Millions Of Years Of Cicada Survival Could Be Ending As Forests Disappear

Periodical cicadas could be heading toward extinction as the loss of old-growth forests leaves them without the roots they depend on for food during their years underground.

Biologists at the University of Iowa found that replacing old, intact forests with new trees does not allow the insects to recover easily. Periodical cicadas move slowly into new habitats, limiting their ability to reclaim lost territory.

There are seven periodical cicada species in North America, with four following 13-year cycles and three emerging every 17 years. They spend most of their lives underground before appearing together in enormous numbers.

Their survival depends on overwhelming abundance because they have no known defenses against predators. Birds and small mammals can consume them in large numbers during their mass emergences.

Researchers found that the insects spread about 50 yards on average during each emergence. Modeling showed that even under the best conditions, recolonizing restored forests could take many centuries.

A relocation experiment involving 20,000 Brood XIII cicadas ended within a week, as the vast majority were eaten by predators.

“There is one ray of hope, though,” Forbes said. Forested preserves containing periodical cicada broods could allow the species to survive and slowly disperse, provided new forests remain intact and are not cut down.