The benefits of hurricanes

My cousin, who is a soybean farmer in Northwest Indiana, complained to me this past Memorial Day weekend that he had never seen conditions so dry this time of year. The water level of the Tippecanoe River was the lowest he could remember, and the soybeans he'd planted were in serious danger of sharply reduced yields due to the drought.

Help came to his crops from an unusual source for Indiana--a tropical storm. While hurricanes and tropical storms make up an important part of the yearly rainfall budget in places like the Southeast U.S. and Japan, it is rare for the moisture from these storms to make a difference in inland locations, like Indiana. However, the image below, taken from the National Drought Mitigation Center, shows that Arlene, which dropped 2 - 3 inches of rain over much of Indiana on June 11, sharply reduced drought conditions there and in surrounding states.



Hurricanes and tropical storms are usually seen as terrible destructive forces of nature. However, they are an integral part of nature, and life in hurricane-prone areas has evolved to adapt to these great storms and even benefit from them. As we've seen, they can bring drought-busting rains. They can also perform the same cleansing function as forest fires in maintaining the conditions needed for healthy coastal forests, particulary in swampy mangrove forests. The intense rainfall of tropical cyclones causes high soil runoffs, resulting in high sediment levels being deposited in estuaries threatened by rising sea levels. Hurricane storm surges also carry substantial amounts of sediments and nutrients in coastal marshes. Studies show that hurricanes cause little long-term damage to marshes. While foliage may be stripped, the stimulation from new nutrients brought by the hurricane quickly returns the marshes to their original condition.

That being said, my cousin has a reason to be concerned about the negative impacts of Tropical Storm Arlene on his crops. The reason? Tropical cyclones are notorious spreaders of non-native invasive plants--in this case, a damaging fungus called soybean rust. Soybean rust, which spread from Asia to the Caribbean in recent years, first appeared in Alabama, Florida, Georgia, and six surrounding states in November 2004. It is thought to have been blown in from the Caribbean by Hurricane Ivan. There is concern that the winds of Arlene may have been strong enough to spread the spores as far north as Indiana, so my cousin's crops may have to adapt to deal with both the good and bad effects of Arlene.

Dr. Jeff Masters