University of Michigan ecologists Ivette Perfecto and John Vandermeer have studied Latin American coffee farms for a quarter century, and they tracked the recovery of tropical forests in Nicaragua following 1988’s Hurricane Joan for nearly 20 years.

So, when Hurricane Maria struck Puerto Rico as a Category 4 storm in September 2017, Perfecto and Vandermeer had certain expectations about the types and extent of damages the storm would inflict on the coffee industry, long a backbone of the island’s agricultural sector.

But when they analyzed data collected at 28 Puerto Rican coffee farms less than a year after Maria and compared it to 2013 data from the same farms, many of those expectations flew right out the window.

One of the biggest surprises: There was no link between the amount of shade on a coffee farm – a key measure of management intensity – and damage from the hurricane.

The expectation by Perfecto and Vandermeer going into the Hurricane Maria study was that shade trees would act as windbreaks and that damage to coffee plants would be less severe in these “agroforestry systems” than at farms without trees.

While most of the Puerto Rican coffee farms did lose a great deal of shade cover—an average of 37.5% canopy loss – there was “no relationship” between the amount of shade on a farm and damage to its coffee plants, the researchers report in a study scheduled for publication Oct. 30 in Scientific Reports, a Nature journal.

Instead, the researchers observed an enormous amount of variability.

One possible explanation: Yes, the wind-shielding effect of shade trees is real, but it has limits. Maria was the strongest hurricane to hit Puerto Rico since 1928, with sustained winds of 155 mph.

“Canopy cover with relatively large shade trees is likely to be effective at providing some windbreak protection of coffee plants,” said Perfecto, a professor at the U-M School for Environment and Sustainability and first author of the study. “But when winds are so strong, those trees are toppled, and their trunks and canopies can do considerable damage to the coffee trees below.”

In addition to Perfecto and Vandermeer, who is a professor in the U-M Department of Ecology and Evolutionary Biology, other authors are Zachary Hajian-Forooshani, Nicholas Medina, Chatura Vaidya and Alexa White of the U-M Department of Ecology and Evolutionary Biology; Aaron Iverson of St. Lawrence University; Amarilys Irizarry of the U-M School for Environment and Sustainability; and Javier Lugo-Perez of Universidad de Puerto Rico, Utuado.

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Nature > Scientisfic Reports study: Response of Coffee Farms to Hurricane Maria: Resistance and Resilience from an Extreme Climatic Event