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Will more powerful hurricanes threaten disappearing forests?

March 29, 2019

MIAMI (AP) — When Hurricane Maria sacked Puerto Rico, it did more than take thousands of lives, pulverize houses and dismantle infrastructure. It shredded the island’s tropical forests at an unprecedented rate.

The fierce Category 5 storm, the 10th most intense on record packing ferocious 155 mph winds when it roared ashore, felled trees at twice the rate of previous storms. Some species suffered damage 12 times higher. Now, with a warming planet expected to produce even more storms like Maria, the planet’s tropical forests are likely to be inexorably altered, according to a new study published Monday in the journal Nature Communications.

“These hurricanes are going to kill more trees. They’re going to break more trees,” Maria Uriarte, lead author and Columbia University’s Earth Institute biologist, said in a statement. “Forests will become shorter and smaller, because they won’t have time to regrow, and they will be less diverse.”

For South Florida, where development has already wiped out much of the pine rocklands and hardwood hammocks that once covered high ground, that could be a death knell. Intense hurricanes have already taken a toll on pine rockland: Hurricane Wilma blasted through one of the few last stands in the Keys on Sugarloaf in 2005. Irma delivered what might be a fatal blow, say Florida International University ecologists trying to understand why the pine rockland has failed to recover.

When Maria hit Puerto Rico, it dumped up to three feet of rain in places, in addition to lashing the island with punishing winds. Many trees were stripped of leaves, snapped in two or uprooted entirely. The storm was the strongest to hit the island since 1928, the study pointed out.

Uriarte, who has been researching island forests for the past 15 years, zeroed in on a 40-acre area of El Yunque National Forest for this study. The area has been monitored since 1990, so had a trove of data from past hurricanes, including Hugo and Georges, both Category 3 storms.

Maria, she found, killed twice as many trees. Many were among the forest’s slowest growing hardwoods, including soaring tabonucos, or candlewoods, topped by broad canopies, and ausubos, also called bulletwood, with wood too dense to float. Uriarte said these lofty trees provide habitat in the forest for birds and other animals that ignore smaller trees. Most had survived past storms, but Maria plowed them down. About half the trees with broken trunks are expected to die, she said.

While hardwoods fell, Uriarte found skinnier, more flexible trees, including sierra palms, did better. With more intense storms, it’s likely these trees will become more numerous and could change the makeup of the forest.

More downed trees also mean forests may no longer provide one of their biggest benefits to address climate change: soaking up carbon blamed for heating the planet. Instead, dead trees could start emitting carbon, Uriarte said. Fast-growing smaller trees that are more likely to be knocked down by storms could also become more plentiful, adding even more carbon, she said.

“The factors that protected many trees in the past,” Uriarte said, “will no longer apply.”

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Information from: The Miami Herald, http://www.herald.com