Hurricane Maria Inflicted Tree Damage Unprecedented in Modern Times

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CC BY 4.0. D. Morton, NASA / via Nature Communications

A new study finds that the storm killed or severely damaged up to 40 million trees in Puerto Rico; suggests future storms could forever alter forests across the Atlantic tropics.

We all know how devastating Hurricane Maria was to Puerto Rico. Roaring onto the island in October 2017 as a Category 4 storm with winds up to 155 miles per hour and up to three feet of rain in places – it was the strongest storm to hit Puerto Rico since 1928.

Aerial photos immediately after showed a once verdant island stripped of green. How much of that was defoliation versus toppled trees? A new study/tree census has the answer, and it’s not good news.

The study, led by Maria Uriarte, a faculty member of Columbia University's Earth Institute, found that the damage inflicted on trees in Puerto Rico by Hurricane Maria was “unprecedented in modern times, and suggests that more frequent big storms whipped up by a warming climate could permanently alter forests not only here, but across much of the Atlantic tropics,” according to the University.

“Biodiversity could suffer as result, and more carbon could be added to the atmosphere,” say the authors.

Not only did Maria harm more trees than any other storm studied before, but the types of trees that were damaged also raise concerns.

The researchers found that Maria killed two times as many trees outright as previous storms, and broke more than three times as many trunks. For some species it was even worse, with breakage rates up to 12 times those of previous storms. Alarmingly, large, established trees – the ones assumed to be stalwart in storms – suffered the worst.

“These tended to be the slowest-growing, most valuable hardwoods that in the past were the most resilient to big storms: towering mahogany-like tabonucos with great crowns, prized for furniture and boat-building, and thick ausubos, whose wood is so dense it does not float in water,” said Uriarte. “These and other big trees provide habitat for many birds and other creatures that smaller trees do not. About half of the trees with broken trunks will die within two to three years.”

With projections that hurricanes will becomes more intense with warming temperatures, the outlook for forests in the region isn’t so great.

"These hurricanes are going to kill more trees. They're going to break more trees. The factors that protected many trees in the past will no longer apply," Uriarte said. "Forests will become shorter and smaller, because they won't have time to regrow, and they will be less diverse."

These is, however, a few species that fared better than the rest. I have always marveled at how palm trees survive hurricanes (and wrote about it here: How do palm trees survive hurricanes). As it turns out, the common sierra palm managed to fare not so terribly in the face of Maria’s wrath. Uriarte thinks that the palms and a few other species that can recover quickly after storms may be the future of forests across the Atlantic tropics and subtropics.

As we all know that ecosystems are delicately engineered things that rely on most of their parts working in harmony, the loss of so many trees could have cascading effects on forest wildlife and plants, say the researchers.

“This also would probably alter forests' growth dynamics, such that instead of soaking in more atmospheric carbon than they give off--which they currently do--the equation would reverse, and forests would become net emitters,” they say.

To what do we owe that dismal math? The decay of downed trees would outweigh carbon taken in by any replacements, notes the researchers. “Along with palms, one species that probably would take over would be the fast-growing yagrumo, which shoots up quickly in sunny clearings created by big storms. But the yagrumo also is often the first to fall in storms, and so would just add to the problem. Thus, forests would help feed the very warming that is destroying them.”

As one tropical tree expert told the University, the findings of the effects are "probably representative of huge areas of tropical lowland forest near sea coasts, some of which are likely to experience similar or worse damage in a warming world." Maria "was a Category 4 hurricane," he said. "There is a Category 5." And I shudder to think, it might not end there.

You can read more and learn how they conducted the census in Nature Communication.