The Positive Effects Of Rain From Hurricanes

May 30, 2016

As Hurricane season begins this week, there’s something to keep in mind. Although these storms are known for bad things like strong winds, heavy rain, downed trees, flooding, and power outages. There may be an upside. Researchers at Duke University say they can bring much-needed rain during droughts. 

Environmental engineering professor Ana Barros first got the idea to study the effect of rain from tropical systems in 2006, when she saw a TV news story about that year’s drought in the southeastern U.S. The reporter talked to farmers who said their crops were in "very bad shape."

"The headline actually said 'what we need is a really good hurricane,'" she recalls, "and I thought that was really interesting, right? What is a 'good' hurricane?"

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What the farmers meant was the rain from the hurricane might be able to help salvage some of their crops. Maybe the farmers were onto something, Barros thought. So she and her team of researchers came up with a way to model how rainfall affects photosynthesis in plants. Plants are more efficient at turning carbon dioxide into the energy they need to grow when they have enough water. They ran that model on rainfall data from the Southeastern U.S. from 1980 through 2007. Barros’s team concluded in years when tropical storms or hurricanes made landfall, there was, in fact, more photosynthesis going on.

"They produce so much water input, that actually replenishes soil moisture content in the piedmont and that recharges aquifers and so on," she says. "They play a very important role in busting droughts, basically, and in maintaining the systems functional for ecosystems."

In fact, she says the amount of carbon uptake generated by a hurricane through photosynthesis is "hundreds of times" that of the output of all vehicles in the U.S. in a given year.

"And so what this means is that this landscape [the Southeastern U.S.] is very well adapted to these kinds of events in the warm season of course, when the soil moisture and the aquifers need this additional output," Barros says.

But too many strong storms aren’t good for the plants. In years when storms are too frequent, the ground becomes saturated, and there can be flooding. Barros also warns that the positive effect of hurricanes would diminish if more forests are cut down in the Southeast---and the chance of flooding would increase.