Alien Trees Destroying Native Hawaiian Forests

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(See photos of other species invading the United States.)

The study appears this week in the journal Proceedings of the National Academy of Sciences.

Other Impacts

In addition to reducing rain forest diversity, the researchers say, invaders affect the basic life-giving services that forests provide to people.

"For example, we have shown that these particular invasive species change the amount of carbon stored in ecosystems [rather than in our atmosphere]," Asner said.

In other words, more carbon dioxide—a major greenhouse gas—could end up in the atmosphere instead of stored in the forests' natural "sink."

"Even more striking," Asner said, is that the invasive trees "negatively affect the recreational and cultural resources provided by native forests to people living there."

For instance some of the alien trees create an impenetrable layer of vegetation that makes it hard to access the forest for activities such as hiking, Asner said.

Also, invasives "shade out" some of the native tree species that are used in traditional Hawaiian ceremonies.

Julie Denslow, an ecologist at the U.S. Department of Agriculture's Institute of Pacific Islands Forestry, was not involved in the study.

"This is one of the first illustrations of the impacts of invasive species on native, intact tropical forest at a large scale," she said.

"It highlights the vulnerability of protected areas to invasive species and the need for aggressive management to maintain conservation values."

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