Wind may have been pointed as the main culprit for the knocked down trees in all the attacks of hurricanes. However, a new survey was recently released of the damage in the Puerto Rican forests following the back-to-back hurricanes back in 2017. This particular survey highlighted the power of a heavy downpour.
When Hurricane Irma hit the coast of Puerto Rico in the first week of September in 2017, the storm resulted in heavy rains. Nevertheless, despite the strong downpour, it didn't cause too much damage. Another hurricane named, Maria, which hit the same area two weeks after, was said to be a different story.
Hurricane Maria was recorded as the "strongest hurricane" to land directly in Puerto Rico in almost 100 years. Being the strongest to make a direct landfall in the country, Maria brought fast wind speeds of more than 200 kilometers per hour.
It also dropped almost 1.5 meters of heavy rains in two days straight, in some Puerto Rican areas. Through the use of on-the-ground observations and satellite images at approximately 25 plots within the United States territory, a group of researchers plotted the devastation which the two storms caused.
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Total Forest Biomass Destroyed
A projected 10.44 million metric tons, or around 23 percent, of the total forest biomass of Puerto Rico, was devastated. However, the level of damage, differ according to location. This was reported by the researchers online via Scientific Reports on March 9.
Making a comparison between the fractions of lost forest and other local factors like rain exposure and wind during the wrath of the hurricanes, showed that severe impairment was more closely linked with heavy rains than strong winds during Hurricane Maria.
Ecologist at the Columbia University, Maria Uriarte said, the comparison of fractions was not something that she was expecting. She added, she thought, "the big driver would be wind." The rainfall which Hurricane Maria brought, according to Uriarte, could have played a vital role in the collapsing trees by "pressing down on tree coverings" while the soil gets loosened.
Severely damaged areas tended to be the places, as well that were strongly hit with heavy rains which Hurricane Irma brought, and had the soil that could hold abundant water. This then, suggests, regions drenched this particular hurricane were geared up to experience more serious impairment from Maria.
Rain as the Culprit
The counterintuitive research finding that rain, indeed played a more vital role, compared to wind, in this forest impairment recommends tools and mechanisms for predicting effects of tropical storms that may need to provide more weight to the downpour.
This was according to Weimin Xi, a Texas A&M University ecologist. Xi was not part of the said research study, though. This may be particularly essential as the warming environment is expected to develop hurricanes like Irma and Maria with much heavier rains and stronger winds.
Moreover, super-strong hurricanes in the future might have other consequences that are unexpected for tropical forests. In relation to this, research which Nature Communications published in March 2019, Uriarte's team examined further the tree damage in the similar forest found in the northeastern part of Puerto Rico following the occurrence of Category 5 storm, Hurricane Hugo as it hit Puerto Rico in 1989.
Nevertheless, larger trees that have denser wood were proven to be more resilient to smashing during Hugo, and, as anticipated, these species were not quite more robust during Maria. Instead, more flexible trees, like palms, found to have endured and survived against Hurricane Maria sans breaking.