Island Communities and Satellite Records Tell a Shared Story of Storms, Runoff and Reef Fish Poisoning

On Ambae Island, a volcanic island in the Vanuatu archipelago of the southwest Pacific, the people who live closest to the reefs have long reported changes they can see with their own eyes: heavier downpours, fiercer cyclones, muddier streams running onto the fringing reef, and fish that increasingly make them sick. A new study led by Allan Rarai of the University of the South Pacific and the Vanuatu Meteorology and Geo-Hazards Department, together with Eberhard Weber, Philip Obaigwa Sagero and Meg Parsons, has now tested those local observations against more than four decades of satellite-derived environmental records. The research, published in the journal Regional Environmental Change, examines how community perceptions of climate variability, land-use change and reef degradation align with observed rainfall and tropical cyclone data for the period 1981 to 2023, and explores how these environmental pressures connect to cases of ciguatera fish poisoning, one of the most common climate-sensitive illnesses in the Pacific.

Ciguatera fish poisoning is caused by ciguatoxins, potent neurotoxins produced by benthic dinoflagellates of the genus Gambierdiscus and related organisms that grow on dead coral and macroalgae in tropical reef ecosystems. The toxins accumulate in herbivorous reef fish and pass up the food web to large predatory species that are a staple of island diets. Disturbances that create fresh surfaces for dinoflagellate colonisation, such as cyclone damage to coral or sediment and nutrient pulses from land, can therefore increase the abundance of toxigenic organisms and raise the risk of poisoning. Because there is no routine test for ciguatoxin in fish sold or caught for local consumption, island communities depend heavily on their own environmental knowledge to judge when and where fish are safe to eat.

To capture that knowledge, the researchers conducted structured interviews with 37 long-term residents of Ambae, asking them to describe changes in rainfall, tropical cyclones, land use, runoff and reef conditions over their lifetimes. The interview responses were then compared with MERRA-2 reanalysis rainfall data, the Modern-Era Retrospective Analysis for Research and Applications, version 2, produced by NASA, along with tropical cyclone records for the southwest Pacific and provincial-level ciguatera case data in which Ambae cases dominate. This dual approach, pairing perceived change with measured change, is a recognised method for validating local observations and for identifying where memory, experience and instrumentation diverge.

The comparison produced a striking pattern of convergence on intensity and divergence on frequency. Residents overwhelmingly perceived that rainfall had become more intense and that cyclones had grown stronger, and these perceptions broadly matched the observed record, which shows increasing rainfall variability and rising cyclone intensity across the study period. When it came to how often cyclones strike, however, perceptions diverged from the data: community members tended to believe cyclones were becoming more frequent, while the observed records did not show a matching upward trend in frequency. The authors attribute this gap to the psychology of high-impact storms, in which memories of devastating events such as Cyclone Funa, which struck Ambae in January 2008, and Cyclone Pam in 2015, anchor perceptions of frequency around the most traumatic experiences rather than the full statistical record.

This memory effect has practical consequences. Risk perception research has repeatedly shown that experience of extreme events shapes how communities prepare, adapt and respond, and the Ambae findings reinforce the point that perceived frequency can be inflated by salient disasters even when the underlying hazard statistics remain more stable. For disaster risk managers in Vanuatu and other small island developing states, the message is that community early-warning knowledge is reliable for intensity and impact but should be complemented by objective monitoring when it comes to frequency-based planning, so that adaptation resources are allocated according to actual hazard profiles rather than recollection alone.

The second strand of the study turned to health. Using exploratory statistical analysis, the researchers examined whether annual ciguatera case counts were more closely associated with rainfall anomalies or with tropical cyclone activity. The results pointed clearly toward cyclones: years with greater cyclone activity were more strongly linked to elevated case counts than years with unusual rainfall. This is mechanistically plausible, since cyclones deliver a double disturbance, physically shattering coral structures that dinoflagellates readily colonise and dumping large pulses of terrestrial sediment, nutrients and organic material onto nearshore reefs through intensified runoff. Studies from other Pacific islands, including Rarotonga in the Cook Islands and reef systems in American Samoa and Palau, have documented similar ridge-to-reef pathways in which catchment disturbance and storm runoff degrade benthic habitat and alter the ecological conditions that favour toxigenic dinoflagellates.

