Researchers led by Zekang Zhang of Hebei University of Engineering, together with colleagues from the Chinese Academy of Sciences, compiled earthquake disaster records from the Emergency Events Database, known as EM-DAT, covering the period from 1980 to 2024. Unlike instrumental earthquake catalogs, which capture virtually every seismic event detected by sensors, EM-DAT records only disasters that cross specific impact thresholds, such as causing at least ten deaths, affecting at least one hundred people, or triggering a state of emergency or a call for international assistance. This impact-oriented approach allowed the team to focus not on where and when the ground shakes, but on where and when earthquakes actually devastate societies.

The temporal findings are nuanced. The number of recorded earthquake disaster events shows a statistically significant upward trend, confirmed by the non-parametric Mann-Kendall test after correcting for autocorrelation in the annual series. Yet mortality-related indicators moved in the opposite direction: the mortality rate, defined as fatalities relative to the affected population, declined significantly over the 45-year window. The researchers emphasize that this divergence does not mean earthquakes are becoming less dangerous in a physical sense. Rather, it reflects changes in how societies are exposed, how they record disasters, and how effectively they protect their populations, with several catastrophic events, including the 2004 Sumatra-Andaman earthquake and Indian Ocean tsunami, the 2008 Wenchuan earthquake, the 2010 Haiti earthquake, the 2011 Great East Japan earthquake, and the 2023 Türkiye-Syria earthquake, dominating short-term fluctuations in the data.

To test whether these patterns were artifacts of a handful of extreme tragedies, the team ran sensitivity analyses excluding the five deadliest disasters of the era. The overall temporal tendencies remained consistent, suggesting that the decline in mortality relative to population is a genuine structural feature of the record rather than a statistical shadow cast by a few outliers. The team also adjusted all economic losses for inflation using the OECD Consumer Price Index, expressing them in constant US dollars, and cross-validated their EM-DAT extraction against the independent NCEI earthquake database for overlapping years, finding consistent temporal patterns in events, fatalities, and losses.

Perhaps the most visually compelling result concerns the migration of statistical centroids, the weighted geographic centers of disaster impacts. The unweighted centroid of recorded earthquake disasters shifted eastward across three consecutive 15-year periods, jumping 1,872.4 kilometers between 1980-1994 and 1995-2009, a displacement the permutation tests found statistically significant, and then a further 770.4 kilometers into the most recent period. But when the researchers weighted the centroids by fatalities, affected population, or economic losses, the trajectories diverged dramatically. The fatality-weighted centroid, for instance, leapt roughly 11,463 kilometers between the second and third periods, from the eastern Mediterranean region to the central Atlantic, a shift driven largely by the changing geography of mass-casualty events. These divergent paths demonstrate that where earthquakes strike, where people die, and where money is lost are three spatially distinct questions.

At continental and national scales, Asia dominates nearly every cumulative measure, accounting for the largest share of recorded events, affected populations, fatalities, and economic losses, a pattern tied to its vast populations overlapping the Pacific Ring of Fire and the Alpine-Himalayan seismic belt. Yet normalized indicators tell a subtler story. Densely populated countries such as China, India, and Indonesia contribute heavily to cumulative fatalities and affected populations, while asset-rich nations such as Japan, the United States, and several European countries register disproportionately high economic losses per event. Europe, despite contributing relatively few recorded events, shows a comparatively elevated share of average economic loss per disaster, underscoring how concentrated economic exposure can amplify the financial footprint of even infrequent earthquakes.

To move beyond description, the team applied the Geographical Detector model, a statistical framework designed to quantify how well the spatial stratification of an explanatory variable matches the spatial differentiation of an outcome. For mortality measured as deaths per million residents, earthquake magnitude emerged as the single strongest factor, with a q-statistic of 0.17, followed by seismotectonic type and disaster process type, which distinguished simple earthquakes from earthquake-tsunami compound events. Socioeconomic variables such as population density and GDP per capita showed weaker but still detectable individual explanatory power. For economic losses normalized by national GDP, magnitude again led with a q of 0.19, but population density rose to prominence with a q of 0.14, confirming that economic damage tracks the geography of exposed assets as much as the physics of shaking.

