But beyond the human tragedy, a new study found that Mary changed the make-up of forests covering more than half of the island, with some species falling after the storm and others rising.
And the research suggests that this could be a fate of changes that could come to the forests across many of the Atlantic body, as climate change drives more powerful storms.
A potential effect is that these forests, instead of being net powder stores, could actually become net carbon emitters, adding more carbon to the atmosphere. In other words, as forests are increasingly becoming victims of climate change, they will also contribute to it.
"Cold dynamics after a storm is hard to understand, but after a storm a forest loses much carbon and regenerates it as it regrows, so we look at the long-term average," said Maria Uriarte, Columbia University's Earth Institute, which led the research.
"If bad storms become the norm, if a storm of Mary's difficulty becomes the average storm in the Caribbean, we expect the forest to save less carbon because trees do not have time to grow large. We expect the net balance to be negative ̵
Damage and recovery
Uriarte has been studying Puerto Rico's trees for the past 15 years. She returned to the island three months after she named the hurricane and saw the damage to the forests personally.
"What was very striking is that with wood species that were winners and losers," she told CNN.
"I've been here a few times since the hurricane, and the recovery is very fast. There is much damage, but regrowth has come in – but the composition [of the forests] will certainly change."
For this latest study, published this week in the journal Nature Communications, Uriarte and her team were able to investigate the forest close to getting one more detailed view of the damage done.
Winners and Losers
They found that Maria killed twice as many trees as Hugo and Georges – both category 3 storms and much less intense than Maria – and broke more than three times as many suitcases. Many of those with broken suitcases will die over the next few years, according to Uriarte.
"One thing that was different between the storm is the percentage of trees that were broken," said Uriarte. "Really big trees that were just snapped in half – and this is unique."
For the researchers, this was a striking finding, as in the earlier larger trees – like mahogany-like "tabonucos", which are used to make furniture and boats and "ausubos", It is so dense that their wood does not float in water – has been more resistant to storms.
"These are some of the trees that have denser wood, and trees with very dense wood have historically very low pause and mortality," Uriarte said. "This storm was different – trees 100 years or more were broken. Some of these trees will be able to rebuild the biomass and recover, and some of them will not."
Exactly why these larger, denser trees, which are so badly trapped, are still being investigated. But the result is that the number of large hardwoods has fallen, while other species – especially fast-growing palms, bending into strong winds, rather than breaking – have replaced them.
Uriarte says that this change in the composition of forests could be something we see across the Atlantic currents – with the entire trees becoming shorter and less dense and the forests smaller biodiverse.
"Palm trees have less dense biomass than hardwoods, and they store less carbon," Uriarte says.
Yadvinder Malhi, a professor of ecosystem science at Oxford University who was not involved in the research, said it was likely to shift to more rapidly growing trees growing rapidly after a hurricane.
"In the long run, the total amount of stored carbon in the forest depends on the recovery time between disturbances "It falls to almost zero during the disturbance and slowly builds up and falls again," he said. "So if these disturbances become more frequent and more intense, then the average over a century time scale will be lower."
The study notes that "the expected changes in hurricane wind and precipitation can have serious consequences for the long-term resistance of tropical forests in the North Atlantic basin."
In addition to affecting carbon emissions "For example, the endangered Puerto Rican parrot, who likes old, high growth, cannot cope because much of the forest is disturbed," Uriarte said. Species that favor an open forest environment will do better, she adds.