The authors are careful to stress the limits of causal inference. The ciguatera case series is short, recorded only at annual resolution, and compiled at a coarse provincial scale dominated by Ambae cases, which means the analysis cannot isolate the exact timing and location of exposures or control for changes in reporting practice, health-seeking behaviour and island population movements. Ambae’s own recent history complicates the picture further: the Ambae volcano erupted in a Plinian episode during 2017 and 2018, forcing the evacuation of the entire island population and disrupting both land use and fishing patterns. Volcanic ashfall, deforestation and displacement all interact with climatic stressors in ways that a short annual case record cannot disentangle, and the researchers explicitly frame their ciguatera findings as indicative associations rather than proof of causation.

Even so, the study’s central contribution is methodological and quietly transformative. It demonstrates that community knowledge and satellite-based environmental monitoring can be systematically combined to identify plausible ridge-to-reef pathways linking climatic disturbance, land-use change, reef degradation and climate-sensitive disease risk. Earlier work by the same lead author, published in Communications Earth & Environment in 2024, showed that Indigenous knowledge in Vanuatu, combined with scientific observation, can function as an early warning system for ciguatera outbreaks. The new research strengthens that foundation by quantifying which components of community observation are most trustworthy, and by anchoring them in a 43-year environmental record that no single resident could hold in memory.

For the people of Ambae, where reef fish remain central to nutrition, livelihoods and cultural practice, the stakes of this research are immediate. Ciguatera is the most widely reported marine food-borne illness in the Pacific islands, with tens of thousands of cases recorded regionally over recent decades, and its burden falls disproportionately on communities with the least access to laboratory diagnostics. Understanding that cyclone years may seed conditions for later poisoning outbreaks gives health authorities a possible window for targeted public health messaging, and gives fishing communities a scientific echo of the traditional knowledge they already apply when deciding whether a reef is safe. As climate change continues to intensify extreme rainfall and cyclone behaviour across the southwest Pacific, integrating local observation with environmental records offers small island communities one of the few practical tools available for anticipating a hazard that hides inside an otherwise valuable food source.

The research also carries a broader message for climate adaptation science. Perception studies conducted across Africa, Asia and the Pacific have often found mismatches between what communities observe and what meteorological records show, and those mismatches are frequently used to question local knowledge. The Ambae study flips that framing, showing that local observation can be highly accurate where it matters most, for intensity and impact, and that apparent errors are themselves informative about how humans experience and remember environmental risk. In an era when monitoring infrastructure is sparse across much of the Pacific, the residents of small islands are, in effect, a distributed sensing network, and this study shows how their observations can be calibrated against, and combined with, the satellite record to protect both ecosystems and human health.

Subject of Research: Community perceptions of climate variability, land-use change and ciguatera fish poisoning risk on Ambae Island, Vanuatu, compared with observed rainfall and cyclone records

Article Title: Community perceptions and observed environmental records of climate variability, land-use change, and ciguatera fish poisoning risk on Ambae Island, Vanuatu

Article References: Rarai, A., Weber, E., Sagero, P. O., & Parsons, M. (2026). Community perceptions and observed environmental records of climate variability, land-use change, and ciguatera fish poisoning risk on Ambae Island, Vanuatu. Regional Environmental Change, 26(4), Article 193. https://doi.org/10.1007/s10113-026-02686-9

Image Credits: AI Generated

DOI: 10.1007/s10113-026-02686-9

Keywords: ciguatera fish poisoning, Vanuatu, Ambae Island, climate variability, tropical cyclones, rainfall, land-use change, coral reefs, community perception, MERRA-2, ridge-to-reef, Pacific Islands