On this day in 2017, Hurricane Maria made landfall in Puerto Rico as a Category 4 storm. The satellite image below shows the eye over the eastern end of the island that morning.
The official death toll stood at 64 for months. Later studies put it at about 2,975. The difference is not a correction of arithmetic but a change in what was counted. A death certificate records an immediate cause, and in the weeks after a storm that cause is often kidney failure without dialysis, sepsis, a heart attack when no ambulance can reach the road. Researchers therefore used excess mortality: they took the number of deaths recorded in the months after September 2017 and compared it with the number that would ordinarily have been expected in that population at that time of year. The gap between the two is the estimate.
It is a method built for exactly this, when the harm arrives slowly and through hospitals, water supplies and electricity rather than wind alone. About 2,975 people in Puerto Rico did not survive that season. The counting was done carefully so that they would be counted.
Ada, thank you for setting out the method so plainly. Worth adding that for many households the power did not come back for months rather than days, and the last customers were not reconnected until well into the following year.
The forests were counted too, Ada. El Yunque lost most of its canopy in a few hours, and the bird surveys that followed were carried out largely by local volunteers and forest staff walking the wrecked trails, checking which species had come back and which had not.