On 13 November 1985, Nevado del Ruiz volcano in Colombia erupted, melting part of its ice cap. As a result, lahars — flows of volcanic mud and debris — swept down river valleys, causing over 20,000 casualties1,2,3. Forty years after this event, natural hazards continue to claim thousands of lives around the world each year4. While the human and economic toll remains high, research has led to a better understanding of both natural hazards and the ways to respond to them. In this Focus issue, we highlight the advances, and lingering challenges, in understanding volcanic and other natural hazards and how to best mitigate their associated risks.

Credit: Richard Roscoe / Stocktrek Images / Alamy

Although the eruption of Nevado del Ruiz was preceded by signs of unrest, the institutional response to these was limited, and the population at risk was not informed or evacuated in time1. Following the eruption, lahars reached communities located tens of kilometres away from the volcanic vent, including the city of Armero, which accounted for the majority of the fatalities. Social, economic, and political factors contributed to the disaster and exposed critical gaps in Colombia’s institutional hazard preparedness and public risk awareness. Furthermore, it catalysed a wider reckoning with how volcanic risks are assessed, mitigated, and communicated.

In a Q&A in this issue, natural hazard researchers discuss the role of institutions and decision-makers in creating effective policies for hazard assessment, mitigation, and response. However, the Q&A highlights persistent shortcomings in institutional capacity to effectively manage risks and respond to disasters.

Moreover, hazards may trigger secondary events, resulting in cascading effects5. The incidence of these is increasing in mountainous regions in particular, as Fan and colleagues note in a Correspondence. The authors call for policy frameworks to be updated, shifting the perspective from managing hazards individually to developing a multidisciplinary approach.

Meanwhile, a Comment by Calvache discusses Colombia’s successful transformation in managing volcanic and other natural hazards since Armero. The author emphasizes the importance of new policies designed to ensure scientific knowledge is properly transmitted to and assimilated by populations at risk. They also note improvements focused on enhancing institutional and societal capacity to recover and adapt after disasters.

However, the effectiveness of institutional actions and policies depends on the communication of information to communities at risk, as Mani and colleagues explore in a Comment. The authors argue that good hazard communication should be accurate, inclusive, and timely. They also emphasize that it must overcome the challenges that come with natural hazards, such as hurdles arising from local socio-economic and cultural factors.

Knowledge co-creation with populations that live in areas at risk, such as Indigenous communities, is also important and can build trust that facilitates risk communication. As Calder and colleagues highlight in a Comment, attempts to include Indigenous knowledge in disaster risk reduction have increased. Nonetheless, they remain mostly aspirational and face challenges, such as overcoming hierarchical dynamics that create barriers to equitable participation and knowledge exchange.

Ultimately, risk communication and mitigation need to advance together with scientific research on hazards. However, despite considerable advances in understanding and monitoring lahars since the Armero disaster, their diverse triggers and spatiotemporal unpredictability continue to hinder our ability to fully grasp their dynamics and the threats they pose, as discussed in a second Q&A.

Since the eruption of Nevado del Ruiz, research and institutional agendas have advanced natural hazard management and risk mitigation, but a greater appreciation of the geographical, cultural, and socioeconomic context in which such hazards occur is still needed. Only with these in mind will it be possible to avert another tragedy like Armero.