The interaction analysis delivered the study’s most methodologically important insight: combinations of factors consistently outperformed any single variable. For mortality, the pairing of magnitude and population density achieved a joint q of 0.33, roughly double the explanatory power of magnitude alone, while magnitude combined with GDP per capita reached 0.27. For economic losses, the interaction between population density and GDP per capita produced a q of 0.53, the highest in the entire analysis, followed by focal depth paired with tectonic setting at 0.47. Most factor pairs exhibited bilinear or nonlinear enhancement, meaning their joint spatial stratification explained more variance than the sum or the maximum of their individual contributions. In plain terms, deadly and costly earthquakes arise where severe seismic hazard and dense human and economic exposure overlap, not where either factor is extreme in isolation.

The authors are careful to frame these results as statistical spatial associations rather than causal mechanisms, and they acknowledge the limitations inherent in disaster databases. EM-DAT’s inclusion criteria and reporting practices vary across countries and decades, and economic loss figures depend heavily on post-disaster assessments and national reporting procedures. The national scale of the analysis may also mask subnational differences in vulnerability, building quality, and emergency response capacity. Bootstrap resampling and permutation tests were used to attach confidence intervals to centroid locations and displacements, and alternative discretization schemes for the Geographical Detector analysis produced stable q-statistics, bolstering confidence in the robustness of the identified patterns.

The practical implications are considerable. Because mortality and economic loss follow different spatial logics, the study argues that earthquake risk assessment and preparedness planning should not rely on seismic hazard maps alone. Regions where strong earthquake characteristics coincide with dense populations warrant prioritized attention to human losses and emergency readiness, while areas with concentrated economic assets require strategies focused on financial resilience and infrastructure protection. As urban expansion continues to push populations into tectonically active zones, the finding that deaths are declining relative to population size offers measured encouragement, evidence that development, exposure management, and resilience planning can bend the curve of disaster mortality even in an era of rising recorded losses and mounting economic exposure.

Subject of Research: Global spatiotemporal patterns of earthquake disaster impacts and their geophysical and socioeconomic drivers, 1980-2024

Article Title: Spatiotemporal patterns of global earthquake disaster impacts from a human-Earth perspective

Article References: Zhang, Z., Qiu, Y., Ye, Y., & Xuan, C. (2026). Spatiotemporal patterns of global earthquake disaster impacts from a human-Earth perspective. Natural Hazards and Earth System Sciences, 26(10), 4807-4824. https://doi.org/10.5194/nhess-26-4807-2026

Image Credits: AI Generated

DOI: 10.5194/nhess-26-4807-2026

Keywords: earthquakes, disaster risk, EM-DAT, mortality trends, economic losses, spatial analysis, centroid shift, Geographical Detector, population exposure, seismic hazard, resilience planning, human-Earth interactions

The core observation is deceptively simple. Much of the water infrastructure in the United States, Europe and Japan was built during the mid-twentieth century, with design lives of fifty to a hundred years now expiring in large waves. The American Society of Civil Engineers’ most recent report card gives the sector grades that reflect chronic underinvestment, while the United Nations University has flagged ageing water storage infrastructure as an emerging global risk. Meanwhile, the United Nations Department of Economic and Social Affairs projects that the share of the world’s population over 65 will continue to climb steeply through mid-century, with the fastest growth in exactly the high-income countries whose networks are oldest. Two ageing curves, one physical and one human, are converging, and the authors contend that engineering asset management alone cannot capture what that convergence means.

The ISAG framework defines the gap as the mismatch between the ageing trajectory of water systems and the evolving needs, capacities and vulnerabilities of the populations those systems serve. The team identifies four interconnected pathways through which the gap emerges. The first concerns escalating demand for reliability: older residents, people with chronic illness and those with limited mobility are far more vulnerable to service interruptions, boil-water advisories and pressure losses. A single-day outage that is an inconvenience to a young, healthy household can become a medical emergency for a dialysis patient or an elderly person living alone. When the customer base ages, the same infrastructure failure produces disproportionately worse human outcomes.

The second pathway runs through the workforce. Water utilities face a well-documented retirement wave among operators, engineers and skilled tradespeople, which compounds the physical ageing of the assets themselves. The tacit knowledge needed to keep a fifty-year-old pumping station running often lives in the heads of workers approaching retirement themselves, and shrinking labour pools in shrinking regions make recruitment harder. The third pathway involves fiscal capacity. Communities with ageing populations often have contracting tax bases and rising social spending commitments, leaving less room for the capital investment that renewal demands. In Japan, where the Ministry of Land, Infrastructure, Transport and Tourism has documented widespread consolidation of small water utilities, the arithmetic of many elderly ratepayers supporting vast buried asset stocks has already become unsustainable for hundreds of small systems.

