SANTIAGO XALITZINTLA, Mexico — When the Popocatepetl volcano reawakened in 1994, Mexican scientists needed people in the area who could be their eyes and ears. State police helped them find one, Nefi de Aquino, a farmer then in his 40s who lived beside the volcano. From that moment on, his life changed.
He became a police officer himself, but with a very specific job: watching Popocatepetl and reporting everything that he saw to authorities and researchers at diverse institutions.
For nearly three decades, de Aquino says he has been ''taking care of'' the volcano affectionately known as ''El Popo.'' And for the past 23 of those years, he has been sending scientists daily photographs.
Collaboration between researchers and local residents — usually people of limited means — is crucial to Mexico's volcano monitoring. Hundreds of villagers collaborate in different ways. Often local residents are the only witnesses to key events. Sometimes scientists install recording devices on their land, or have them collect ash samples.
One evening this week, the thin 70-year-old policeman with a hoarse voice stopped his patrol truck near the cemetery overlooking his home town, one of the area's best vantage points. At his feet lay the town of Santiago Xalitzintla. Directly in front at a distance of 14 miles (23 kilometers) sat Popocatepetl, puffing smoke, the rim of its crater aglow.
Since it appeared calm, de Aquino didn't stay long. Over the previous week, he had been busy sending digital volcano photographs to a slew of researchers at universities and government agencies as the mountain's activity increased and authorities raised the alert level. Once again the world's eyes were on the 17,797-foot Popocatepetl, including those of the 25 million people living within 60 miles of its crater.
On Friday, officials said the volcano's activity had decreased somewhat although they maintained the same alert level.
A farmer who was a meat packer for three years in Utah in his late 20s when he illegally emigrated to the United States, de Aquino's life took a radical turn one day in 1994 when someone in his home town told him police were looking for him.
At first he was afraid to go to the police, but eventually did. The interview was brief.
'''Do you know how to read?' 'Yes.' 'Write?' 'Yes.' 'Do you drive?' 'Yes.' 'Do you have a license?' 'Yes.' 'Heck, this one will work.'''
Officers told de Aquino that the government was looking for people to monitor the volcano and that he, then 41, had certain advantages. He appeared serious, he had finished high school and during his short stay in the United States he had learned how to take photographs.
At first he was given a volunteer civil defense role, and he took some courses at National Center for Disaster Prevention, or CENAPRED where he was ''immersed in the volcano.'' But he wasn't thrilled with doing the work without pay. So authorities offered to send him to the police academy.
Although de Aquino became an officer with some normal police duties, he was an odd cop. He almost always worked alone, patrolling remote mountain roads, taking photos of the volcano.
The ways that local people who help monitor the volcano are compensated are seldom straightforward, because they are not on the payrolls of universities or other research institutions, despite ''becoming our eyes close to the volcano,'' said Carlos Valdés, a researcher at the UNAM's Geophysics Institute and former head of CENAPRED.
As an example, Valdés said that the key person when the seismic monitoring system was installed on Popocatepetl was a mountain climber who lived in the town of Amecameca. The man, since deceased, knew the safest routes to climb and how to avoid putting instruments in locations that were sacred to locals.
The way to compensate the man, was ''to buy tires for his jeep, repair the vehicle, get him coats,'' because it was otherwise difficult to pay him.
Paulino Alonso, a technician at CENAPRED who does fieldwork at Popocatepetl, said collaboration with locals also has given researchers a better understanding of how locals perceive risks.
''A machine is never going to speak to the human perception of danger," Alonso said.
In 2000, when Popocatepetl grew more active, authorities declared a red alert and thousands of people were evacuated. De Aquino's monitoring work intensified.
''They gave me cameras, a patrol car and binoculars and every day I had to send three photos: one in the morning, one at midday and one at night,'' the policeman said.
He continues that work to this day, filling up his adobe-walled home with thousands of photographs. De Aquino lives alone on a modest ranch on the volcano's slopes, where he has some fruit trees growing beside a stream, and also raises corn and a few animals.
De Aquino helps keep locals informed about the volcano and assists during evacuations. Once, his house becomes an impromptu shelter for soldiers, police and government officials, he said.
De Aquino has gotten to go along on overflights of the crater, the first time terrified. ''You see the whole base, how it lights up, how its puts out smoke ... it felt strange," he said.
He has continued in his job despite being past retirement age.
''What I have learned from (Popocatepetl) is that while it's calm, it doesn't do anything, but when it gets mad, it goes crazy,'' he said.