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Heated debate: a resident of Montserrat discusses a deal offered to inhabitants of the island by the British government last summer, as ash and steam. billow from the Soufriere Hills volcano behind. Volcanologists on the island, criticized by residents for their poor forecasting of eruptions, say it proved difficult to convince those who have lived safely in an area all their lives that it had become dangerous. Credit: AP/CHRIS BRANDIS

Scientists on the Caribbean island of Montserrat lost credibility in the eyes of the island's inhabitants by wrongly predicting when its volcano would erupt during 1996 and 1997, according to a survey of the island's residents.

The survey is due to be published within weeks, and could have a significant impact on debates about the role of science communication in disaster management policy.

David Sanderson, a researcher at the Oxford Centre for Disaster Studies and co-author of the survey, says the island's residents were disappointed when scientists made mistakes, and were confused by their use of complicated jargon when explaining the volcano's activity.

Sanderson says that the scientists were not only expected to know in advance when the volcano would erupt, but also to communicate this information in layman's terms.

The British government commissioned the survey in the aftermath of major volcanic activity last year. More than 20 people died trapped in their homes, despite daily warnings to leave the area. Preliminary findings were revealed at last week's annual meeting of the Geological Society of London.

Stephen Sparks, professor of volcanology at the University of Bristol and chief scientist at the Montserrat Volcano Observatory, accepts that mistakes were made, and that scientists working in disaster situations need help communicating risk information.

“Volcanology is an uncertain science,” he told the meeting. “There are aspects we do not understand. But we are not trained to communicate doubt and uncertainty.” Sparks added that scientists need feedback from the public as well as “help from people like sociologists and disaster managers”.

The findings of the survey also have implications for the role of scientific advice to governments involved in disaster situations. Some scientists at last week's meeting said privately that their task of communicating information about risks was further complicated by the lack of a disaster preparation plan, as well as by politicians' unrealistic demands on their expertise.

Montserrat is a small island 11 miles long. The volcano is in the south, and has been quiet for much of this century. Volcanic activity was renewed in July 1995. Much of the south, where most people lived, is now covered in ash following the 1997 eruption. Most of the island's 12,000 residents have been evacuated; the rest are now in the safer north. The volcano is now relatively quiet.

Local criticism of the observatory stems from the scientists' patchy record in predicting eruptions, and the direction of the flows of hot ash and magma — known as pyroclastic flows. The observatory's staff failed to predict the explosion of magma on 17 September 1996, which caused a 40,000-feet high plume of ash, and deposited 600,000 tonnes of ash on the south of the island.

Their prediction of a similar eruption in December the same year turned out to be a false alarm. Residents who had been evacuated were sent back to their homes.

Six months later, more than 20 people died in and around their homes during a third major eruption in June 1997. Sparks says an evacuation order warning of this eruption had been given months in advance. “We don't really understand why people were still in there against official advice.” One possible reason, says Sanderson, is that people were reluctant to move to the less developed north of the island.

Sanderson says that many of the island's residents said they felt the scientists' prediction record was sometimes no better than their own. Islanders said that generations of residents had monitored the volcano all their lives, and had observed changes in rockfalls, pyroclastic flows, sea level, humidity and animal behaviour.

They wanted scientists to tell them more than they already knew. “I still believe that the scientists do not have the capability to alert us when it's needed,” said one resident. “You have to alert yourself.”

The survey also revealed that there was widespread confusion about the eruption warning system put in place by scientists and the local authorities, as well as tensions between scientists and the authorities over the nature of this warning system.

The system used sirens to alert residents of an impending eruption, daily newspaper and radio reports by scientists, and maps agreed by government and scientists indicating the risks in different areas.

But survey respondents voiced dissatisfaction with most of these methods, and relied instead on information passed by word of mouth. The radio reports were considered by some to contain too many technical words. And the ‘risk maps’ introduced after the September 1996 eruption to educate people about the level of risk caused much confusion, and had to be simplified.

The early maps divided the island into seven zones, each with one of six different levels of risk, or ‘alert level’. The maps were updated six times as data changed.

Sanderson says this level of detail baffled residents, and the maps were simplified to just three zones as the volcano became more active. Many islanders were unaware of the existence of the earlier maps. Others did not know which zone they lived in. Some were unaware of changes to the status of their zones. “Eighty-eight per cent of respondents in a zone previously considered ‘unsafe’ did not know that this had changed to a zone considered highly dangerous,” says Sanderson.

“All this talk of zoning is confusing the man on the street,” said one respondent. “All these words such as ‘progressive gravitational induced collapses’, and pumice falls and all this — what does it mean?”

The risk maps had to be cleared by the authorities, and scientists and politicians had differing views on what they should contain. Richard Robertson, of the Seismic Research Unit at the University of the West Indies, says that scientists favoured simpler maps. But the authorities insisted on ‘micro-zonation’, as they did not want to evacuate the whole of the south, even though the scientists themselves were not sure of the accuracy of their predictions.

The question of whether scientists could forecast the timing and direction of pyroclastic flows to within a margin of error of metres is a “moot point”, says Geoff Wadge of the University of Reading, who also worked at Montserrat. He says scientists were never forced to do anything. But he acknowledges “pressure to do micro-zonation”.

Wadge says that, despite its failings, micro-zonation at Montserrat had its uses. He says that the authorities there have a difficult job. They need to balance the desire not to destroy a stable community with that of public safety. A complete evacuation and no eruption would have damaged the economy, but allowing people to live as normal might have led to many more deaths.