The fourth pathway is institutional and social: ageing populations can be less able to engage in the public processes, emergency preparations and adaptation planning that resilient water governance requires, and older neighbourhoods are often the ones served by the oldest mains and service lines. The authors organise these four pathways into what they describe as an infrastructure–society ageing decline spiral, in which deteriorating service quality drives out younger and more mobile residents, eroding the fiscal and workforce base still further and accelerating deterioration. Once that spiral takes hold, they argue, conventional repair cycles cannot keep pace, and the gap widens year after year.

To quantify the scale of the problem, the team draws on a broad body of official data: the American Society of Civil Engineers’ infrastructure assessments, Water UK’s economic analysis of asset maintenance and replacement, the Japanese ministry’s reform reviews, the US Army Corps of Engineers’ national levee database, the International Commission on Large Dams’ world register, OECD infrastructure investment outlooks, US Census Bureau demographic estimates and the UN’s world population prospects. A global dataset compiled by Zhang and Gu, published in Scientific Data, provides country-level indicators of infrastructure age. None of these sources alone links demography to infrastructure condition; that synthesis is precisely what the ISAG framework is meant to supply.

The proposal’s practical punchline is a pair of contrasting planning approaches. The first is demographic-blind investment, the status quo in most jurisdictions, in which renewal schedules are set purely by asset condition and risk scoring without reference to who lives downstream, downstream of the pipe, or behind the levee. The second is demographic-aware planning, in which intervention priorities, design standards and resilience investments are adjusted according to the age structure and projected demographic trajectory of the served population. Under the demographic-aware approach, an ageing service area would pull forward replacement of assets whose failure carries high public health consequences, justify higher redundancy in distribution networks serving vulnerable populations, and tilt investment toward measures such as backup power, pressure management and rapid response capacity.

The authors are careful to say the framework is a decision-support concept rather than a formula. Its value, they suggest, lies in making an invisible coupling visible: utilities that benchmark their asset age against demographic projections, and integrate social vulnerability data into risk models, will make different and better-targeted choices than those that do not. The framework spans the full infrastructure life cycle, from planning and design through operation, maintenance, rehabilitation and eventual decommissioning, and the authors argue that demographic ageing should be treated as a first-order design parameter on the same footing as hydrology, hydraulics and structural condition. That represents a significant cultural shift for a profession whose textbooks have historically treated the human population as a static demand number rather than a dynamic, ageing system in its own right.

The timing of the Comment is deliberate. It forms part of a series contributing to the 2026 UN Water Conference, supported by UNU-INWEH as part of the UN-Water initiative to ground water policymaking in evidence. With governments preparing national water security strategies and capital programmes running into the hundreds of billions of dollars, the authors hope the ISAG framing will find its way into regulatory guidance, utility asset management plans and international lending criteria. The stakes, they note, are not merely economic. A water system that fails its most vulnerable users fails everyone’s trust in it, and rebuilding that trust after crises is far more expensive than preventing them. The authors declare no competing interests, and correspondence for the work is handled through Tufts University’s Department of Civil and Environmental Engineering.

What the paper ultimately offers is a reframing: the water crisis of ageing infrastructure is also, unavoidably, a social and demographic crisis. Pipes and people are growing old together, and the institutions responsible for water must learn to plan for both at once. If the authors are right, the utilities, ministries and municipalities that internalise this coupling earliest will be the ones that keep taps running safely for the populations that depend on them most.

Subject of Research: A framework for integrating demographic ageing into water infrastructure planning

Article Title: To fix ageing water infrastructure, we must plan for an ageing population

Article References: Vahedifard, F., Azhar, M., Li, J., AghaKouchak, A., Brown, D. C., Marfeo, E., Null, S. E., Spearing, L. A., & Tajik, N. (2026). To fix ageing water infrastructure, we must plan for an ageing population. Nature Water, 4(9), 1062-1067. https://doi.org/10.1038/s44221-026-00711-z

Image Credits: AI Generated

DOI: 10.1038/s44221-026-00711-z

Keywords: ageing water infrastructure, infrastructure-society ageing gap, demographic ageing, water utilities, water governance, asset management, Nature Water, resilience planning, public health, UN Water Conference, vulnerable populations, infrastructure life cycle