of countries that were not prepared to manage local transmission.

But the risk goes beyond a single pathogen. We are facing a “mixing” of biological cycles: when ecosystems that were previously separated by climatic barriers begin to overlap, the opportunities for pathogens to jump between species increase exponentially, a phenomenon known as spillover. We are entering uncharted territory where climate unpredictability translates into greater health vulnerability.

From observation to action

In this scenario, science has a dual responsibility. On the one hand, we must deepen our understanding of tipping points, or points of no return in the Earth system: critical thresholds which, once crossed, can trigger irreversible changes in the climate and, by extension, in our health. On the other hand, the urgency of the situation requires us to act: the development of early warning systems (EWS) based on robust computational models is our best tool. These systems must not only predict the climate, but also integrate patterns of human mobility, changes in land use and vector ecology in order to anticipate outbreaks before they occur.

This year, World Mosquito Day should serve as a reminder that human health cannot be separated from the health of our planet. Iceland is only the first warning; the real challenge is to understand that, in a warming world, geographical barriers no longer protect us. Resilience in this century depends on our ability to anticipate these changes and act on the underlying causes of this accelerating transformation.