Nav: Home

Hurricane Maria study warns: Future climate-driven storms may raze many tropical forests

March 25, 2019

A new study shows that 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. Biodiversity could suffer as result, and more carbon could be added to the atmosphere, say the authors. The study appears this week in the journal Nature Communications.

Hurricane Maria not only destroyed far more trees than any previously studied storm; big, old trees thought to be especially resistant to storms suffered the worst. Lead author Maria Uriarte, a faculty member of Columbia University's Earth Institute, said that because hurricanes are projected to intensify with warming climate, the damage probably presages more such events. "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," she said. "Forests will become shorter and smaller, because they won't have time to regrow, and they will be less diverse."

When Maria hit Puerto Rico in October 2017, it came in as a Category 4, with winds up to 155 miles per hour and up to three feet of rain in places. Many trees were denuded of foliage, snapped in half or blown clear out of the ground. The strongest storm to hit the island since 1928, Maria killed or severely damaged an estimated 20 million to 40 million trees.

Uriarte, who has been monitoring tree growth and mortality across Puerto Rico for the past 15 years, returned soon after the hurricane and began documenting its effects. For the new study, she and two colleagues homed in on a 40-acre section of the El Yunque National Forest, near the capital of San Juan, that has been intensively monitored by multiple teams since 1990. This long-term monitoring allowed Uriarte and her colleagues to compare damage from Maria with that of past hurricanes, including 1989's Hurricane Hugo and 1998's Hurricane Georges--Category 3 storms, but the only things even close to Maria in recent times.

They found that Maria killed twice as many trees outright as previous storms, and broke more than three times as many trunks. Some species suffered much worse, with breakage rates up to 12 times those of previous storms. Alarmingly, 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. 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, said Uriarte.

However, a few species did well in all the storms, and one stood out: the common sierra palm, whose slender, flexible trunk bends with wind and quickly resprouts, grass-like, from its top if it loses foliage. Uriarte believes that the palms and a few pioneer species that can take root quickly and grow following storms may be the future of forests across the Atlantic tropics and subtropics. "This will yield lower statured and less diverse forests dominated by a few resistant species," she said.

Tropical cyclones derive their energy from ocean heat. Atlantic temperatures are already ascending, and models predict that by 2100, maximum sustained hurricane winds could increase by as much as 15 percent. Warmer air also carries more moisture, so rainfall could increase by up to 20 percent near storm centers. Both factors destroy trees; extreme winds do it directly, while rain saturates and destabilizes soil, encouraging uprooting. "The expected changes in hurricane winds and rainfall may have profound consequences for the long-term resilience of tropical forests in the North Atlantic basin," says the study.

The potential loss of many tree species 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. This would be because the decay of felled trees would outweigh carbon taken in by any replacements. 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. Separate estimates suggest that trees killed or damaged by Hurricane Maria alone will release about 5.75 million tons of carbon to the atmosphere, or about 2.5 percent of the carbon taken up annually by all forests in the United States.

Edmund Tanner, a senior lecturer emeritus at the University of Cambridge who studies tropical trees but was not involved in the new research, said the study is important, because "it reports different, rather than just intensified, effects of strong versus weaker hurricanes." Tanner said 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," noted Tanner. "There is a Category 5."
The study was coauthored by two researchers who have long worked in the El Yunque forest: Jill Thompson, a plant ecologist at the Centre for Ecology & Hydrology in the United Kingdom; and Jess K. Zimmerman, a professor at the University of Puerto Rico in San Juan. The research was funded by the U.S. National Science Foundation.



The paper is "Hurricane Maria Tripled Stem Breaks and Doubled Tree Mortality Relative to Other Major Storms," DOI 10.1038/s41467-019-09319-2

Scientist contact:

Maria Uriarte:

More information: Kevin Krajick, Senior editor, science news, The Earth Institute 212-854-9729

The Earth Institute, Columbia University mobilizes the sciences, education and public policy to achieve a sustainable earth.

Earth Institute at Columbia University

Related Hurricane Articles:

2017 hurricane season follows year of extremes
2016 hurricane season started in January and ended 318 days later in late-November.
Study Offers New Insight on Hurricane Intensification
In a new study, researchers from the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science showed the first direct observations of hurricane winds warming the ocean surface beneath them due to the interactions with currents from an underlying warm-water whirlpool.
NASA provides a 3-D look at Hurricane Seymour
Hurricane Seymour became a major hurricane on Oct. 25 as the Global Precipitation Measurement mission or GPM core satellite analyzed the storm's very heavy rainfall and provided a 3-D image of the storm's structure.
NASA sees Hurricane Seymour becoming a major hurricane
Hurricane Seymour was strengthening into a major hurricane in the Eastern Pacific Ocean when the NASA-NOAA Suomi NPP satellite passed over it from space.
NASA animation shows Seymour becomes a hurricane
Tropical Depression 20 formed in the Eastern Pacific Ocean on Sunday and by Monday at 11 a.m. it exploded into a hurricane named Seymour.
Hermine becomes a hurricane in the Gulf of Mexico
Tropical Storm Hermine officially reached hurricane status on Thursday, Sept.
NASA spies major Hurricane Georgette
Hurricane Georgette is a major hurricane in the Eastern Pacific Ocean.
NASA peers into major Hurricane Blas
As NASA satellites gather data on the first major hurricane of the Eastern Pacific Ocean hurricane season, Blas continues to hold onto its Category 3 status on the Saffir Simpson Wind Scale.
NASA gets an eyeful of Hurricane Blas
Satellites eyeing powerful Hurricane Blas in the Eastern Pacific Ocean revealed a large eye as the powerful storm continued to move over open waters.
Early use of 'hurricane hunter' data improves hurricane intensity predictions
Data collected via airplane when a hurricane is developing can improve hurricane intensity predictions by up to 15 percent, according to Penn State researchers who have been working with the National Oceanic and Atmospheric Administration and the National Hurricane Center to put the new technique into practice.

Related Hurricane Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Do animals grieve? Do they have language or consciousness? For a long time, scientists resisted the urge to look for human qualities in animals. This hour, TED speakers explore how that is changing. Guests include biological anthropologist Barbara King, dolphin researcher Denise Herzing, primatologist Frans de Waal, and ecologist Carl Safina.
Now Playing: Science for the People

#SB2 2019 Science Birthday Minisode: Mary Golda Ross
Our second annual Science Birthday is here, and this year we celebrate the wonderful Mary Golda Ross, born 9 August 1908. She died in 2008 at age 99, but left a lasting mark on the science of rocketry and space exploration as an early woman in engineering, and one of the first Native Americans in engineering. Join Rachelle and Bethany for this very special birthday minisode celebrating Mary and her achievements. Thanks to our Patreons who make this show possible! Read more about Mary G. Ross: Interview with Mary Ross on Lash Publications International, by Laurel Sheppard Meet Mary Golda...